discovery-api/Overview.src.html
author Rich Tibbett <richt@opera.com>
Tue, 02 Oct 2012 19:29:45 +0200
changeset 243 220f3226b2a1
parent 241 985e203d74f7
child 250 8b912f2bb9c7
permissions -rw-r--r--
Apply pub rules to proposed Working Draft update
     1 <!DOCTYPE html>
     2 <!--
     3 
     4   THIS IS THE WORKING VERSION OF THE CURRENT SPECIFICATION!
     5 
     6   This specification is built using ReSpec.js <http://dev.w3.org/2009/dap/ReSpec.js/documentation.html>
     7 
     8   From time to time it's necessary to HTML5 Tidy this document using the tool @ <http://w3c.github.com/tidy-html5/>.
     9 
    10   The command used to format this document (Overview.src.html) is as follows (replacing all = signs with - signs!):
    11 
    12   @> tidy ==new-blocklevel-tags section ==char-encoding utf8 ==tidy-mark no ==indent yes ==indent-spaces 2 ==indent-attributes yes ==wrap 120 ==fix-bad-comments yes -m Overview.src.html
    13 
    14   To publish a new compiled version (Overview.html), we need to open this file (Overview.src.html) in any web browser.
    15   Once it has loaded we press 'Ctrl + Shift + S' (or 'Cmd' + 'Shift' + 'S' on Mac) and then select
    16   'Save as HTML (Source)' from the resulting menu.
    17 
    18   We then replace Overview.html with the produced HTML source of this process.
    19 
    20   Next we run HTML5 Tidy over our new Overview.html file with the following command (replacing all = signs with - signs!):
    21 
    22   @> tidy ==new-blocklevel-tags section ==char-encoding utf8 ==tidy-mark no ==indent yes ==indent-spaces 2 ==indent-attributes yes ==wrap 120 ==hide-comments yes -m Overview.html
    23 
    24   Now the specification is ready to be published :)
    25 
    26 -->
    27 <html>
    28   <head>
    29     <title>
    30       Network Service Discovery
    31     </title>
    32     <meta http-equiv='Content-Type'
    33           content='text/html; charset=utf-8'>
    34     <script type="text/javascript"
    35           class='remove'>
    36 var respecConfig = {
    37           specStatus:   "ED",
    38           //publishDate:  "2012-10-09",
    39           shortName:    "discovery-api",
    40           edDraftURI:   "http://dvcs.w3.org/hg/dap/raw-file/tip/discovery-api/Overview.html",
    41           previousMaturity: "FPWD",
    42           previousPublishDate: "2012-08-07",
    43           editors: [
    44             {
    45               name:       "Rich Tibbett",
    46               //url:        "http://richt.me/",
    47               company:    "Opera Software ASA",
    48               companyURL: "http://opera.com/"
    49             },
    50             {
    51               name:       "Clarke Stevens",
    52               //url:      "",
    53               company:    "CableLabs",
    54               companyURL: "http://cablelabs.com/"
    55             }
    56           ],
    57           noIDLIn:      true,
    58           wg:           "Device APIs Working Group",
    59           wgURI:        "http://www.w3.org/2009/dap/",
    60           wgPublicList: "public-device-apis",
    61           wgPatentURI:  "http://www.w3.org/2004/01/pp-impl/43696/status"
    62       };
    63     </script>
    64     <script src='http://www.w3.org/Tools/respec/respec-w3c-common'
    65           type="text/javascript"
    66           class='remove'
    67           async="">
    68 </script>
    69     <style type="text/css">
    70 /* Custom ReSpec CSS (by Rich Tibbett) */
    71 
    72       /* Add better spacing to sections */
    73       section, .section { margin-bottom: 2em; }
    74 
    75       /* Reduce note & issue render size */
    76       .note, .issue { font-size:0.8em; }
    77 
    78       /* Add addition spacing to <ol> and <ul> for rule definition */
    79       ol.rule li, ul.rule li { padding:0.6em; }
    80 
    81       pre.widl { border: solid thin; background: #EEEEEE; color: black; padding: 0.5em 1em; position: relative; }
    82       pre.widl :link, pre.widl :visited { color: #000; background: transparent; }
    83       pre.widl:before { content: "IDL"; font: bold small sans-serif; padding: 0.5em; background: white; position: absolute; top: 0; margin: -1px 0 0 -4em; width: 1.5em; border: thin solid; border-radius: 0 0 0 0.5em }
    84 
    85       div.example { border: solid thin red; background: #F7DFE5; color: black; padding: 0.5em 1em; position: relative; margin: 1em 0 1em 4.6em; width: auto; }
    86       div.example:before { content: "EXAMPLE"; font: bold small sans-serif; padding: 0.5em; background: red; color: white; position: absolute; top: 0; margin: -1px 0 0 -7.6em; width: 5em; border: thin solid red; border-radius: 0 0 0 0.5em }
    87 
    88       dl.domintro { color: green; margin: 2em 0 2em 2em; padding: 0.5em 1em; border: none; background: #DDFFDD; }
    89       hr + dl.domintro, div.impl + dl.domintro { margin-top: 2.5em; margin-bottom: 1.5em; }
    90       dl.domintro dt, dl.domintro dt * { color: black; text-decoration: none; }
    91       dl.domintro dd { margin: 0.5em 0 1em 2em; padding: 0; }
    92       dl.domintro dd p { margin: 0.5em 0; }
    93       dl.domintro code {font-size: inherit; font-style: italic; }
    94       dl.domintro:before { display: table; margin: -1em -0.5em 0.5em auto; width: auto; content: 'This box is non-normative. Implementation requirements are given below this box.'; color: red; border: solid 2px; background: white; padding: 0 0.25em; }
    95 
    96       table { border-collapse:collapse; border-style:hidden hidden none hidden }
    97       table thead { border-bottom:solid }
    98       table tbody th:first-child { border-left:solid }
    99       table td, table th { border-left:solid; border-right:solid; border-bottom:solid thin; vertical-align:top; padding:0.2em }
   100     </style>
   101   </head>
   102   <body>
   103     <section id='abstract'>
   104       <p>
   105         This specification defines a mechanism for an HTML document to discover and subsequently communicate with
   106         <abbr title="Hypertext Transfer Protocol">HTTP</abbr>-based services advertised via common discovery protocols
   107         within the current network.
   108       </p>
   109     </section>
   110     <section id='sotd'>
   111       <p>
   112         This document represents the early consensus of the group on the scope and features of the proposed API.
   113       </p>
   114     </section>
   115     <section class="informative">
   116       <h3>
   117         Introduction
   118       </h3>
   119       <p>
   120         To enable Web pages to connect and communicate with Local-networked Services provided over HTTP, this
   121         specification introduces the <a href="#navigatornetworkservice"><code>NavigatorNetworkService</code></a>
   122         interface.
   123       </p>
   124       <p>
   125         Using this <abbr title="Application Programming Interface">API</abbr> consists of requesting a well-known
   126         service type, known by developers and advertised by Local-networked Devices. User authorization, where the user
   127         connects the web page to one or more discovered services, is expected before the web page is able to interact
   128         with any Local-networked Services.
   129       </p>
   130       <p>
   131         A web page creates a request to obtain connectivity to services running in the network by specifying a
   132         well-known discovery service type that it wishes to interact with.
   133       </p>
   134       <p>
   135         The user agent, having captured all advertised services on the network from the Service Discovery mechanisms
   136         included in this recommendation, attempts to match the requested service type to a discovered service according
   137         to the processing described herein.
   138       </p>
   139       <p>
   140         If a service connectivity request is successful then the Web page is provided with the necessary information to
   141         communicate with the authorized Local-networked Service. If the request fails then the Web page will receive an
   142         error callback containing an error code describing the cause of Local-networked Service connectivity failure.
   143       </p>
   144       <p>
   145         Once connected to a Local-networked Service the Web page can send requests and receive responses to the
   146         Local-networked Service via the messaging format and appropriate channel inferred from the service type
   147         authorized via the provided API. The Web page, once connected, can also receive service-pushed events, in the
   148         messaging format supported by the Local-networked Device, if such event subscription functionality is provided
   149         by the connected Local-networked Service.
   150       </p>
   151       <div class="example">
   152         <p>
   153           Example of requesting a DNS-SD advertised service:
   154         </p>
   155         <hr>
   156         <pre class="highlight">
   157 function showServices( services ) {
   158   // Show a list of all the services provided to the web page
   159   for(var i = 0, l = services.length; i &lt; l; i++) console.log( services[i].name );
   160 }
   161 
   162 navigator.getNetworkServices('zeroconf:_boxee-jsonrpc._tcp', showServices);
   163 </pre>
   164       </div>
   165       <div class="example">
   166         <p>
   167           Example of requesting a UPnP advertised service, also handling error conditions:
   168         </p>
   169         <hr>
   170         <pre class="highlight">
   171 function showServices( services ) {
   172   // Show a list of all the services provided to the web page
   173   for(var i = 0, l = services.length; i &lt; l; i++) console.log( services[i].name );
   174 }
   175 
   176 function error( e ) {
   177   console.log( "Error occurred: " + e.code );
   178 }
   179 
   180 navigator.getNetworkServices('upnp:urn:schemas-upnp-org:service:ContentDirectory:1', showServices, error);
   181 </pre>
   182       </div>
   183       <div class="example">
   184         <p>
   185           Example of requesting either a DNS-SD or UPnP advertised service:
   186         </p>
   187         <hr>
   188         <pre class="highlight">
   189 function showServices( services ) {
   190   // Show a list of all the services provided to the web page (+ service type)
   191   for(var i = 0, l = services.length; i &lt; l; i++)
   192      console.log( services[i].name + '(' + services[i].type + ')' );
   193 }
   194 
   195 navigator.getNetworkServices([
   196   'zeroconf:_boxee-jsonrpc._tcp',
   197   'upnp:urn:schemas-upnp-org:service:ContentDirectory:1'
   198 ], showServices);
   199 </pre>
   200       </div>
   201       <p>
   202         For more detailed examples see the <a href="#examples">Examples</a> section.
   203       </p>
   204     </section>
   205     <section id='conformance'>
   206       <p>
   207         Requirements phrased in the imperative as part of algorithms (such as "strip any leading space characters" or
   208         "return false and abort these steps") are to be interpreted with the meaning of the key word ("must", "should",
   209         "may", etc) used in introducing the algorithm.
   210       </p>
   211       <p>
   212         Some conformance requirements are phrased as requirements on attributes, methods or objects. Such requirements
   213         are to be interpreted as requirements on user agents.
   214       </p>
   215       <p>
   216         Conformance requirements phrased as algorithms or specific steps MAY be implemented in any
   217         manner, so long as the end result is equivalent. (In particular, the algorithms defined in this specification
   218         are intended to be easy to follow, and not intended to be performant.)
   219       </p>
   220       <p>
   221         The only conformance class defined by this specification is a <dfn>user agent</dfn>.
   222       </p>
   223       <p>
   224         User agents MAY impose implementation-specific limits on otherwise unconstrained inputs,
   225         e.g. to prevent denial of service attacks, to guard against running out of memory, or to work around
   226         platform-specific limitations.
   227       </p>
   228       <p>
   229         When support for a feature is disabled (e.g. as an emergency measure to mitigate a security problem, or to aid
   230         in development, or for performance reasons), user agents MUST act as if they had no support
   231         for the feature whatsoever, and as if the feature was not mentioned in this specification. For example, if a
   232         particular feature is accessed via an attribute in a Web IDL interface, the attribute itself would be omitted
   233         from the objects that implement that interface - leaving the attribute on the object but making it return null
   234         or throw an exception is insufficient.
   235       </p>
   236       <section>
   237         <h3>
   238           Dependencies
   239         </h3>This specification relies on several other underlying specifications.
   240         <dl>
   241           <dt>
   242             HTML
   243           </dt>
   244           <dd>
   245             Many fundamental concepts from HTML are used by this specification. [[!HTML5]]
   246           </dd>
   247           <dt>
   248             WebIDL
   249           </dt>
   250           <dd>
   251             The IDL blocks in this specification use the semantics of the WebIDL specification. [[!WEBIDL]]
   252           </dd>
   253         </dl>
   254       </section>
   255     </section>
   256     <section>
   257       <h3>
   258         Terminology
   259       </h3>
   260       <p>
   261         The construction "a <code>Foo</code> object", where <code>Foo</code> is actually an interface, is sometimes
   262         used instead of the more accurate "an object implementing the interface <code>Foo</code>".
   263       </p>
   264       <p>
   265         The term DOM is used to refer to the API set made available to scripts in Web applications, and does not
   266         necessarily imply the existence of an actual <code>Document</code> object or of any other <code>Node</code>
   267         objects as defined in the DOM Core specifications. [[!DOM4]]
   268       </p>
   269       <p>
   270         An IDL attribute is said to be <em>getting</em> when its value is being retrieved (e.g. by author script), and
   271         is said to be <em>setting</em> when a new value is assigned to it.
   272       </p>
   273       <p>
   274         A <dfn>valid service type</dfn> is a string that begins with <code>upnp:</code> or <code>zeroconf:</code>
   275         followed by one or more characters in the ranges U+0021, U+0023 to U+0027, U+002A to U+002B, U+002D to U+002E,
   276         U+0030 to U+0039, U+0041 to U+005A, U+005E to U+007E.
   277       </p>
   278       <p>
   279         A <a>valid service type</a> provided in the <code>type</code> attribute of the <a href=
   280         "#dom-navigator-getnetworkservices"><code>getNetworkServices()</code></a> method will be matched against the
   281         services currently contained in the <a>list of available service records</a> according to the algorithms
   282         defined in this specification.
   283       </p>
   284       <p>
   285         A <dfn>user-agent generated callback url</dfn> is a Local-network accessible URL endpoint that a <a>user
   286         agent</a> generates and maintains for receiving HTTP NOTIFY requests from UPnP Event sources. It is only
   287         required when the user agent implements UPnP Service Discovery as defined in this specification.
   288       </p>
   289     </section>
   290     <section>
   291       <h2>
   292         Requesting networked services
   293       </h2>
   294       <pre class="widl">
   295 [Supplemental, NoInterfaceObject]
   296 interface <dfn id="navigatornetworkservice">NavigatorNetworkService</dfn> {
   297   // Obtain a Local-networked Service
   298   void <a href="#dom-navigator-getnetworkservices">getNetworkServices</a>( in any type,
   299                            in <a href=
   300 "#navigatornetworkservicesuccesscallback">NavigatorNetworkServiceSuccessCallback</a> successCallback,
   301                            in optional <a href=
   302 "#navigatornetworkserviceerrorcallback">NavigatorNetworkServiceErrorCallback</a> errorCallback );
   303 };
   304 <a class="externalDFN"
   305      href=
   306      "http://www.whatwg.org/specs/web-apps/current-work/complete/timers.html#navigator">Navigator</a> implements <a href=
   307      "#navigatornetworkservice">NavigatorNetworkService</a>;
   308 
   309 [Callback=FunctionOnly, NoInterfaceObject]
   310 interface <dfn id="navigatornetworkservicesuccesscallback">NavigatorNetworkServiceSuccessCallback</dfn> {
   311   void handleEvent( in <a href="#networkservices">NetworkServices</a> services );
   312 };
   313 
   314 [NoInterfaceObject]
   315 interface <dfn id="navigatornetworkserviceerror">NavigatorNetworkServiceError</dfn> {
   316   const unsigned short <a href="#dom-navigatornetworkserviceerror-permission_denied">PERMISSION_DENIED_ERR</a> = 1;
   317   const unsigned short <a href="#dom-navigatornetworkserviceerror-unknown_type_prefix">UNKNOWN_TYPE_PREFIX_ERR</a> = 2;
   318   readonly attribute unsigned short <a href="#dom-navigatornetworkserviceerror-code">code</a>;
   319 };
   320 
   321 [Callback=FunctionOnly, NoInterfaceObject]
   322 interface <dfn id="navigatornetworkserviceerrorcallback">NavigatorNetworkServiceErrorCallback</dfn> {
   323   void handleEvent( in <a href="#navigatornetworkserviceerror">NavigatorNetworkServiceError</a> error );
   324 };
   325 </pre>
   326       <section>
   327         <h2>
   328           Methods
   329         </h2>
   330         <dl class="domintro">
   331           <dt>
   332             <var title="">window</var> . <code title="dom-navigator"><a href=
   333             "http://www.whatwg.org/specs/web-apps/current-work/complete/timers.html#navigator">navigator</a></code> .
   334             <code title="dom-navigator-getNetworkServices"><a href=
   335             "#dom-navigator-getnetworkservices">getNetworkServices</a></code> ( <var title="">type</var> , <var title=
   336             "">successCallback</var> [, <var title="">errorCallback</var> ] )
   337           </dt>
   338           <dd>
   339             <p>
   340               Prompts the user to select one or more discovered network services that have advertised support for the
   341               requested service type.
   342             </p>
   343             <p>
   344               The <var title="">type</var> argument contains one or more <a>valid service type</a> tokens that the web
   345               page would like to interact with.
   346             </p>
   347             <p>
   348               If the user accepts, the <var title="">successCallback</var> is invoked, with one or more <a href=
   349               "#networkservice"><code>NetworkService</code></a> objects as its argument.
   350             </p>
   351             <p>
   352               If the user declines, the <var title="">errorCallback</var> (if any) is invoked.
   353             </p>
   354           </dd>
   355         </dl>
   356         <div>
   357           <p>
   358             When the <dfn id="dom-navigator-getnetworkservices"
   359                title="dom-navigator-getnetworkservices"><code>getNetworkServices(type, successCallback[,
   360                errorCallback])</code></dfn> method is called, the <a>user agent</a> MUST run the
   361                following steps:
   362           </p>
   363           <ol class="rule">
   364             <li>Let <var>requested control types</var> be initially set to an empty array.
   365             </li>
   366             <li>If <var>type</var> is an array consisting of one or more <a>valid service type</a> tokens, then let
   367             <var>requested control types</var> by the value of <var>type</var>, removing any non-<a>valid service
   368             type</a> tokens from the resulting array.
   369             </li>
   370             <li>If <var>type</var> is a string consisting of one <a>valid service type</a> token, then let
   371             <var>requested control types</var> be an array containing one item with a value of <var>type</var>.
   372             </li>
   373             <li>If <var>requested control types</var> is an array that contains at least one or more <a title=
   374             "valid service type">valid service type</a> tokens then continue to the step labeled <em>process</em>
   375             below. Otherwise, the <a>user agent</a> MUST <a href=
   376             "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
   377                   class="externalDFN">queue a task</a> to invoke <var>errorCallback</var>, if it is provided and is an
   378                   object of type <code>Function</code>, with a new <a href=
   379                   "#navigatornetworkserviceerror"><code>NavigatorNetworkServiceError</code></a> object whose <a href=
   380                   "#dom-navigatornetworkserviceerror-code"><code>code</code></a> attribute has the numeric value 2
   381                   (<a href=
   382                   "#dom-navigatornetworkserviceerror-unknown_type_prefix"><code>UNKNOWN_TYPE_PREFIX_ERR</code></a>) as
   383                   its argument, abort any remaining steps and return.
   384             </li>
   385             <li>
   386               <em>Process</em>: Let <var>services found</var> be an empty array.
   387             </li>
   388             <li>For each <var>available service</var> in the <a>list of available service records</a> run the following
   389             steps:
   390               <ol class="rule">
   391                 <li>For each <var>requested control type</var> in <var>requested control types</var>: If <var>available
   392                 service</var>'s <code>type</code> attribute equals the <var>requested control type</var> then let <var>
   393                   matched service</var> equal the value of <var>available service</var> and continue at the step
   394                   labeled <var>attach</var> below.
   395                 </li>
   396                 <li>Continue at the next <var>available service</var>.
   397                 </li>
   398                 <li>
   399                   <em>Attach</em>: If <var>matched service</var> is not empty then run the following steps:
   400                   <ol class="rule">
   401                     <li>Let <var>new service object</var> be a new <a href=
   402                     "#networkservice"><code>NetworkService</code></a> object, mapping the parameters of <var>matched
   403                     service</var> to this new object where possible.
   404                     </li>
   405                     <li>Append <var>new service object</var> to the <var>services found</var> array.
   406                     </li>
   407                   </ol>
   408                 </li>
   409               </ol>
   410             </li>
   411             <li>If <var>services found</var> is an empty array, then the <a>user agent</a> MUST
   412             <a href="http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
   413                   class="externalDFN">queue a task</a> to invoke <var>errorCallback</var>, if it is provided and is an
   414                   object of type <code>Function</code>, with a new <a href=
   415                   "#navigatornetworkserviceerror"><code>NavigatorNetworkServiceError</code></a> object whose <a href=
   416                   "#dom-navigatornetworkserviceerror-code"><code>code</code></a> attribute has the numeric value 1
   417                   (<a href=
   418                   "#dom-navigatornetworkserviceerror-permission_denied"><code>PERMISSION_DENIED_ERR</code></a>) as its
   419                   argument, abort any remaining steps and return.
   420             </li>
   421             <li>Return, and run the remaining steps asynchronously.
   422             </li>
   423             <li>Optionally, e.g. based on a previously-established user preference, for security reasons, or due to
   424             platform limitations, the <a>user agent</a> MAY <a href=
   425             "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
   426                   class="externalDFN">queue a task</a> to invoke <var>errorCallback</var>, if it is provided and is an
   427                   object of type <code>Function</code>, with a new <a href=
   428                   "#navigatornetworkserviceerror"><code>NavigatorNetworkServiceError</code></a> object whose <a href=
   429                   "#dom-navigatornetworkserviceerror-code"><code>code</code></a> attribute has the numeric value 1
   430                   (<a href=
   431                   "#dom-navigatornetworkserviceerror-permission_denied"><code>PERMISSION_DENIED_ERR</code></a>) as its
   432                   argument, abort any remaining steps and return.
   433             </li>
   434             <li>The <a>user agent</a> MUST prompt the user in a user-agent-specific manner for
   435             permission to provide the <a href=
   436             "http://www.whatwg.org/specs/web-apps/current-work/complete/browsers.html#entry-script"
   437                   class="externalDFN">entry script</a>'s <a href=
   438                   "http://www.whatwg.org/specs/web-apps/current-work/complete/origin-0.html#origin"
   439                   class="externalDFN">origin</a> with an array of <a href=
   440                   "#networkservice"><code>NetworkService</code></a> objects representing the user-authorized subset of
   441                   <var>services found</var>.
   442               <p>
   443                 If the user grants permission to access one or more networked services then the <a>user agent</a>
   444                 SHOULD include an "ongoing local-network communication" indicator.
   445               </p>
   446               <p>
   447                 If the user denies permission, then the <a>user agent</a> MUST <a href=
   448                 "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
   449                    class="externalDFN">queue a task</a> to invoke <var>errorCallback</var>, if it is provided and is an
   450                    object of type <code>Function</code>, with a new <a href=
   451                    "#navigatornetworkserviceerror"><code>NavigatorNetworkServiceError</code></a> object whose <a href=
   452                    "#dom-navigatornetworkserviceerror-code"><code>code</code></a> attribute has the numeric value 1
   453                    (<a href=
   454                    "#dom-navigatornetworkserviceerror-permission_denied"><code>PERMISSION_DENIED_ERR</code></a>) as its
   455                    argument, abort any remaining steps and return.
   456               </p>
   457               <p>
   458                 If the user never responds, this algorithm stalls on this step.
   459               </p>
   460             </li>
   461             <li>Let <var>services</var> be the array of one or more <a href=
   462             "#networkservice"><code>NetworkService</code></a> objects for which the user granted permission.
   463             </li>
   464             <li>For each Object <var>service</var> in <var>services</var>, run the following sub-steps:
   465               <ol class="rule">
   466                 <li>Add the <var>service</var>'s <code>url</code> parameter to the <a>entry script origin's
   467                   <abbr title="Uniform Resource Locator">URL</abbr> whitelist</a>.
   468                 </li>
   469                 <li>If <var>service</var>'s <code>type</code> parameter begins with the DOMString "<code>upnp:</code>"
   470                 and the <var>service</var>'s <code>eventsUrl</code> parameter is not empty then <a>setup a UPnP Events
   471                 Subscription</a> for <var>service</var>.
   472                 </li>
   473               </ol>
   474             </li>
   475             <li>Let <var>services manager</var> be a new <a href="#networkservices"><code>NetworkServices</code></a>
   476             object.
   477             </li>
   478             <li>Set <var>services manager</var>'s <a href=
   479             "#dom-networkservices-servicesavailable"><code>servicesAvailable</code></a> attribute to the number of
   480             services currently found in the <a>list of available service records</a> whose <code>type</code> property
   481             matches any of the tokens requested in <var>requested control types</var>.
   482             </li>
   483             <li>Add the set of <var>services</var> to the <a>list of authorized service records</a> internally against
   484             the newly created <var>services manager</var> object.
   485             </li>
   486             <li>The <a>user agent</a> MUST <a href=
   487             "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
   488                   class="externalDFN">queue a task</a> to invoke <var>successCallback</var> with <var>services
   489                   manager</var> as its argument.
   490             </li>
   491           </ol>
   492           <p>
   493             The <a href="http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#task-source"
   494                class="externalDFN">task source</a> for these <a href=
   495                "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#concept-task"
   496                class="externalDFN">tasks</a> is the <a href=
   497                "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#user-interaction-task-source"
   498                class="externalDFN">user interaction task source</a>.
   499           </p>
   500           <p>
   501             When a <a href="#networkservice"><code>NetworkService</code></a> object is provided to a Web page, the
   502             <a>user agent</a> MUST add the <code>url</code> property to the <dfn>entry script
   503             origin's URL whitelist</dfn>. This list enables the Web page to override and initiate cross-site resource
   504             requests towards these URLs, and any sub-resources of these URLs, within the current <a href=
   505             "http://www.whatwg.org/specs/web-apps/current-work/complete/browsers.html#entry-script"
   506                class="externalDFN">entry script</a>'s <a href=
   507                "http://www.whatwg.org/specs/web-apps/current-work/complete/origin-0.html#origin"
   508                class="externalDFN">origin</a> via various existing mechanisms (e.g. Web Sockets, Server-Sent Events,
   509                Web Messaging, XMLHttpRequest).
   510           </p>
   511           <p>
   512             If the user navigates away from the current browsing context, the <a>user agent</a> <em class=
   513             "ct">MUST</em> remove all previously whitelisted urls from the <a>entry script origin's URL whitelist</a>.
   514             There is no persistence to network service selections provided to a web page. It is not possible to access
   515             a previously white-listed networked service without the necessary user authorization in all of the
   516             following cases:
   517           </p>
   518           <ul>
   519             <li>If the current script is reloaded at any point in the same or different window.
   520             </li>
   521             <li>if the current script reinvokes the <a href=
   522             "#dom-navigator-getnetworkservices"><code>getNetworkServices()</code></a> method at any point in its
   523             execution.
   524             </li>
   525             <li>If the user navigates forward or back in their history to reload the current page.
   526             </li>
   527             <li>If a script is running in a different origin.
   528             </li>
   529           </ul>
   530         </div>
   531       </section>
   532       <section>
   533         <h3>
   534           Error Handling
   535         </h3>
   536         <dl class="domintro">
   537           <dt>
   538             <var title="">error</var> . <code title="dom-NavigatorNetworkServiceError-code"><a href=
   539             "#dom-navigatornetworkserviceerror-code">code</a></code>
   540           </dt>
   541           <dd>
   542             <p>
   543               Returns the current error's error code. At the current time, this will be <code>1</code> or
   544               <code>2</code>, for which the corresponding error constants <a href=
   545               "#dom-navigatornetworkserviceerror-permission_denied"><code>PERMISSION_DENIED_ERR</code></a> and <a href=
   546               "#dom-navigatornetworkserviceerror-unknown_type_prefix"><code>UNKNOWN_TYPE_PREFIX_ERR</code></a> are
   547               defined.
   548             </p>
   549           </dd>
   550         </dl>
   551         <p>
   552           The <dfn id="dom-navigatornetworkserviceerror-code"
   553              title="dom-navigatornetworkserviceerror-code"><code>code</code></dfn> attribute of a <a href=
   554              "#navigatornetworkserviceerror"><code>NavigatorNetworkServiceError</code></a> object <em class=
   555              "ct">MUST</em> return the code for the error, which will be one of the following:
   556         </p>
   557         <dl>
   558           <dt>
   559             <dfn id="dom-navigatornetworkserviceerror-permission_denied"
   560                 title="dom-navigatornetworkserviceerror-permission_denied"><code>PERMISSION_DENIED_ERR</code></dfn>
   561                 (numeric value 1)
   562           </dt>
   563           <dd>
   564             The user or user agent denied the page permission to access any services.
   565           </dd>
   566           <dt>
   567             <dfn id="dom-navigatornetworkserviceerror-unknown_type_prefix"
   568                 title="dom-navigatornetworkserviceerror-unknown_type_prefix"><code>UNKNOWN_TYPE_PREFIX_ERR</code></dfn>
   569                 (numeric value 2)
   570           </dt>
   571           <dd>
   572             No <a>valid service type</a> tokens were provided in the method invocation.
   573           </dd>
   574         </dl>
   575       </section>
   576     </section>
   577     <section>
   578       <h2>
   579         Obtaining networked services
   580       </h2>
   581       <p>
   582         The <a href="#networkservices"><code>NetworkServices</code></a> interface is the top-level response object from
   583         a call to <a href="#dom-navigator-getnetworkservices"><code>getNetworkServices()</code></a> and provides access
   584         to a set of user-authorized <a href="#networkservice"><code>NetworkService</code></a> objects for the given
   585         request.
   586       </p>
   587       <pre class="widl">
   588 [NoInterfaceObject]
   589 interface <dfn id="networkservices">NetworkServices</dfn> {
   590   readonly attribute unsigned long    <a href="#dom-networkservices-length">length</a>;
   591   getter <a href="#networkservice">NetworkService</a> (unsigned long index);
   592   <a href="#networkservice">NetworkService</a>? <a href=
   593 "#dom-networkservices-getservicebyid">getServiceById</a>(DOMString id);
   594 
   595   readonly attribute unsigned long    <a href="#dom-networkservices-servicesavailable">servicesAvailable</a>;
   596 
   597   // event handler attributes
   598            attribute <a href="http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#eventhandler"
   599      class="externalDFN">EventHandler</a>     <a href="#dom-networkservices-onserviceavailable">onserviceavailable</a>;
   600            attribute <a href="http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#eventhandler"
   601      class="externalDFN">EventHandler</a>     <a href=
   602      "#dom-networkservices-onserviceunavailable">onserviceunavailable</a>;
   603 
   604 };
   605 
   606 <a href="#networkservices">NetworkServices</a> implements <a href=
   607 "http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#interface-eventtarget"
   608      class="externalDFN">EventTarget</a>;
   609 </pre>
   610       <section>
   611         <h2>
   612           Attributes
   613         </h2>
   614         <dl class="domintro">
   615           <dt>
   616             <code title="dom-networkservices-length"><a href="#dom-networkservices-length">length</a></code>
   617           </dt>
   618           <dd>
   619             <p>
   620               Returns the current number of services belonging in the respective object's <a>list of authorized service
   621               records</a>.
   622             </p>
   623           </dd>
   624           <dt>
   625             <code title="dom-networkservices-servicesavailable"><a href=
   626             "#dom-networkservices-servicesavailable">servicesAvailable</a></code>
   627           </dt>
   628           <dd>
   629             <p>
   630               Returns the current number of services matching one of the app-requested <a>valid service type</a> tokens
   631               in the <a>list of available service records</a>.
   632             </p>
   633           </dd>
   634         </dl>
   635         <div>
   636           <p>
   637             The <dfn id="dom-networkservices-length"><code>length</code></dfn> attribute MUST
   638             return the number of services represented in the object's corresponding <a>list of authorized service
   639             records</a> at the time of getting.
   640           </p>
   641           <p>
   642             The <dfn id="dom-networkservices-servicesavailable"><code>servicesAvailable</code></dfn> attribute
   643             MUST return the number of services in the <a>list of available service records</a>
   644             whose <code>type</code> attribute matches any of the <a>valid service type</a> tokens that was initially
   645             used to create the current <a href="#networkservices"><code>NetworkServices</code></a> object.
   646           </p>
   647         </div>
   648       </section>
   649       <section>
   650         <h2>
   651           Methods
   652         </h2>
   653         <dl class="domintro">
   654           <dt>
   655             <code title="networkservices-getter"><a href="#networkservices">services</a></code> [ <var title=
   656             "">index</var> ]
   657           </dt>
   658           <dd>
   659             <p>
   660               Returns the specified <a href="#networkservice"><code>NetworkService</code></a> object.
   661             </p>
   662           </dd>
   663           <dt>
   664             <code title="networkservices-getter"><a href="#networkservices">services</a></code> . <code title=
   665             "dom-networkservices-getservicebyid"><a href=
   666             "#dom-networkservices-getservicebyid">getServiceById</a></code> ( <var title="">id</var> )
   667           </dt>
   668           <dd>
   669             <p>
   670               Returns the <a href="#networkservice"><code>NetworkService</code></a> object with the given identifier,
   671               or null if no service has that identifier.
   672             </p>
   673           </dd>
   674         </dl>
   675         <p>
   676           A <a href="#networkservices"><code>NetworkServices</code></a> object represents the current list of one or
   677           more current authorized services - the <a>list of authorized service records</a>. Each item in the <a>list of
   678           authorized service records</a> is represented by a <a href="#networkservice"><code>NetworkService</code></a>
   679           object. The <a>list of authorized service records</a> is <span>immutable</span> meaning that it cannot be
   680           modified for the lifetime of a <a href="#networkservices"><code>NetworkServices</code></a> object.
   681         </p>
   682         <p class="note">
   683           Each service in a <a href="#networkservices"><code>NetworkServices</code></a> object thus has an index; the
   684           first has the index 0, and each subsequent service is numbered one higher than the previous one.
   685         </p>
   686         <p>
   687           The <a href=
   688           "http://www.whatwg.org/specs/web-apps/current-work/multipage/infrastructure.html#supported-property-indices"
   689              class="externalDFN">supported property indices</a> of <a href=
   690              "#networkservices"><code>NetworkServices</code></a> objects at any instant are the numbers from zero to
   691              the number of items in the <a>list of authorized service records</a> represented by the respective object
   692              minus one, if any services are represented in the <a>list of authorized service records</a>.
   693         </p>
   694         <p>
   695           To <a href=
   696           "http://www.whatwg.org/specs/web-apps/current-work/multipage/infrastructure.html#determine-the-value-of-an-indexed-property"
   697              class="externalDFN">determine the value of an indexed property</a> for a given index <var>index</var> in a
   698              <a href="#networkservices"><code>NetworkServices</code></a> object's <a>list of authorized service
   699              records</a>, the user agent MUST return the <a href=
   700              "#networkservice"><code>NetworkService</code></a> object that represents the <var>index</var>th service in
   701              the <a>list of authorized service records</a>.
   702         </p>
   703         <p>
   704           The <dfn id="dom-networkservices-getservicebyid"><code>getServiceById(id)</code></dfn> method <em class=
   705           "ct">MUST</em> return the first <a href="#networkservice"><code>NetworkService</code></a> object in the
   706           <a>list of authorized service records</a> represented by the respective object whose <a href=
   707           "#dom-networkservice-id"><code>id</code></a> attribute is equal to the value of the <var>id</var> argument.
   708           When no services in the <a>list of authorized service records</a> match the given argument, the method
   709           MUST return null.
   710         </p>
   711         <p>
   712           Services available within the local network can connect and disconnect at different times during the
   713           execution of a web page. A <a>user agent</a> can inform a web page when the state of networked services
   714           matching the requested <a>valid service type</a> change. Web pages can use this information to enable in-page
   715           experiences for communicating the state of networked services with the ability to change the particular
   716           service or set of services the page is connected to by re-invoking the <a href=
   717           "#dom-navigator-getnetworkservices"><code>getNetworkServices()</code></a> method.
   718         </p>
   719       </section>
   720       <section>
   721         <h2>
   722           Events
   723         </h2>
   724         <p>
   725           The following are the event handlers (and their corresponding event handler event types) that <em class=
   726           "ct">MUST</em> be supported, as IDL attributes, by all objects implementing the <a href=
   727           "#networkservices"><code>NetworkServices</code></a> interface:
   728         </p>
   729         <table border="1">
   730           <thead>
   731             <tr>
   732               <th>
   733                 <span title="event handlers">Event handler</span>
   734               </th>
   735               <th>
   736                 <span>Event handler event type</span>
   737               </th>
   738             </tr>
   739           </thead>
   740           <tbody>
   741             <tr>
   742               <td>
   743                 <dfn id="dom-networkservices-onserviceavailable"
   744                     title="dom-NetworkServices-onserviceavailable"><code>onserviceavailable</code></dfn>
   745               </td>
   746               <td>
   747                 <a href="#event-serviceavailable"><code>serviceavailable</code></a>
   748               </td>
   749             </tr>
   750             <tr>
   751               <td>
   752                 <dfn id="dom-networkservices-onserviceunavailable"
   753                     title="dom-NetworkServices-onserviceunavailable"><code>onserviceunavailable</code></dfn>
   754               </td>
   755               <td>
   756                 <a href="#event-serviceunavailable"><code>serviceunavailable</code></a>
   757               </td>
   758             </tr>
   759           </tbody>
   760         </table>
   761       </section>
   762     </section>
   763     <section>
   764       <h2>
   765         Communicating with a networked service
   766       </h2>
   767       <p>
   768         The <a href="#networkservice"><code>NetworkService</code></a> interface is used to provide a set of connection
   769         information for an HTTP service endpoint and if available, service events, running on a networked device.
   770       </p>
   771       <pre class="widl">
   772 [NoInterfaceObject]
   773 interface <dfn id="networkservice">NetworkService</dfn> {
   774   readonly attribute DOMString        <a href="#dom-networkservice-id">id</a>;
   775   readonly attribute DOMString        <a href="#dom-networkservice-name">name</a>;
   776   readonly attribute DOMString        <a href="#dom-networkservice-type">type</a>;
   777   readonly attribute DOMString        <a href="#dom-networkservice-url">url</a>;
   778   readonly attribute DOMString        <a href="#dom-networkservice-config">config</a>;
   779 
   780   readonly attribute boolean          <a href="#dom-networkservice-online">online</a>;
   781 
   782   // event handler attributes
   783            attribute <a href="http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#eventhandler"
   784      class="externalDFN">EventHandler</a>     <a href="#dom-networkservice-onserviceonline">onserviceonline</a>;
   785            attribute <a href="http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#eventhandler"
   786      class="externalDFN">EventHandler</a>     <a href="#dom-networkservice-onserviceoffline">onserviceoffline</a>;
   787 
   788            attribute <a href="http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html#eventhandler"
   789      class="externalDFN">EventHandler</a>     <a href="#dom-networkservice-onnotify">onnotify</a>;
   790 };
   791 
   792 <a href="#networkservice">NetworkService</a> implements <a href=
   793 "http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#interface-eventtarget"
   794      class="externalDFN">EventTarget</a>;
   795 </pre>
   796       <section>
   797         <h2>
   798           Attributes
   799         </h2>
   800         <dl class="domintro">
   801           <dt>
   802             <var title="">service</var> . <code title="dom-networkservice-id"><a href=
   803             "#dom-networkservice-id">id</a></code>
   804           </dt>
   805           <dd>
   806             <p>
   807               A unique identifier for the given user-selected service instance.
   808             </p>
   809           </dd>
   810           <dt>
   811             <var title="">service</var> . <code title="dom-networkservice-name"><a href=
   812             "#dom-networkservice-name">name</a></code>
   813           </dt>
   814           <dd>
   815             <p>
   816               The name of the user-selected service.
   817             </p>
   818           </dd>
   819           <dt>
   820             <var title="">service</var> . <code title="dom-networkservice-type"><a href=
   821             "#dom-networkservice-type">type</a></code>
   822           </dt>
   823           <dd>
   824             <p>
   825               The <a>valid service type</a> token value of the user-selected service.
   826             </p>
   827           </dd>
   828           <dt>
   829             <var title="">service</var> . <code title="dom-networkservice-url"><a href=
   830             "#dom-networkservice-url">url</a></code>
   831           </dt>
   832           <dd>
   833             <p>
   834               The control URL endpoint (including any required port information) of the user-selected control service
   835               that has been added to the <a>entry script origin's URL whitelist</a>.
   836             </p>
   837           </dd>
   838           <dt>
   839             <var title="">service</var> . <code title="dom-networkservice-config"><a href=
   840             "#dom-networkservice-config">config</a></code>
   841           </dt>
   842           <dd>
   843             <p>
   844               The configuration information associated with the service depending on the requested service type.
   845             </p>
   846           </dd>
   847         </dl>
   848         <p>
   849           The <dfn id="dom-networkservice-id"><code>id</code></dfn> attribute is a unique identifier for the service.
   850           The same service provided at different times or on different objects MUST have the same
   851           <a href="#dom-networkservice-id"><code>id</code></a> value.
   852         </p>
   853         <p>
   854           The <dfn id="dom-networkservice-name"><code>name</code></dfn> attribute represents a human-readable title for
   855           the service.
   856         </p>
   857         <p>
   858           The <dfn id="dom-networkservice-type"><code>type</code></dfn> attribute reflects the value of the <a>valid
   859           service type</a> of the service.
   860         </p>
   861         <p>
   862           The <dfn id="dom-networkservice-url"><code>url</code></dfn> attribute is an <a href=
   863           "http://www.w3.org/TR/html5/urls.html#absolute-url"
   864              class="externalDFN">absolute URL</a> pointing to the root HTTP endpoint for the service that has been
   865              added to the <a>entry script origin's URL whitelist</a>. Web pages can subsequently use this value for
   866              implicit cross-document messaging via various existing mechanisms (e.g. Web Sockets, Server-Sent Events,
   867              Web Messaging, XMLHttpRequest).
   868         </p>
   869         <p>
   870           The <dfn id="dom-networkservice-config"><code>config</code></dfn> attribute provides the raw configuration
   871           information extracted from the given network service.
   872         </p>
   873       </section>
   874       <section>
   875         <h3>
   876           States
   877         </h3>
   878         <dl class="domintro">
   879           <dt>
   880             <var title="">service</var> . <code title="dom-networkservice-online"><a href=
   881             "#dom-networkservice-online">online</a></code>
   882           </dt>
   883           <dd>
   884             <p>
   885               Returns <code>true</code> if the service is reporting that it is accessible on the local network or
   886               <code>false</code> if the service is reporting that it is no longer accessible (temporarily or
   887               permanently) on the local network.
   888             </p>
   889           </dd>
   890         </dl>
   891         <p>
   892           The <dfn id="dom-networkservice-online"><code>online</code></dfn> attribute indicates whether the service is
   893           reporting itself as being either <var>online</var>, and therefore accessible on the local network, in which
   894           case this attribute will return <code>true</code> or, <var>offline</var>, and therefore not accessible on the
   895           local network, either temporarily or permanently, in which case this attribute will return
   896           <code>false</code>. This attribute MUST default to <code>true</code>.
   897         </p>
   898       </section>
   899       <section>
   900         <h3>
   901           Events
   902         </h3>
   903         <p>
   904           The following are the event handlers (and their corresponding event handler event types) that <em class=
   905           "ct">MUST</em> be supported, as IDL attributes, by all objects implementing the <a href=
   906           "#networkservice"><code>NetworkService</code></a> interface:
   907         </p>
   908         <table border="1">
   909           <thead>
   910             <tr>
   911               <th>
   912                 <span title="event handlers">Event handler</span>
   913               </th>
   914               <th>
   915                 <span>Event handler event type</span>
   916               </th>
   917             </tr>
   918           </thead>
   919           <tbody>
   920             <tr>
   921               <td>
   922                 <dfn id="dom-networkservice-onnotify"
   923                     title="dom-NetworkService-onnotify"><code>onnotify</code></dfn>
   924               </td>
   925               <td>
   926                 <a href="#event-notify"><code>notify</code></a>
   927               </td>
   928             </tr>
   929             <tr>
   930               <td>
   931                 <dfn id="dom-networkservice-onserviceonline"
   932                     title="dom-NetworkService-onserviceonline"><code>onserviceonline</code></dfn>
   933               </td>
   934               <td>
   935                 <a href="#event-serviceonline"><code>serviceonline</code></a>
   936               </td>
   937             </tr>
   938             <tr>
   939               <td>
   940                 <dfn id="dom-networkservice-onserviceoffline"
   941                     title="dom-NetworkService-onserviceoffline"><code>onserviceoffline</code></dfn>
   942               </td>
   943               <td>
   944                 <a href="#event-serviceoffline"><code>serviceoffline</code></a>
   945               </td>
   946             </tr>
   947           </tbody>
   948         </table>
   949       </section>
   950     </section>
   951     <section>
   952       <h2>
   953         Service Discovery
   954       </h2>
   955       <p>
   956         A <a>user agent</a> conforming to this specification MAY implement <abbr title=
   957         "Simple Service Discovery Protocol">SSDP</abbr> [[!UPNP-DEVICEARCH11]] and Zeroconf [[!DNS-SD]] + [[!MDNS]]
   958         service discovery mechanisms to enable Web pages to request and connect with HTTP services running on networked
   959         devices, discovered via either mechanism, through this API. When a <a>user agent</a> implements either of these
   960         service discovery mechanisms, then it MUST conform to the corresponding algorithms provided
   961         in this section of the specification.
   962       </p>
   963       <p>
   964         This section presents how the results of these two service discovery mechanisms will be matched to requested
   965         service types, how the user agent stores available and active services, how their properties are applied to any
   966         resulting <a href="#networkservice"><code>NetworkService</code></a> objects.
   967       </p>
   968       <p>
   969         It is expected that user agents will perform these service discovery mechanisms asynchronously and
   970         periodically update the <a>list of networked devices</a> as required. The timing of any service discovery
   971         mechanisms is an implementation detail left to the discretion of the implementer (e.g. once on user agent
   972         start-up, every X seconds during user agent execution or on invocation of this API from a Web page).
   973       </p>
   974       <p>
   975         The <dfn>list of available service records</dfn> is a single dynamic internal lookup table within user agents
   976         that is used to track all the services that have been discovered and are available in the current network at
   977         any given time. At any point during the running of either of the two service discovery mechanisms then existing
   978         entries within this table can be updated, entries can be added and entries can be removed as the status of
   979         networked services changes according to the rules defined in this specification.
   980       </p>
   981       <p>
   982         The <dfn>list of authorized service records</dfn> is a single dynamic internal lookup table within user agents
   983         that is used to track the current services that are being shared with web pages at any given time from the
   984         <a>list of available service records</a>. Each record in the <a>list of authorized service records</a> is
   985         associated with a <var>services manager</var> object that is assigned as part of the <a href=
   986         "#dom-navigator-getnetworkservices"><code>getNetworkServices()</code></a> algorithm.
   987       </p>
   988       <p>
   989         The rule for <dfn>adding an available service</dfn> is the process of adding a new service or updating an
   990         existing service in the <a>list of available service records</a> that is generally available on the user's
   991         current network. This rule takes one argument, <var>network service record</var>, and consists of running the
   992         following steps:
   993       </p>
   994       <ol class="rule">
   995         <li>Let <var>new service registration flag</var> be <code>true</code>.
   996         </li>
   997         <li>For each <var>existing service record</var> in the current <a>list of available service records</a>, run
   998         the following sub-steps:
   999           <ol class="rule">
  1000             <li>If the <var>existing service record</var>'s <code>id</code> property does not equal <var>network
  1001             service record</var>'s <code>id</code> property then abort any remaining sub-steps and continue at the next
  1002             available <var>existing service record</var>.
  1003             </li>
  1004             <li>Set <var>new service registration flag</var> to <code>false</code>.
  1005             </li>
  1006             <li>Replace the value of <var>existing service record</var> in the current <a>list of available service
  1007             records</a> with the value of <var>network service record</var>.
  1008             </li>
  1009           </ol>
  1010         </li>
  1011         <li>If <var>new service registration flag</var> is set to <code>true</code> then add <var>network service
  1012         record</var> to the <a>list of available service records</a> as a new entry.
  1013         </li>
  1014         <li>For each <var>active service</var> in the <a>list of authorized service records</a> run the following
  1015         steps:
  1016           <ol class="rule">
  1017             <li>If <var>network service record</var>'s <code>type</code> property does not equal the current
  1018             <var>active service</var>'s <code>type</code> attribute then abort any remaining sub-steps for this
  1019             <var>active service</var> and continue at the next available <var>active service</var>.
  1020             </li>
  1021             <li>If the <var>new service registration flag</var> is set to <code>true</code> then increment the
  1022               <a href="#dom-networkservices-servicesavailable"><code>servicesAvailable</code></a> attribute of the
  1023               <var>services manager</var> associated with the current <var>active service</var> object by
  1024               <code>1</code> and then <a href=
  1025               "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
  1026                   class="externalDFN">queue a task</a> to dispatch a newly created event with the name <a href=
  1027                   "#event-serviceavailable"><code>serviceavailable</code></a> that uses the <a href=
  1028                   "http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1029                   class="externalDFN"><code>Event</code></a> interface, which does not bubble, is not cancellable, and
  1030                   has no default action, at the <var>services manager</var> associated with the current <var>active
  1031                   service</var> object.
  1032             </li>
  1033             <li>Set <var>active service</var>'s <a href="#dom-networkservice-online"><code>online</code></a> attribute
  1034             to <code>true</code> and then <a href=
  1035             "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
  1036                   class="externalDFN">queue a task</a> to dispatch a newly created event with the name <a href=
  1037                   "#event-serviceonline"><code>serviceonline</code></a> that uses the <a href=
  1038                   "http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1039                   class="externalDFN"><code>Event</code></a> interface, which does not bubble, is not cancellable, and
  1040                   has no default action, at the current <var>active service</var> object.
  1041             </li>
  1042           </ol>
  1043         </li>
  1044       </ol>
  1045       <p>
  1046         The rule for <dfn>removing an available service</dfn> is the general process of removing a service from the
  1047         <a>list of available service records</a> that has left the user's current network or has otherwise expired.
  1048         This rule takes one argument, <var>service identifier</var>, and consists of running the following steps:
  1049       </p>
  1050       <ol class="rule">
  1051         <li>For each <var>existing service record</var> in the current <a>list of available service records</a>, run
  1052         the following sub-steps:
  1053           <ol class="rule">
  1054             <li>If the <var>existing service record</var>'s <code>id</code> property does not match <var>service
  1055             identifier</var> then skip any remaining sub-steps for the current <var>existing service record</var> and
  1056             continue at the next available <var>existing service record</var>.
  1057             </li>
  1058             <li>If the <var>existing service record</var>'s <code>type</code> property begins with the DOMString
  1059             "<code>upnp:</code>" and <var>existing service record</var>'s <code>eventsURL</code> property is set then
  1060             run the rule to <a>terminate an existing UPnP Events Subscription</a>, if one is currently active (as a
  1061             result of having previously called <a>setup a UPnP Events Subscription</a> against the current
  1062             <var>existing service record</var>).
  1063             </li>
  1064             <li>For each <var>active service</var> in <a>list of authorized service records</a> run the following
  1065             steps:
  1066               <ol class="rule">
  1067                 <li>If <var>existing service record</var>'s <code>type</code> property does not equal the current <var>
  1068                   active service</var>'s <code>type</code> attribute then abort any remaining sub-steps for this
  1069                   <var>active service</var> and continue at the next available <var>active service</var>.
  1070                 </li>
  1071                 <li>Decrement the <a href="#dom-networkservices-servicesavailable"><code>servicesAvailable</code></a>
  1072                 attribute of the <var>services manager</var> associated with the current <var>active service</var>
  1073                 object by <code>1</code> and then <a href=
  1074                 "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
  1075                       class="externalDFN">queue a task</a> to dispatch a newly created event with the name <a href=
  1076                       "#event-serviceunavailable"><code>serviceunavailable</code></a> that uses the <a href=
  1077                       "http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1078                       class="externalDFN"><code>Event</code></a> interface, which does not bubble, is not cancellable,
  1079                       and has no default action, at the <var>services manager</var> associated with the current
  1080                       <var>active service</var> object.
  1081                 </li>
  1082                 <li>Set <var>active service</var>'s <a href="#dom-networkservice-online"><code>online</code></a>
  1083                 attribute to <code>false</code> and then <a href=
  1084                 "http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
  1085                       class="externalDFN">queue a task</a> to dispatch a newly created event with the name <a href=
  1086                       "#event-serviceoffline"><code>serviceoffline</code></a> that uses the <a href=
  1087                       "http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1088                       class="externalDFN"><code>Event</code></a> interface, which does not bubble, is not cancellable,
  1089                       and has no default action, at the current <var>active service</var> object.
  1090                 </li>
  1091               </ol>
  1092             </li>
  1093             <li>Remove <var>existing service record</var> from the current <a>list of available service records</a>.
  1094             </li>
  1095           </ol>
  1096         </li>
  1097       </ol>
  1098       <p>
  1099         User agents SHOULD expire a service record from the <a>list of available service
  1100         records</a> when its <code>expiryTimestamp</code> attribute exceeds the current UTC timestamp. When this
  1101         condition is met the <a>user agent</a> SHOULD run the rule for <a>removing an available service</a>, passing in
  1102         the expired service record's <code>id</code> attribute as the only argument.
  1103       </p>
  1104       <section>
  1105         <h4>
  1106           Zeroconf (<abbr title="Multicast DNS">mDNS</abbr> + <abbr title="Domain Name System">DNS</abbr>-<abbr title=
  1107           "Service Discovery">SD</abbr>)
  1108         </h4>
  1109         <p>
  1110           For each DNS response received from a user-agent-initiated Multicast DNS Browse for <abbr title=
  1111           "DNS Pointer Record">PTR</abbr> records with the name <code>_services._dns-sd._udp</code> on the resolved
  1112           recommended automatic browsing domain [[!MDNS]], the <a>user agent</a> MUST run the
  1113           following steps:
  1114         </p>
  1115         <ol class="rule">
  1116           <li>Let <var>service mDNS responses</var> be an array of PTR records received by issuing a Multicast DNS
  1117           Browse for PTR records with the name of the current discovered service type.
  1118           </li>
  1119           <li>For each Object <var>service mDNS response</var> in <var>service mDNS responses</var>, run the following
  1120           steps:
  1121             <ol>
  1122               <li>Let <var>network service record</var> be an Object consisting of the following empty properties:
  1123               <code>id</code>, <code>name</code>, <code>type</code>, <code>url</code>, <code>config</code>,
  1124               <code>expiryTimestamp</code>.
  1125               </li>
  1126               <li>Set <var>network service record</var>'s <code>id</code> property to the value of the full PTR Service
  1127               Instance Name [[!MDNS]].
  1128               </li>
  1129               <li>Set <var>network service record</var>'s <code>name</code> property to the value of the PTR Service
  1130               Instance Name's <var>Instance</var> component [[!MDNS]].
  1131               </li>
  1132               <li>Set <var>network service record</var>'s <code>type</code> property to the concatenation of the string
  1133               <code>zeroconf:</code> followed be the value of the PTR Service Instance Name's <var>Service</var>
  1134               component [[!MDNS]].
  1135               </li>
  1136               <li>Set <var>network service record</var>'s <code>url</code> property to the resolvable Service URL
  1137               obtained from performing an DNS-SD Lookup [[!DNS-SD]] of the current service from the PTR record provided
  1138               [[!MDNS]].
  1139               </li>
  1140               <li>Set <var>network service record</var>'s <code>config</code> property to the string value of the
  1141               contents of the first DNS-SD TXT record associated with the <var>service mDNS response</var> as defined
  1142               in [[!DNS-SD]].
  1143               </li>
  1144               <li>Set <var>network service record</var>'s <code>expiryTimestamp</code> property to the value of the
  1145               current date, in UTC timestamp format, plus a value of <code>120</code> seconds.
  1146               </li>
  1147               <li>Run the general rule for <a>adding an available service</a>, passing in the current <var>network
  1148               service record</var> as the only argument.
  1149               </li>
  1150             </ol>
  1151           </li>
  1152         </ol>
  1153       </section>
  1154       <section>
  1155         <h5>
  1156           Simple Service Discovery Protocol (<abbr title="Simple Service Discovery Protocol">SSDP</abbr>)
  1157         </h5>
  1158         <p>
  1159           A user agent that implements UPnP service discovery MUST issue an <dfn>advertisement for
  1160           UPnP root devices</dfn> against the user's current local network according to the full normative text and
  1161           timing provided in 'Section 1.3.2: Search request with M-SEARCH' detailed in [[!UPNP-DEVICEARCH11]].
  1162         </p>
  1163         <p>
  1164           The user agent MUST issue all <a title=
  1165           "advertisement for UPnP root devices">advertisements for UPnP root devices</a> with a HTTP request line equal
  1166           to <code>M-SEARCH * HTTP/1.1</code>, with a HOST header equal to the reserved multicast address and port of
  1167           <code>239.255.255.250:1900</code>, a MAN header equal to <code>ssdp:discover</code>, an ST header equal to
  1168           <code>upnp:rootdevice</code> and a user-agent defined MX header equal to a <dfn>maximum UPnP advertisement
  1169           response wait time</dfn> value between <code>1</code> and <code>5</code> seconds.
  1170         </p>
  1171         <p>
  1172           The user agent MUST listen for incoming requests and process any incoming responses to
  1173           any <a>advertisement for UPnP root devices</a> on the <dfn>standard UPnP address and port</dfn>, on all
  1174           current local network interface addresses with the port <code>1900</code>, according to the rules defined in
  1175           this section.
  1176         </p>
  1177         <p>
  1178           For each <dfn>HTTP Response</dfn> following an initial <a>advertisement for UPnP root devices</a> sent on a
  1179           <a>standard UPnP address and port</a> the user agent MUST run the following steps:
  1180         </p>
  1181         <ol class="rule">
  1182           <li>If the <a>HTTP Response</a> is not a HTTP 200 OK response then this response is invalid and the user
  1183           agent MUST discard this response, abort any remaining steps and return. The user agent
  1184           MAY issue a new <a>advertisement for UPnP root devices</a> as a result of this error
  1185           occurring.
  1186           </li>
  1187           <li>If the <a>maximum UPnP advertisement response wait time</a> has been exceeded since the initial
  1188           <a>advertisement for UPnP root devices</a> was sent then the <a>HTTP Response</a> is invalid and the user
  1189           agent MUST discard this response, abort any remaining steps and return.
  1190           </li>
  1191           <li>Let <var>ssdp device</var> be an Object with a property for each HTTP header received in the <a>HTTP
  1192           Response</a>, with each key being the name of a HTTP response header and each value being that HTTP response
  1193           header's value.
  1194           </li>
  1195           <li>If <var>ssdp device</var> does not contain at least one <var>CACHE-CONTROL</var> entry, at least one
  1196           <var>USN</var> entry, at least one <var>ST</var> entry and at least one <var>LOCATION</var> entry or the
  1197           value of its <var>ST</var> entry is not <code>upnp:rootdevice</code>, then the <a>HTTP Response</a> is
  1198           invalid and the <a>user agent</a> MUST discard this response, abort any remaining steps
  1199           and return.
  1200           </li>
  1201           <li>The user agent MUST run the rule for <a>obtaining a UPnP Device Description File</a>
  1202           passing in the first occurrence of <var>LOCATION</var> from <var>ssdp device</var> as the <var>device
  1203           descriptor URL</var> argument and the first occurrence of <var>USN</var> from <var>ssdp device</var> as the
  1204           <var>device identifier</var> argument and the first occurrence of <var>CACHE-CONTROL</var> from <var>ssdp
  1205           device</var> as the <var>device expiry</var> argument.
  1206           </li>
  1207         </ol>
  1208         <p>
  1209           For each <dfn>HTTP Request</dfn> received on a <a>standard UPnP address and port</a> the user agent
  1210           MUST run the following steps:
  1211         </p>
  1212         <ol class="rule">
  1213           <li>If the <a>HTTP Request</a> is not a HTTP NOTIFY request then it is not a valid UPnP Request and the user
  1214           agent MUST return a HTTP 200 OK response, discard this request, abort any remaining steps
  1215           and return.
  1216           </li>
  1217           <li>Let <var>ssdp device</var> be an Object with a property for each HTTP header received in the <a>HTTP
  1218           Request</a>, with each key being the name of a HTTP header and each value being that HTTP header's value.
  1219           </li>
  1220           <li>If <var>ssdp device</var> does not contain at least one <var>CACHE-CONTROL</var> entry, at least one
  1221           <var>USN</var> entry, at least one <var>NT</var> entry, at least one <var>NTS</var> entry and at least one
  1222           <var>LOCATION</var> entry or the value of its <var>NT</var> entry is not <code>upnp:rootdevice</code>, then
  1223           the <a>HTTP Request</a> is a malformed UPnP Request and the <a>user agent</a> MUST return
  1224           a 400 Bad Request response, discard this request, abort any remaining steps and return.
  1225           </li>
  1226           <li>If <var>ssdp device</var>'s <var>NTS</var> entry is equal to <code>ssdp:alive</code> or
  1227           <code>ssdp:update</code> then the user agent MUST run the rule for <a>obtaining a UPnP
  1228           Device Description File</a> passing in the first occurrence of <var>LOCATION</var> from <var>ssdp
  1229           device</var> as the <var>device descriptor URL</var> argument and the first occurrence of <var>USN</var> from
  1230           <var>ssdp device</var> as the <var>device identifier</var> argument and the first occurrence of
  1231           <var>CACHE-CONTROL</var> from <var>ssdp device</var> as the <var>device expiry</var>.<br>
  1232             <br>
  1233             Otherwise, if <var>ssdp device</var>'s <var>NTS</var> entry is equal to <code>ssdp:byebye</code> then the
  1234             user agent MUST run the rule for <a>removing all services from a registered UPnP
  1235             Device</a> passing in the first occurrence of <var>USN</var> from <var>ssdp device</var> as the <var>device
  1236             identifier</var> argument.
  1237           </li>
  1238         </ol>
  1239         <p>
  1240           The rule for <dfn>obtaining a UPnP Device Description File</dfn> is the process of obtaining the contents of
  1241           a standard UPnP Device Description [[!UPNP-DEVICEARCH11]] from a URL-based resource. This rule takes three
  1242           arguments - <var>device descriptor URL</var>, <var>device identifier</var> and <var>device expiry</var> - and
  1243           when called the user agent MUST run the following steps:
  1244         </p>
  1245         <ol class="rule">
  1246           <li>Let <var>device descriptor file</var> contain the contents of the file located at the URL provided in
  1247           <var>device descriptor URL</var> obtained according to the rules defined in 'Section 2.11: Retrieving a
  1248           description using HTTP' in [[!UPNP-DEVICEARCH11]].
  1249           </li>
  1250           <li>If the value provided in <var>device descriptor URL</var> cannot be resolved as a reachable URL on the
  1251           current network or the <var>root device descriptor file</var> remains empty then it is invalid and the
  1252           <a>user agent</a> MUST abort any remaining steps and return.
  1253           </li>
  1254           <li>Run the rule for <a>processing a UPnP Device Description File</a>, passing in the current <var>device
  1255           descriptor file</var>, <var>device identifier</var> and <var>device expiry</var> arguments.
  1256           </li>
  1257           <li>If the current <var>device descriptor file</var> contains a <code>&lt;deviceList&gt;</code> element then
  1258           for each <code>&lt;device&gt;</code> element within <code>&lt;deviceList&gt;</code> - herein known as an
  1259           <var>embedded device descriptor file</var> - the user agent MUST run the rule for
  1260           <a>processing a UPnP Device Description File</a>, passing in the current <var>embedded device descriptor
  1261           file</var> as the <var>device descriptor file</var> argument, along with the common <var>device
  1262           identifier</var> and <var>device expiry</var> arguments.
  1263           </li>
  1264         </ol>
  1265         <p>
  1266           The rule for <dfn>processing a UPnP Device Description File</dfn> is the process of parsing the contents of a
  1267           standard UPnP Device Description [[!UPNP-DEVICEARCH11]] and registering the UPnP services contained therein
  1268           within the <a>list of available service records</a>.
  1269         </p>
  1270         <p>
  1271           The rule for <a>processing a UPnP Device Description File</a> takes three arguments - <var>device descriptor
  1272           file</var>, <var>device identifier</var> and <var>device expiry</var> - and when called the user agent
  1273           MUST run the following steps:
  1274         </p>
  1275         <ol class="rule">
  1276           <li>Let <var>advertised services</var> be a list of all advertised services obtained from the <var>device
  1277           descriptor file</var> containing the value of the first occurrence of the <code>&lt;serviceList&gt;</code>
  1278           element as it is defined in 'Section 2.3: Device Description' in [[!UPNP-DEVICEARCH11]].
  1279           </li>
  1280           <li>For each <code>&lt;service&gt;</code> element - known as an <var>advertised service</var> - in
  1281           <var>advertised services</var> run the following steps:
  1282             <ol class="rule">
  1283               <li>Let <var>network service record</var> be a new Object consisting of the following empty properties:
  1284               <code>id</code>, <code>deviceId</code>, <code>name</code>, <code>type</code>, <code>url</code>,
  1285               <code>eventsUrl</code>, <code>config</code>, <code>expiryTimestamp</code>.
  1286               </li>
  1287               <li>Set <var>network service record</var>'s <code>id</code> property to the concatenated string value of
  1288               <var>device identifier</var> with the <var>advertised service</var>'s <code>&lt;serviceId&gt;</code>
  1289               sub-element.
  1290               </li>
  1291               <li>Set <var>network service record</var>'s <code>deviceId</code> property to the value of <var>device
  1292               identifier</var>.
  1293               </li>
  1294               <li>Set <var>network service record</var>'s <code>name</code> property to the string value of the first
  1295               occurrence of the <var>advertised service</var>'s <code>&lt;serviceId&gt;</code> sub-element.
  1296               </li>
  1297               <li>Set <var>network service record</var>'s <code>type</code> property to the concatenation of the string
  1298               <code>upnp:</code> followed by the string value of the first occurrence of the <var>advertised
  1299               service</var>'s <code>&lt;serviceType&gt;</code> sub-element.
  1300               </li>
  1301               <li>Set <var>network service record</var>'s <code>url</code> property to the string value of the first
  1302               occurrence of the <var>advertised service</var>'s <code>&lt;controlURL&gt;</code> sub-element.
  1303               </li>
  1304               <li>Set <var>network service record</var>'s <code>config</code> property to the string value of the
  1305               contents of the first occurrence of the <code>&lt;device&gt;</code> element in the <var>device descriptor
  1306               file</var>.
  1307               </li>
  1308               <li>If <var>advertised service</var>'s <code>&lt;eventSubURL&gt;</code> sub-element is not empty, then
  1309               set <var>network service record</var>'s <code>eventsUrl</code> property to the string value of the first
  1310               occurrence of the <var>advertised service</var>'s <code>&lt;eventSubURL&gt;</code> sub-element.
  1311               Otherwise, do not set <var>network service record</var>'s <code>eventsUrl</code> property.
  1312               </li>
  1313               <li>Set <var>network service record</var>'s <code>expiryTimestamp</code> property to the value of the
  1314               current date, in UTC timestamp format, plus the value of <var>device expiry</var>.
  1315               </li>
  1316               <li>Run the general rule for <a>adding an available service</a>, passing in the current <var>network
  1317               service record</var> as the only argument.
  1318               </li>
  1319             </ol>
  1320           </li>
  1321         </ol>
  1322         <p>
  1323           The rule for <dfn>removing all services from a registered UPnP Device</dfn> is the process of removing all
  1324           services associated with a device from the <a>list of available service records</a> that has left the user's
  1325           current network or has otherwise timed out or expired. This rule takes one argument, <var>device
  1326           identifier</var>, and consists of running the following steps:
  1327         </p>
  1328         <ol class="rule">
  1329           <li>For each <var>existing service record</var> in the current <a>list of available service records</a>, run
  1330           the following sub-steps:
  1331             <ol class="rule">
  1332               <li>If the <var>existing service record</var>'s <code>deviceId</code> property does not match <var>device
  1333               identifier</var> then skip any remaining sub-steps for the current <var>existing service record</var> and
  1334               continue at the next available <var>existing service record</var>.
  1335               </li>
  1336               <li>Run the general rule for <a>removing an available service</a> passing in <var>existing service
  1337               record</var>'s <code>id</code> property as the only argument.
  1338               </li>
  1339             </ol>
  1340           </li>
  1341         </ol>
  1342         <p>
  1343           When the <a>user agent</a> is to <dfn>setup a UPnP Events Subscription</dfn>, it is to run the following
  1344           steps with the current <var>network service record</var> object as defined in 'Section 4.1.2: SUBSCRIBE with
  1345           NT and CALLBACK' in [[!UPNP-DEVICEARCH11]]:
  1346         </p>
  1347         <ol class="rule">
  1348           <li>If <var>network service record</var>'s <code>eventsUrl</code> property is empty then the <a>user
  1349           agent</a> MUST abort these steps.
  1350           </li>
  1351           <li>Let <var>callback URL</var> be the value of creating a new <a>user-agent generated callback url</a>.
  1352           </li>
  1353           <li>Send a HTTP SUBSCRIBE request with a <em>NT</em> header with a string value of <code>upnp:event</code>, a
  1354           <em>TIMEOUT</em> header with a user-agent defined timeout value (in the form <code>Second-XX</code> where
  1355           <code>XX</code> is the user-agent defined timeout value in seconds) and a <em>CALLBACK</em> header with a
  1356           string value of <var>callback URL</var> towards the <var>network service record</var>'s
  1357           <code>eventsUrl</code> property.
  1358           </li>
  1359           <li>If a non-200 OK response is received from the HTTP SUBSCRIBE request then the <a>user agent</a>
  1360             MUST abort these steps.
  1361           </li>
  1362           <li>On receiving a valid 200 OK response, run the following steps:
  1363             <ol class="rule">
  1364               <li>Let <var>callback ID</var> equal the string value of the first included <em>SID</em> header, if it
  1365               exists.
  1366               </li>
  1367               <li>Let <var>timeout date</var> equal the sum of the current UTC date value plus the integer value of the
  1368               first included <em>TIMEOUT</em> header (minus the leading string of <code>Second-</code>), if it exists.
  1369               </li>
  1370               <li>Run the following steps asynchronously and continue to the step labeled <em>listen</em> below.
  1371               </li>
  1372               <li>
  1373                 <em>Refresh Subscription</em>: Run the following steps at a set interval (X) within the <a>user
  1374                 agent</a>:
  1375                 <ol class="rule">
  1376                   <li>Let <var>current date</var> equal the current UTC date.
  1377                   </li>
  1378                   <li>If <var>current date</var> is less than the <var>timeout date</var> then continue to the step
  1379                   labeled <em>refresh subscription</em> above.
  1380                   </li>
  1381                   <li>Send a HTTP SUBSCRIBE request with a <em>SID</em> header with the string value of <var>callback
  1382                   ID</var> and a user-agent defined <em>TIMEOUT</em> header (in the form <code>Second-XX</code> where
  1383                   <code>XX</code> is the user-agent defined timeout value in seconds) towards the <var>network service
  1384                   record</var>'s <code>eventsUrl</code> property.
  1385                   </li>
  1386                   <li>On receiving a valid 200 OK, update <var>callback ID</var> with the string value of the first
  1387                   included <em>SID</em> header, if it exists. All other HTTP responses should cause the <a>user
  1388                   agent</a> to continue from the step labeled <em>refresh subscription</em> above.
  1389                   </li>
  1390                 </ol>
  1391               </li>
  1392               <li>
  1393                 <em>Listen</em>: For each HTTP NOTIFY request received at the <var>callback URL</var> the <a>user
  1394                 agent</a> is to run the following steps:
  1395                 <ol class="rule">
  1396                   <li>Let <var>content clone</var> be the result of obtaining the message body of the HTTP NOTIFY
  1397                   request. If <var>content clone</var> is empty, then the <a>user agent</a> MUST
  1398                   abort these steps.
  1399                   </li>
  1400                   <li>Let <var>notification event</var> be a new simple event that uses the <a href=
  1401                   "http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1402                         class="externalDFN"><code>Event</code></a> interface with the name <a href=
  1403                         "#event-notify"><code>notify</code></a>, which does not bubble, is not cancellable, and has no
  1404                         default action.
  1405                   </li>
  1406                   <li>Let the <code>data</code> attribute of <var>notification event</var> have the DOMString value of
  1407                   <var>content clone</var>.
  1408                   </li>
  1409                   <li>
  1410                     <a href="http://www.whatwg.org/specs/web-apps/current-work/complete/webappapis.html#queue-a-task"
  1411                         class="externalDFN">Queue a task</a> to dispatch <var>notification event</var> at the current
  1412                         <a><code>NetworkService</code></a> object.
  1413                   </li>
  1414                 </ol>
  1415               </li>
  1416             </ol>
  1417           </li>
  1418         </ol>
  1419         <p>
  1420           A <a>user agent</a> can <dfn>terminate an existing UPnP Events Subscription</dfn> at any time for any
  1421           <var>active service</var> in the <a>list of authorized service records</a> by sending an HTTP UNSUBSCRIBE
  1422           request - as defined in 'Section 4.1.4: Cancelling a subscription with UNSUBSCRIBE' in [[!UPNP-DEVICEARCH11]]
  1423           - with a HOST header set to that <var>active service</var>'s <code>eventsUrl</code> property and a SID header
  1424           set to the <var>callback ID</var> obtained when the initial <a>setup a UPnP Events Subscription</a> action
  1425           occurred.
  1426         </p>
  1427       </section>
  1428       <section>
  1429         <h3>
  1430           Network Topology Monitoring
  1431         </h3>
  1432         <div>
  1433           <p>
  1434             When the <a>user agent</a> detects that the user has dropped from their connected network then, for each
  1435             <var>existing service record</var> in the <a>list of available service records</a>, the user agent
  1436             MUST run the general rule for <a>removing an available service</a> passing in each
  1437             <var>existing service record</var>'s <code>id</code> property as the only argument for each call.
  1438           </p>
  1439           <p>
  1440             When the <a>user agent</a> detects that the user has connected to a new network or reconnected to an
  1441             existing network, then it SHOULD restart its discovery mechanisms as defined in the
  1442             <a href="#service-discovery">Service Discovery</a> section of this specification, maintaining the existing
  1443             <a>list of authorized service records</a> currently in use.
  1444           </p>
  1445         </div>
  1446       </section>
  1447     </section>
  1448     <section>
  1449       <h3>
  1450         Events Summary
  1451       </h3>
  1452       <p>
  1453         The following events are dispatched on the <a href="#networkservices"><code>NetworkServices</code></a> and/or
  1454         <a href="#networkservice"><code>NetworkService</code></a> objects:
  1455       </p>
  1456       <table border="1">
  1457         <thead>
  1458           <tr>
  1459             <th>
  1460               <span>Event name</span>
  1461             </th>
  1462             <th>
  1463               <span>Interface</span>
  1464             </th>
  1465             <th>
  1466               <span>Dispatched when...</span>
  1467             </th>
  1468           </tr>
  1469         </thead>
  1470         <tbody>
  1471           <tr>
  1472             <td>
  1473               <dfn id="event-serviceavailable"><code>serviceavailable</code></dfn>
  1474             </td>
  1475             <td>
  1476               <a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1477                   class="externalDFN"><code>Event</code></a>
  1478             </td>
  1479             <td>
  1480               When a new service that matches one of the <a>requested type tokens</a> is found in the current network.
  1481             </td>
  1482           </tr>
  1483           <tr>
  1484             <td>
  1485               <dfn id="event-serviceunavailable"><code>serviceunavailable</code></dfn>
  1486             </td>
  1487             <td>
  1488               <a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1489                   class="externalDFN"><code>Event</code></a>
  1490             </td>
  1491             <td>
  1492               When an existing service that matches one of the <a>requested type tokens</a> gracefully leaves or
  1493               expires from the current network.
  1494             </td>
  1495           </tr>
  1496           <tr>
  1497             <td>
  1498               <dfn id="event-serviceonline"><code>serviceonline</code></dfn>
  1499             </td>
  1500             <td>
  1501               <a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1502                   class="externalDFN"><code>Event</code></a>
  1503             </td>
  1504             <td>
  1505               When a current service renews its service registration within the current network.
  1506             </td>
  1507           </tr>
  1508           <tr>
  1509             <td>
  1510               <dfn id="event-serviceoffline"><code>serviceoffline</code></dfn>
  1511             </td>
  1512             <td>
  1513               <a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1514                   class="externalDFN"><code>Event</code></a>
  1515             </td>
  1516             <td>
  1517               When a current service gracefully leaves or otherwise expires from the current network.
  1518             </td>
  1519           </tr>
  1520           <tr>
  1521             <td>
  1522               <dfn id="event-notify"><code>notify</code></dfn>
  1523             </td>
  1524             <td>
  1525               <a href="http://dvcs.w3.org/hg/domcore/raw-file/tip/Overview.html#event"
  1526                   class="externalDFN"><code>Event</code></a>
  1527             </td>
  1528             <td>
  1529               When a valid UPnP Events Subscription Message is received on a <a>user-agent generated callback url</a>
  1530               for a current service. This event never fires for Zeroconf-based services.
  1531             </td>
  1532           </tr>
  1533         </tbody>
  1534       </table>
  1535     </section>
  1536     <section>
  1537       <h3>
  1538         Garbage collection
  1539       </h3>
  1540       <p>
  1541         Only when the user navigates away from the current browsing context can <a><code>NetworkService</code></a>
  1542         objects be garbage-collected, its records in the <a>entry script origin's URL whitelist</a> be removed and its
  1543         corresponding entry in the <a>list of authorized service records</a> be removed according to passing each
  1544         expired object identifier through the rule for <a>removing an available service</a>.
  1545       </p>
  1546     </section>
  1547     <section>
  1548       <h3>
  1549         Use Cases and Requirements
  1550       </h3>
  1551       <p>
  1552         This section covers what the requirements are for this API, as well as illustrates some use cases.
  1553       </p>
  1554       <ul class="rule">
  1555         <li>Once a user has given permission, user agents should provide the ability for Web pages to communicate
  1556         directly with a Local-networked Service.
  1557           <ul class="rule">
  1558             <li>Example: A web-based TV remote control. A Web page wants to control the current user's TV, changing the
  1559             programming shown or increasing/decreasing/muting the volume of the Local-networked Device. The Web page
  1560             requests a service type that is known to be implemented by television sets to which it has the application
  1561             logic to communicate. Local devices providing the request service types are discovered and presented to the
  1562             user for authorization. The user selects one or more of the discovered television sets to be accessible to
  1563             the current Web page and then clicks 'Share'. The Web page can now communicate directly with the
  1564             user-authorized Local-networked services.
  1565             </li>
  1566           </ul>
  1567         </li>
  1568         <li>Web pages should be able to communicate with Local-networked Services using the messaging channel supported
  1569         by those Devices.
  1570           <ul class="rule">
  1571             <li>Example: A Web page advertises that it is capable of controlling multiple Home Media Servers. The user
  1572             can select their Home Media Server type from a drop-down list, at which point the Web page sends a request
  1573             to the user agent to connect with the associated service type of the Home Media Server. The Media Server
  1574             selected implements a Web Socket channel for bi-directional service communication and so the Web page opens
  1575             a web socket to the requested Media Server and can communicate as required via that appropriate channel.
  1576             </li>
  1577           </ul>
  1578         </li>
  1579         <li>Web pages should be able to communicate with Local-networked Services using the messaging format supported
  1580         by those Devices.
  1581           <ul class="rule">
  1582             <li>Example: A Web page advertises that it is capable of interacting with and controlling multiple types of
  1583             Home Media Server. The user can select their Home Media Server type from a drop-down list or known Media
  1584             Servers, at which point the Web page sends a request to the user agent to connect with the associated
  1585             service type (and, optionally, the associated event type) of the Home Media Server. The communication
  1586             protocols supported by Home Media Servers typically vary between UPnP, JSON-RPC, Protocol Buffers or other
  1587             messaging formats depending on the Home Media Server requested. The Web page is able to communicate with
  1588             the user-selected Home Media Server in the messaging format supported by that Device, which, in this
  1589             example is a simple key/value pair text format.
  1590             </li>
  1591           </ul>
  1592         </li>
  1593         <li>Web pages should not be able to communicate with Local-networked Services that have not been authorized by
  1594         the user thereby maintaining the user's privacy.
  1595           <ul class="rule">
  1596             <li>Example: A Web page requests access to one type of Local-networked service. The user authorizes access
  1597             to that particular service. Other services running on that same device, and on other devices within the
  1598             network, should not be accessible to the current Web page.
  1599             </li>
  1600           </ul>
  1601         </li>
  1602         <li>A user should be able to share one or more Local-networked Services based on a particular service type
  1603         request from a Web page.
  1604           <ul class="rule">
  1605             <li>Example: A Web page is capable of interacting with a specific profile of Local-networked Service. As
  1606             such, it makes a request to the user agent to access those services, of which multiple matches are found.
  1607             The user is capable of selecting one or more of the discovered services to share with the Web page. The Web
  1608             page can then implement a drag-and-drop interface for the user to drag specific actions on to one or more
  1609             of the authorized Local-networked Services.
  1610             </li>
  1611           </ul>
  1612         </li>
  1613         <li>User agents should provide an API exposed to script that exposes the features above. The user is notified
  1614         by UI anytime interaction with Local-networked Services is requested, giving the user full ability to cancel or
  1615         abort the transaction. The user selects the Local-networked Services to be connected to the current Web page,
  1616         and can cancel these at any time. No invocations to these APIs occur silently without user intervention.
  1617         </li>
  1618       </ul>
  1619     </section>
  1620     <section class="informative appendix">
  1621       <h3>
  1622         Examples
  1623       </h3>
  1624       <div class="example">
  1625         <p>
  1626           This sample code exposes a button. When clicked, this button is disabled and the user is prompted to offer a
  1627           network service. The user may also select multiple network services. When the user has authorized a network
  1628           service to be connected to the web page then the web page issues a simple command to get a list of all the
  1629           albums stored on the connected media player service.
  1630         </p>
  1631         <p>
  1632           The button is re-enabled only when the connected network service disconnects for whatever reason (the service
  1633           becomes unavailable on the network, the user disconnects from their current network or the user revokes
  1634           access to the service from the current web page). At this point the user can re-click the button to select a
  1635           new network service to connect to the web page and the above steps are repeated.
  1636         </p>
  1637         <p>
  1638           The provided service type identifier and service interaction used in this example is based on the
  1639           well-defined service type and messaging format supported by the <a href="http://xbmc.org/about/">XBMC Media
  1640           Server</a>.
  1641         </p>
  1642         <hr>
  1643         <pre class="highlight">
  1644 &lt;input type="button" value="Start" onclick="start()" id="startBtn"/&gt;
  1645 &lt;div id="debugconsole"&gt;&lt;/div&gt;
  1646 
  1647 &lt;script&gt;
  1648  var startBtn = document.getElementById('startBtn'),
  1649      debug = document.getElementById('debugconsole');
  1650 
  1651  function start() {
  1652    if(navigator.getNetworkServices) {
  1653       navigator.getNetworkServices('zeroconf:_xbmc-jsonrpc._tcp', gotXBMCService, error);
  1654       startBtn.disabled = true;
  1655    } else {
  1656       debug.innerHTML += "&lt;br&gt;Service Discovery not supported!";
  1657    }
  1658  }
  1659 
  1660  function gotXBMCService(services) {
  1661 
  1662 // Listen for service disconnect messages
  1663 
  1664    services[0].addEventListener('serviceoffline', function ( e ) {
  1665        debug.innerHTML += "&lt;br&gt;" + services[0].name + " disconnected.";
  1666        startBtn.disabled = false;
  1667    }, false);
  1668 
  1669 // Send a service message to get albums list (and process the service response)
  1670 
  1671    var svcXhr = new XMLHttpRequest();
  1672    svcXhr.open("POST", services[0].url + "/getAlbums"); // services[0].url and its sub-resources have been
  1673                                                         // whitelisted for cross-site XHR use in this
  1674                                                         // current browsing context.
  1675 
  1676    svcXhr.setRequestHeader('Content-Type', 'application/json-rpc');
  1677 
  1678    svcXhr.addEventListener('readystatechange', function ( response ) {
  1679      if( response.readyState != 4 || response.status != 200 )
  1680         return;
  1681      debug.innerHTML += "&lt;br&gt;" + services[0].name + " response received: ";
  1682      debug.textContent += JSON.parse(response.responseText);
  1683    }, false);
  1684 
  1685    var svcMsg = [
  1686      { "jsonrpc": "2.0", "method": "AudioLibrary.GetAlbums", "params": { "genreid": -1,
  1687          "artistid": -1, "start": -1, "end": -1 }, "id": "1" }
  1688    ];
  1689 
  1690    svcXhr.send(JSON.stringify(svcMsg));
  1691    debug.innerHTML += "&lt;br&gt;" + services[0].name + " request sent: ";
  1692    debug.textContent += JSON.stringify(svcMsg);
  1693 
  1694  }
  1695 
  1696  function error( err ) {
  1697    debug.innerHTML += "&lt;br&gt;An error occurred obtaining a local network service.";
  1698    startBtn.disabled = false;
  1699  }
  1700 &lt;/script&gt;
  1701 </pre>
  1702       </div>
  1703       <div class="example">
  1704         <p>
  1705           This sample exposes a drop-down list containing a number of common Home-based audio devices. When the user
  1706           selects an audio device from the list provided, they are prompted to authorize a network service based on the
  1707           service type requested. The user may also select multiple network services matching the selected service
  1708           type. In this example, the user selects their make as being <var>Sony</var> and their model as being
  1709           <var>Bravia S1000</var> from which the Web page can derive a service type
  1710           (<var>urn:schemas-upnp-org:service:RenderingControl:1</var>).<br>
  1711           <br>
  1712           Once the user has authorized the device, the web page sends a simple mute command according to the messaging
  1713           format supported by the device.
  1714         </p>
  1715         <hr>
  1716         <pre class="highlight">
  1717 &lt;select name="make" id="make"&gt;
  1718   &lt;option selected="selected" disabled="disabled"&gt;Select make&lt;/option&gt;
  1719   &lt;option&gt;Sony&lt;/option&gt;
  1720   &lt;option&gt;Philips&lt;/option&gt;
  1721   &lt;option&gt;Alba&lt;/option&gt;
  1722 &lt;/select&gt;
  1723 &lt;select name="model" id="model"&gt;&lt;/select&gt;
  1724 &lt;div id="debugconsole"&gt;&lt;/div&gt;
  1725 
  1726 &lt;script&gt;
  1727   var debug = document.getElementById('debugconsole');
  1728 
  1729   var models = {
  1730     "Sony": [
  1731       {"name": "Bravia TV S1000", "type": "upnp", "service": "urn:schemas-upnp-org:service:RenderingControl:1" },
  1732       {"name": "Bravia TV S2000", "type": "zeroconf", "service": "_mediarenderer._http._tcp" },
  1733       {"name": "HiFi WD10", "type": "upnp", "service": "urn:schemas-upnp-org:service:RenderingControl:1" }
  1734     ],
  1735     "Philips": [ /* ... */ ],
  1736     "Alba": [ /* ... */ ]
  1737   };
  1738 
  1739   var makeEl = document.getElementById("make"),
  1740       modelEl = document.getElementById("model");
  1741 
  1742   makeEl.addEventListener('change', function() {
  1743     modelEl.innerHTML = ""; // reset
  1744     var defaultOption = document.createElement("option");
  1745     defaultOption.textContent = "Select model";
  1746     defaultOption.setAttribute("disabled", "disabled");
  1747     defaultOption.setAttribute("selected", "selected");
  1748     modelEl.appendChild(defaultOption);
  1749     for(var i = 0, l = models[makeEl.value].length; i &lt; l; i++) {
  1750       var option = document.createElement("option");
  1751       option.textContent = models[makeEl.value][i]["name"];
  1752       option.setAttribute("value", models[makeEl.value][i]["type"] + ":" + models[makeEl.value][i]["service"]);
  1753       modelEl.appendChild(option);
  1754     }
  1755   }, false);
  1756 
  1757   modelEl.addEventListener('change', function() {
  1758     if(navigator.getNetworkServices &amp;&amp;
  1759          modelEl.value == "upnp:urn:schemas-upnp-org:service:RenderingControl:1") {
  1760       navigator.getNetworkServices(modelEl.value, successCallback, errorCallback);
  1761     } else if (modelEl.value == "zeroconf:_mediarenderer._http._tcp") {
  1762       debug.innerHTML += "&lt;br&gt;Service type is not implemented by this application.";
  1763     } else {
  1764       debug.innerHTML += "&lt;br&gt;Service Discovery is not supported!";
  1765     }
  1766   }, false);
  1767 &lt;/script&gt;
  1768 
  1769 &lt;script&gt;
  1770   function successCallback( services ) {
  1771 
  1772   // Listen for service push notification messages
  1773 
  1774     services[0].addEventListener('notify', function ( msg ) {
  1775          debug.innerHTML += "&lt;br&gt;" + services[0].name + " event received: ";
  1776          debug.textContent += msg.data;
  1777     }, false);
  1778 
  1779  // Send a control signal to mute the service audio
  1780 
  1781     var svcXhr = new XMLHttpRequest();
  1782     svcXhr.open("POST", services[0].url); // services[0].url and its
  1783                                           // sub-resources have been whitelisted for
  1784                                           // cross-site XHR use in this current
  1785                                           // browsing context.
  1786 
  1787     svcXhr.setRequestHeader('SOAPAction', 'urn:schemas-upnp-org:service:RenderingControl:1#SetMute');
  1788     svcXhr.setRequestHeader('Content-Type', 'text/xml; charset="utf-8";');
  1789 
  1790     svcXhr.onreadystatechange = function ( response ) {
  1791       if( response.readyState != 4 || response.status != 200 )
  1792         return;
  1793       debug.innerHTML += "&lt;br&gt;" + services[0].name + " response received: ";
  1794       debug.textContent += response.responseXML;
  1795     }
  1796 
  1797     // Service messaging to mute the provided service
  1798     var svcMsg = '&lt;?xml version="1.0" encoding="utf-8"?&gt;' +
  1799                  '&lt;s:Envelope s:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/" ' +
  1800                    'xmlns:s="http://schemas.xmlsoap.org/soap/envelope/"&gt;' +
  1801                    '&lt;s:Body&gt;' +
  1802                      '&lt;u:SetMute xmlns:u="urn:schemas-upnp-org:service:RenderingControl:1"&gt;' +
  1803                        '&lt;InstanceID&gt;0&lt;/InstanceID&gt;' +
  1804                        '&lt;Channel&gt;Master&lt;/Channel&gt;' +
  1805                        '&lt;DesiredMute&gt;true&lt;/DesiredMute&gt;' +
  1806                      '&lt;/u:SetMute&gt;' +
  1807                    '&lt;/s:Body&gt;' +
  1808                  '&lt;/s:Envelope&gt;';
  1809 
  1810     svcXhr.send(svcMsg);
  1811     debug.innerHTML += "&lt;br&gt;" + services[0].name + " request sent: ";
  1812     debug.textContent += svcMsg;
  1813   }
  1814 
  1815   function errorCallback( error ) {
  1816     debug.innerHTML += "&lt;br&gt;An error occurred: " + error.code;
  1817   }
  1818 &lt;/script&gt;
  1819 </pre>
  1820       </div>
  1821     </section>
  1822     <section>
  1823       <h3>
  1824         Acknowledgements
  1825       </h3>
  1826       <p>
  1827         Thanks are expressed by the editor to the following individuals for their feedback on this specification to
  1828         date (in alphabetical order):<br>
  1829         <br>
  1830         Gar Bergstedt, Lars-Erik Bolstad, Cathy Chan, Hari G Kumar, Bob Lund, Giuseppe Pascale, Marcin Simonides,
  1831         Clarke Stevens, Christian Söderström, Mark Vickers.
  1832       </p>
  1833       <p>
  1834         Thanks are also expressed by the editor to the following organizations and groups for their support in
  1835         producing this specification to date (in alphabetical order):<br>
  1836         <br>
  1837         CableLabs, Opera Software ASA, W3C Device APIs Working Group, W3C Web and TV Interest Group.
  1838       </p>
  1839     </section>
  1840   </body>
  1841 </html>