--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/wi-addendum-local-services/Overview.html Sun Sep 02 11:11:35 2012 +0200
@@ -0,0 +1,736 @@
+<!DOCTYPE html>
+<html>
+ <head>
+ <title>Web Intents Addendum - Local Services</title>
+ <meta http-equiv='Content-Type' content='text/html;charset=utf-8'/>
+ <!--
+ === NOTA BENE ===
+ For the three scripts below, if your spec resides on dev.w3 you can check them
+ out in the same tree and use relative links so that they'll work offline,
+ -->
+ <script src='http://www.w3.org/Tools/respec/respec-w3c-common' class='remove'></script>
+ <script class='remove'>
+ var respecConfig = {
+ // specification status (e.g. WD, LCWD, NOTE, etc.). If in doubt use ED.
+ specStatus: "ED",
+
+ // the specification's short name, as in http://www.w3.org/TR/short-name/
+ shortName: "Web Intents-LD addendum",
+
+ // if your specification has a subtitle that goes below the main
+ // formal title, define it here
+ // subtitle : "an excellent document",
+
+ // if you wish the publication date to be other than today, set this
+ // publishDate: "2009-08-06",
+
+ // if the specification's copyright date is a range of years, specify
+ // the start date here:
+ // copyrightStart: "2005"
+
+ // if there is a previously published draft, uncomment this and set its YYYY-MM-DD date
+ // and its maturity status
+ // previousPublishDate: "1977-03-15",
+ // previousMaturity: "WD",
+
+ // if there a publicly available Editor's Draft, this is the link
+ // edDraftURI: "http://dev.w3.org/2009/dap/ReSpec.js/documentation.html",
+
+ // if this is a LCWD, uncomment and set the end of its review period
+ // lcEnd: "2009-08-05",
+
+ // if you want to have extra CSS, append them to this list
+ // it is recommended that the respec.css stylesheet be kept
+ extraCSS: ["http://dev.w3.org/2009/dap/ReSpec.js/css/respec.css"],
+
+ // editors, add as many as you like
+ // only "name" is required
+ editors: [
+ { name: "Claes Nilsson",
+ company: "Sony Mobile", companyURL: "http://www.sonymobile.com/se/" },
+ { name: "Norifumi Kikkawa",
+ company: "Sony Corporation", companyURL: "http://www.sony.net/"},
+ ],
+
+ // authors, add as many as you like.
+ // This is optional, uncomment if you have authors as well as editors.
+ // only "name" is required. Same format as editors.
+
+ //authors: [
+ // { name: "Your Name", url: "http://example.org/",
+ // company: "Your Company", companyURL: "http://example.com/" },
+ //],
+
+ //
+ edDraftURI: "http://w3c-test.org/dap/wi-addendum-local-services/",
+
+ // name of the WG
+ wg: "DAP/Web Apps Web Intents task force",
+
+ // URI of the public WG page
+ wgURI: "http://www.w3.org/2009/dap/",
+
+ // name (without the @w3c.org) of the public mailing to which comments are due
+ wgPublicList: "public-web-intents",
+
+ // URI of the patent status for this WG, for Rec-track documents
+ // !!!! IMPORTANT !!!!
+ // This is important for Rec-track documents, do not copy a patent URI from a random
+ // document unless you know what you're doing. If in doubt ask your friendly neighbourhood
+ // Team Contact.
+ wgPatentURI: "",
+ };
+ </script>
+ </head>
+ <body>
+ <section id='abstract'>
+ This specification is an addendum to Web Intents, [[!WEBINTENTS]], that defines how Web Intents enabled User Agents can discover and communicate
+ with local Web Intents Services.
+ </section>
+
+ <section class='informative'>
+ <h2>Introduction</h2>
+ <p>
+ Web Intents,[[!WEBINTENTS]], is a service discovery and light-weight RPC mechanism for web applications. The concept enables rich integration between web applications.
+ A typical Web Intents scenario is:
+ </p>
+ <ol>
+ <li>Web Intents Services register their intention to handle an action for the user </li>
+ <li>A web application requests to start an action (share, edit, pick, view, ...)</li>
+ <li>The user selects which service to handle the action</li>
+ </ol>
+ <p>
+ A Web Intents Service is represented by a web page that declaratively marks itself as providing handling functionality for particular intents. Users register Web Intents Services
+ by visiting web pages that contain registration markup.
+ However, the strength of Web Intents is the ability to provide web applications with access to Services residing not only in the cloud but also in local environments.
+ </p>
+ <p>
+ This specification defines optional extensions to Web Intents enabled User Agents to discover and dynamically register local Web Intents
+ Services. Note that all details of the specific low level protocols used to discover and communicate with the local services are hidden to
+ the Client Web Applications.
+ </p>
+ <p>
+ The following code illustrates how a web application containing links to videos, can initiate video playback by creating and invoking a "video intent" as defined in [[!WEBINTENTS]].
+ This code is the same irrespective of whether the Service executing the intent action is a cloud based Service or a local Service.
+ </p>
+ <pre class="example sh_javascript_dom">
+
+ // Create a new intent
+var intent = new Intent( "http://webintents.org/view","video/mp4",{ "src":videoCanvas.src, "img": videoCanvas.poster});
+
+// Start intents picker
+navigator.startActivity(intent,
+ // On Result
+ function(intentData) {console.log("player.html: On Result" + intentData);},
+ // On Failure
+ function(intentData) {console.log("player.html: On Failure" + intentData);});
+ </pre>
+ <p>
+ The example below briefly describes the steps taken when a Service on a local network, e.g. UPnP or mDNS, device is discovered and selected by
+ the user.
+ </p>
+
+ <ol>
+ <li>Triggered by navigator.startActivity the User Agent will start local network discovery of Web Intents Services.</li>
+ <li>Replies from Web Intents enabled devices contain a URL to a Web Intents document, containing Web Intents Service registration
+ markup, in the device. </li>
+ <li>The Web Intents documents are retrieved by the User Agent and the dynamically registered Services are visible in the Web Intents Service picker. </li>
+ <li>User selects Service.</li>
+ <li>User Agent retrieves the Service page from the the Web Intents local network device and invokes it. </li>
+ <li>The Service page handles the intent. </li>
+ <li>When handling the intent is finished, the Service page issues window.intent.postResult and closes itself. </li>
+ </ol>
+
+ </section>
+
+ <section id="conformance">
+ <p>
+ This specification defines conformance criteria that apply to:
+ <ul>
+ <li><dfn>UPnP enabled User Agent</dfn>: A <a>UPnP enabled User Agent</a> MUST support Web Intents [[!WEBINTENTS]] and the conformance criteria
+ stated in this specification. </li>
+ <li><dfn>Web Intents enabled UPnP device</dfn>: A <a>Web Intents enabled UPnP device</a> MUST support [[!UPNP-DEVICEARCH]] and the conformance criteria
+ stated in this specification. </li>
+ <li><dfn>mDNS enabled User Agent</dfn>: An <a>mDNS enabled User Agent</a> MUST support Web Intents [[!WEBINTENTS]] and the conformance criteria
+ stated in this specification. </li>
+ <li><dfn>Web Intents enabled mDNS device</dfn>: A <a>Web Intents enabled mDNS device</a> MUST support [[!DNS-SD]], [[!MDNS]] and the conformance criteria
+ stated in this specification. </li>
+ </ul>
+ </p>
+ <p>
+ Implementations that use ECMAScript to implement the APIs defined in
+ this specification must implement them in a manner consistent with the
+ ECMAScript Bindings defined in the Web IDL specification [[!WEBIDL]],
+ as this specification uses that specification and terminology.
+ </p>
+ <section>
+ <h2>Dependencies</h2>
+ <p>
+ This specification relies on the following specifications:
+
+ <dl>
+ <dt>Web Intents</dt>
+ <dd>This addendum specification is dependent on and defines optional extensions to the basic Web Intents specification, [[!WEBINTENTS]]. </dd>
+ <dt>UPnP Device Architecture 1.0</dt>
+ <dd>This addendum specification is dependent on and defines vendor specific extensions to the UPnP Device Architecture 1.0 specification, [[!UPNP-DEVICEARCH]]. </dd>
+ <dt>IANA Service Name and Transport Protocol Port Number Registry</dt>
+ <dd>This addendum specification adds new entry on it, [[!IANA-SRVPORT-REG]]. </dd>
+ <dt>DNS-SD</dt>
+ <dd>This addendum specification is dependent on it, [[!DNS-SD]]. </dd>
+ <dt>mDNS</dt>
+ <dd>This addendum specification is dependent on it, [[!MDNS]]. </dd>
+ </dl>
+
+ </p>
+ </section>
+ </section>
+
+ <section>
+ <h2>Terminology</h2>
+ <p>
+ Web Intents related terms are used according to section "Terminology" in [[!WEBINTENTS]].
+ </p>
+
+ <section>
+ <h3>UPnP related terms</h3>
+ <p>
+ UPnP related terms are used according to [[!UPNP-DEVICEARCH]].
+ </p>
+ <p>
+ The <a>UPnP enabled User Agent</a> has the role of a <dfn id="dfn-registration">control point</dfn> according to UPnP terminology.
+ </p>
+ <p>
+ The <a>Web Intents enabled UPnP device</a> discovered by the <a>UPnP enabled User Agent</a> has the roles of <dfn id="dfn-registration">device</dfn> according to UPnP terminology.
+ </p>
+ </section>
+
+ <section>
+ <h3>mDNS related terms</h3>
+ <p>
+ The <a>mDNS enabled User Agent</a> has the role of a <dfn id="dfn-registration">DNS client</dfn> with capability of [[!DNS-SD]].
+ </p>
+ <p>
+ The <a>Web Intents enabled mDNS device</a> discovered by the <a>mDNS enabled User Agent</a> has the roles of <dfn id="dfn-registration">service</dfn> according to [[!MDNS]] and [[!DNS-SD]].
+ </p>
+ </section>
+
+
+ </section>
+
+ <section>
+
+ <h2>UPnP adaptation</h2>
+
+ <section>
+
+ <h3><a>Web Intents enabled UPnP device</a></h3>
+
+ <p>
+ The <a>Web Intents enabled UPnP device</a> <em class="rfc2119" title="must">must</em> support this section.
+ </p>
+
+ <section>
+
+ <h4>UPnP Web Intents serviceType</h4>
+
+ <p>
+ The <a>Web Intents enabled UPnP device</a> <em class="rfc2119" title="must">must</em> support one UPnP service which serviceType is the <code>urn:schemas-webintents-org:service:WebIntents:1</code>
+ as a vendor specific serviceType according to [[!UPNP-DEVICEARCH]]. It is vendor dependent how the <a>Web Intents enabled UPnP device</a> implements the serviceType,
+ i.e. a device description of any deviceType could include this serviceType.
+ </p>
+
+ <p>
+ The Web Intents serviceType <em class="rfc2119" title="must">must</em> have a dummy state variable, <code>X_State</code> of <code>boolean</code> data type to comform to [[!UPNP-DEVICEARCH]]
+ which requires one or more state variables in a serviceType. The <code>X_State</code> state variable is not used with a value and is never evented.
+ </p>
+ <p>
+ The Web Intents serviceType has no standard action.
+ </p>
+
+ <p>
+ See below for the UPnP Service description document of the Web Intents serviceType.
+ </p>
+
+ <p align="left"><img src="Example_device_and_service_description_pages/Slide2.png" alt="Service description page" width="600" height="600" ><br>
+ (<a href="Example_device_and_service_description_pages/Slide2.png">View as PNG</a>)
+ </p>
+
+
+ </section>
+
+ <section>
+
+ <h4>Web Intents specific SSDP headers</h4>
+
+ <p>
+ The <a>Web Intents enabled UPnP device</a> <em class="rfc2119" title="must">must</em> support SSDP discovery process based on standard UPnP Discovery extended with 2 additional
+ SSDP headers for M-SEARCH response and NOTIFY when ST/NT headers are:<code>urn:schemas-webintents-org:service:WebIntents:1</code>
+ </p>
+
+ <ul>
+ <li>
+ <code>location.webintents.org</code>: <em class="rfc2119" title="required">required</em>. States the location to the Web Intents document in the <a>Web Intents enabled UPnP device</a>.
+ If the value of this header is a relative URL the base URL is the base URL of the <code>LOCATION</code> header.
+ </li>
+ <li>
+ <code>action.webintents.org</code>: <em class="rfc2119" title="optional">optional</em>. If supported, states the Web Intents
+ <code>action</code> of the supported Web Intents Services and <em class="rfc2119" title="must">must</em>
+ match the <code>action</code> attributes of the Service registration markup in the Web Intents document. To support more than
+ one Web Intents <code>action</code> the action strings <em class="rfc2119" title="must">must</em> be separated with
+ comma. Commas included in action strings <em class="rfc2119" title="must">must</em> be percent-encoded as
+ defined in [[!RFC3986]], section-2.1.
+ <br /> <br />
+ This header allows the <a>UPnP enabled User Agent</a> to filter received SSDP messages so that the <a>UPnP enabled User Agent</a> only has to
+ retrieve Web Intents documents for matching Web Intents Actions.
+ </li>
+ </ul>
+
+ </section>
+
+ <section>
+
+ <h4>Web Intents document</h4>
+
+ <p>
+ The <a>Web Intents enabled UPnP device</a> <em class="rfc2119" title="must">must</em> host Web Intents documents for the Web Intents Services the <a>Web Intents enabled UPnP device</a> supports.
+ Web Intents documents are html pages that contain Web Intents Service registration markup according to the rules for Web Intents Service registration defined
+ by [[!WEBINTENTS]]. They may also contain Service handler code for Services registered within the same document.
+ </p>
+
+ </section>
+
+ <section>
+
+ <h4>Web Intents Service pages</h4>
+
+ <p>
+ The <a>Web Intents enabled UPnP device</a> <em class="rfc2119" title="must">must</em> host a Web Intents Service page for each Service that is
+ referred in Web Intents documents through <code>href</code> attributes in the registration markup.
+ </p>
+ <p>
+ Service pages contain Service handler code and fulfills the rules for Web Intents Services as defined by [[!WEBINTENTS]].
+ </p>
+
+ </section>
+
+ </section>
+
+ <section>
+
+ <h3><a>UPnP enabled User Agent</a></h3>
+
+ <p>
+ The <a>UPnP enabled User Agent</a> <em class="rfc2119" title="must">must</em> support discovery of <a>Web Intents enabled UPnP device<a>s through SSDP Discovery or through Advertisement
+ or through both methods according to [[!UPNP-DEVICEARCH]] and according to the Web Intents serviceType and Web Intents specific SSDP headers
+ defined in this specification, section 4.1.
+ </p>
+
+ <p>
+ The sections below describe typical steps using these methods.
+ </p>
+
+ <section class='informative'>
+ <h4>Dynamic Service registration based on M-SEARCH</h4>
+
+ <p>
+ The section describes the discovery process based on standard UPnP M-SEARCH multicast request.
+ </p>
+
+ <p>
+ When the navigator.startActivity method [[!WEBINTENTS]] is called, the <a>UPnP enabled User Agent</a> runs the following steps:
+ </p>
+
+ <ol class="rule">
+ <li>
+ Send a multicast request with the method M-SEARCH in the format specified by [[!UPNP-DEVICEARCH]].
+ <br />
+ The <code>ST</code> header is set to: <code>urn:schemas-webintents-org:service:WebIntents:1</code>
+ </li>
+ <br />
+ <li>
+ For each matching M-SEARCH response, i.e. the response ST header is <code>urn:schemas-webintents-org:service:WebIntents:1</code> and the <code>action.webintents.org</code>
+ header, if present, matches the Action of the invoked intent,
+ the <a>UPnP enabled User Agent</a> attempts to retrieve the Web Intents document from the discovered <a>Web Intents enabled UPnP device</a>.
+ The value of the <code>location.webintents.org</code> header is the location for the Web Intents document.
+ If this value is a relative URL the <a>UPnP enabled User Agent</a> uses the base URL of the <code>LOCATION</code> header as base URL for the location of the
+ Web Intents document.
+ <br /> <br />
+ If the <a>UPnP enabled User Agent</a> fails to retrieve the Web Intents document it silently disregards the received M-SEARCH response.
+ <br /> <br />
+ If the <code>action.webintents.org</code> header is present and does not match the <code>action</code> attributes of the Services registered in the retrieved Web Intents
+ document the <a>UPnP enabled User Agent</a> silently disregards the the received M-SEARCH response.
+ </li>
+ <br />
+ <li>
+ It is expected that the Web Intents document contains registration markup and the <a>UPnP enabled User Agent</a> interprets this
+ registration markup according to the rules for registration defined by [[!WEBINTENTS]] and register the Services accordingly.
+ </li>
+ <br />
+ <li>
+ The <a>UPnP enabled User Agent</a> makes each dynamically registered Service, that matches the Action of the invoked intent, available for selection
+ by the user, typically by making them visible and selectable in a Web Intents Service picker.
+ </li>
+ <br />
+ <li>
+ Based on user selection of a dynamically registered Service the <a>UPnP enabled User Agent</a> loads the
+ Service handler code as defined by the <code>href</code> attribute in the registration markup for this Service according to the rules for
+ loading Service pages defined in [[!WEBINTENTS]].
+ </li>
+
+ </ol>
+
+ </section>
+
+ <section class='informative'>
+ <h4>Dynamic Service registration based on NOTIFY</h4>
+ <p>
+ This section describes the discovery process based on standard UPnP Advertisement with NOTIFY message.
+ </p>
+
+ <p>
+ The <a>UPnP enabled User Agent</a> <em class="rfc2119" title="may">may</em> continuously listen to and act on advertisments according to the following steps:
+ </p>
+ <ol class="rule">
+
+ <li>
+ The <a>UPnP enabled User Agent</a> maintains a list of announced UPnP services based on received SSDP NOTIFY messages
+ with <code>NT</code> header equal to <code>urn:schemas-webintents-org:service:WebIntents:1</code>.
+ </li>
+ <br />
+ <li>
+ When the navigator.startActivity method [[!WEBINTENTS]] is called the <a>UPnP enabled User Agent</a> checks the list
+ of of announced services and attempts to retrieve the Web Intents document from the discovered <a>Web Intents enabled UPnP device</a> in the following cases:
+ <ul>
+ <li>
+ The received NOTIFY message contains an <code>action.webintents.org</code> header and this header matches the Action of the invoked intent.
+ </li>
+ <li>
+ The received NOTIFY message does not contain an <code>action.webintents.org</code> header.
+ </li>
+ </ul>
+ <br />
+ The location of the Web Intents document is the value of the <code>location.webintents.org</code> header. If this value is a relative URL the
+ base URL is the base URL of the <code>LOCATION</code> header.
+ <br /> <br />
+ If the <a>UPnP enabled User Agent</a> fails to retrieve the Web Intents document it silently disregards the received NOTIFY message.
+ <br /> <br />
+ If the <code>action.webintents.org</code> header does not match the <code>action</code> attribute in the retrieved Web Intents document
+ the <a>UPnP enabled User Agent</a> silently disregards the received NOTIFY message.
+ </li>
+ <br />
+ <li>
+ It is expected that the Web Intents document contains registration markup and the <a>UPnP enabled User Agent</a> interprets the
+ Web Intents document according to the rules for registration defined by [[!WEBINTENTS]] and register the Services accordingly.
+ </li>
+ <br />
+ <li>
+ The <a>UPnP enabled User Agent</a> makes each dynamically registered Service, that matches the Action of the invoked intent, available for selection
+ by the user, typically by making them visible and selectable in a Web Intents Service picker.
+ </li>
+ <br />
+ <li>
+ Based on user selection of a dynamically registered Service the <a>UPnP enabled User Agent</a> loads the
+ Service handler code as defined by the <code>href</code> attribute in the registration markup for this Service according to the rules for
+ loading Service pages defined in [[!WEBINTENTS]].
+ </li>
+ </ol>
+
+ <p class="note">
+ Power consumption in battery powered devices should be considered. If power consumption is severe continuously listening to SSDP advertisement in the background
+ should not be used..
+ </p>
+
+ </section>
+
+ <section class='informative'>
+ <h4>Support for Web Intents and UPnP</h4>
+ <p>
+ In addition to the normative statements defined in this specification a <a>UPnP enabled User Agent</a> that complies to this specification
+ supports Web Intents according to [[!WEBINTENTS]] and UPnP Discovery, Description and Control according to [[!UPNP-DEVICEARCH]].
+ However, it is implementation dependent whether this is supported natively in the User Agent or supported through some external component,
+ e.g. an in-device web server.
+ </p>
+ </section>
+
+ <section class='informative'>
+
+ <h4>Service availability management</h4>
+
+ <p>
+ The <a>UPnP enabled User Agent</a> should manage the availability of UPnP services. For example detect when contact with a <a>Web Intents enabled UPnP device</a> is lost through standard
+ UPnP life cycle management and remove a previously discovered and registered Service from the Service picker. However, for battery powered devices
+ power consumption should be considered and long lasting "keep alive" sessions" should be avoided.
+ </p>
+
+ </section>
+
+ </section>
+
+
+
+ </section>
+
+ <section>
+
+ <h2>mDNS (DNS-SD) adaptation</h2>
+
+ <p>
+ This section describes how the User Agent handles Web Intents Services provided by local devices supporting mDNS and DNS-SD.
+ </p>
+
+ <section>
+
+ <h3>Web Intents enabled mDNS device</h3>
+
+ <p>
+ The <a>Web Intents enabled mDNS device</a> <em class="rfc2119" title="must">must</em> support this section.
+ </p>
+
+ <section>
+
+ <h4>Web Intents service type for DNS-SD</h4>
+
+ <p>
+ The <a>Web Intents enabled mDNS device</a> <em class="rfc2119" title="must">must</em> support [[!DNS-SD]] with a SRV record of the <code>webintents</code> service type.
+ </p>
+
+ <p class="note">
+ A service type <code>webintents</code> should be registered in [[!IANA-SRVPORT-REG]].
+ </p>
+
+ <p>
+ The TXT record for the <code>webintents</code> service must have following parameters:
+ </p>
+ <ul>
+ <li>
+ <code>location</code>: <em class="rfc2119" title="required">required</em>. States the location to the Web Intents document in the <a class="internalDFN" href="#dfn-web-intents-enabled-mdns-device">Web Intents enabled mDNS device</a>.
+ The value of this header is path to be concatenated with a host of the <a class="internalDFN" href="#dfn-web-intents-enabled-mdns-device">Web Intents enabled mDNS device</a> to determine the location. The definition of the Web Intents document is the same as for UPnP.
+ </li>
+ <li>
+ <code>action</code>: <em class="rfc2119" title="optional">optional</em>. If supported, states the Web Intents
+ <code>action</code> of the supported Web Intents Services and <em class="rfc2119" title="must">must</em>
+ match the <code>action</code> attributes of the Service registration markup in the Web Intents document. To support more than
+ one Web Intents <code>action</code> the action strings <em class="rfc2119" title="must">must</em> be separated with
+ comma. Commas included in action strings <em class="rfc2119" title="must">must</em> be percent-encoded as
+ defined in [[!RFC3986]], section-2.1.
+ <br> <br>
+ This allows the <a>mDNS enabled User Agent</a> to filter received mDNS messages so that the <a>mDNS enabled User Agent</a> only has to
+ retrieve Web Intents documents for matching Web Intents Actions.
+ </li>
+ </ul>
+
+ </section>
+
+ </section>
+ <section>
+ <h3>mDNS enabled User Agent</h3>
+
+ <p>
+ The <a>mDNS enabled User Agent</a> <em class="rfc2119" title="must">must</em> support discovery of <a>Web Intents enabled mDNS device<a>s through mDNS and DNS-SD
+ according to [[!MDNS]], [[!DNS-SD]] and according to the Web Intents specific DNS records defined in this specification, section 5.1.
+ </p>
+
+ <section class='informative'>
+ <h4>Dynamic Service registration</h4>
+ <p>
+ When the navigator.startActivity method [[!WEBINTENTS]] is called, the <a>mDNS enabled User Agent</a> typically runs the following steps:
+ </p>
+
+ <ol class="rule">
+ <li>
+ Send a multicast PTR query of the <code>_webintents._tcp.local</code> in the format specified by [[!MDNS]] and [[!DNS-SD]].
+ <br />
+ </li>
+ <br />
+ <li>
+ For each response, send a unicast TXT query of the webintents service instance in the PTR answer.
+ <br />
+ <p>This step can be omitted in case that the Web Intents enabled mDNS device attaches a TXT answer with the previous answer.
+ </li>
+ <br />
+ <li>
+ For each matching response, i.e. the response TXT record does not have an action parameter or does have an <code>action</code> parameter matching the Action of the invoked intent,
+ send a unicast request with a SRV query of the webintens service instance.
+ <br />
+ <p>This step can be omitted in case that the Web Intents enabled mDNS device attaches a SRV answer with the previous answer.
+ </li>
+ <br />
+ <li>
+ For each response, send a unicast A and/or AAAA query of the host name in the SRV answer.
+ <br />
+ <p>This step can be omitted in case that the Web Intents enabled mDNS device attaches an A and/or AAAA answer with the previous answer.
+ </li>
+ <br />
+ <li>
+ The <a>mDNS enabled User Agent</a> attempts to retrieve the Web Intents document from the discovered <a>Web Intents enabled mDNS device</a>.
+ The destination URL consists of an IP address in the A or AAAA answer, a port number in the SRV record and an absolute path in the <code>location</code> parameter of the TXT record.
+ <br /> <br />
+ If the <a>mDNS enabled User Agent</a> fails to retrieve the Web Intents document it silently disregards the received response.
+ <br /> <br />
+ If the <code>action</code> parameter is present and does not match the <code>action</code> attributes of the Services registered in the retrieved Web Intents
+ document the <a>mDNS enabled User Agent</a> silently disregards the the received response.
+ <br /> <br />
+ Note that following steps are identical to those of UPnP described in 4.2.
+ </li>
+ <br />
+ <li>
+ It is expected that the Web Intents document contains registration markup and the <a>mDNS enabled User Agent</a> interprets this
+ registration markup according to the rules for registration defined by [[!WEBINTENTS]] and register the Services accordingly.
+ </li>
+ <br />
+ <li>
+ The <a>mDNS enabled User Agent</a> makes each dynamically registered Service, that matches the Action of the invoked intent, available for selection
+ by the user, typically by making them visible and selectable in a Web Intents Service picker.
+ </li>
+ <br />
+ <li>
+ Based on user selection of a dynamically registered Service the <a>mDNS enabled User Agent</a> loads the
+ Service handler code as defined by the <code>href</code> attribute in the registration markup for this Service according to the rules for
+ loading Service pages defined in [[!WEBINTENTS]].
+ </li>
+
+ </ol>
+
+ </section>
+
+ </section>
+ <section class="informative">
+ <h3>Sample Records</h3>
+
+ <p>
+ See below for the example records for Web Intents. An <a>mDNS enabled User Agent</a> looking for devices supporting http://webintents.org/view Web Intents can understand that
+ it is possible to get a Web Intents document for "LivingRoomTV" at http://192.168.1.47:3619/webintents.html.
+ </p>
+
+ <ul>
+ <li>
+ <code>_webintents._tcp.local. 120 IN PTR LivingRoomTV._webintents._tcp.local.</code>: A LivingRoomTV instance serves webintents service.
+ </li>
+ <li>
+ <code>LivingRoomTV._webintents._tcp.local. 120 IN SRV 0 0 3619 TV40EX-W2000.local.</code>: A host "TV40EX-W2000" in the link local network offers the LivingRoomTV webintents service instance in its port 3619.
+ </li>
+ <li>
+ <code>LivingRoomTV._webintents._tcp.local. 120 IN TXT location=/webintents.html action=http://webintents.org/view</code>: It offers http://webintents.org/view type of Web Intents. The absolete path for its Web Intents document is "/webintents.html". Note that the actual binary format of the TXT record value is concatinating key-value pairs each of which is a single byte length followed by 0-255 length key=value character string as defined in [DNS-SD].
+ </li>
+ <li>
+ <code>TV40EX-W2000 120 IN A 192.168.1.47</code>: A host "TV40EX-W2000" is on 192.168.1.47.
+ </li>
+ </ul>
+
+ </section>
+
+ </section>
+
+
+ <section class='informative'>
+ <h2>APIs / protocols Client - Service </h2>
+ <p>
+ The APIs / protocols for interaction between Client and Service pages are not defined by this specification. It is assumed that Web Intents
+ based APIs and protocols will be standardized by W3C and that these will be applicable for Client and Service applications running on User Agents that
+ comply to this specification. Different use cases will require different ways of interaction patterns between Client and Service.
+ </p>
+
+ <p>
+ Examples:
+ </p>
+ <ul>
+ <li>
+ A Client application invoking a "View" intent provides, as intent payload data, a link to a video to be displayed at the remote <a>Web Intents enabled UPnP device</a>.
+ The Service application takes full control of the video playback by providing control buttons and sends UPnP commands to the remote device.
+ So in this case there the simple "API" just gives the link to the video to play.
+ </li>
+ <li>
+ Some use cases require a longer lasting relation between the Client and Service applications. By using the MessagePort[] attribute of the intent object
+ a message channel can be established between the Client and Service page. This message channel can be used to run Service specific protocols,
+ for example a protocol that allows the Client application to send simple video playback control commands to a Service application.
+ </li>
+ </ul>
+
+ </section>
+
+ <section class='informative appendix'>
+ <h2>Examples and scenarios</h2>
+ <section>
+ <h3>View and control video on remote device through Service page control buttons</h3>
+ <p>
+ The following scenario describes how a Client page uses Web Intents to discover a remote video view service. The Service page
+ contains the UI for controlling the video playback.
+ </p>
+
+ <p align="left"><img src="Example_scenario_1/Slide1.png" alt="Example scenario 1/Slide1" width="700" height="700" ><br>
+ (<a href="Example_scenario_1/Slide1.png">View as PNG</a>)
+ </p>
+
+ <p align="left"><img src="Example_scenario_1/Slide2.png" alt="Example scenario 1/Slide2" width="700" height="700" ><br>
+ (<a href="Example_scenario_1/Slide2.png">View as PNG</a>)
+ </p>
+
+ <p align="left"><img src="Example_scenario_1/Slide3.png" alt="Example scenario 1/Slide3" width="700" height="700" ><br>
+ (<a href="Example_scenario_1/Slide3.png">View as PNG</a>)
+ </p>
+ </section>
+
+ <section>
+ <h3>View and control video on remote device through Client page control buttons</h3>
+ <p>
+ The following scenario describes how a Client page uses Web Intents to discover a remote video view service. The UI stays in the Client page,
+ which contains the UI controls for the video playback. This means that there is a need for continuous communication between the Client page and the Service page,
+ which is "hidden", i.e. it has no UI. The Client page creates a messaging channel and sends the messaging channel port to the Service page trhrough the intent invocation.
+ A high level "TV control" protocol, supporting commands such as "play", "pause" and "stop, runs on top of the messaging channel.
+ </p>
+ <p>
+ In this example the assumption is that he Client invokes an intent to discover a Service that supports a specified protocol running on top of the message channel So the
+ "discover" intent Action is used and Type is set to the specific protocol used to communicate with the Service.
+ </p>
+
+ <p class="issue">
+ This scenario assumes the possibility to have hidden/background Service pages or Service pages that are visible inline the Client page.
+ Currently [[!WEBINTENTS]] does not allow this but W3C DAP Action http://www.w3.org/2009/dap/track/actions/519 should add a proposal for a hidden disposition.
+ </p>
+
+ <p align="left"><img src="Example_scenario_2/Slide1.png" alt="Example scenario 2/Slide1" width="700" height="700" ><br>
+ (<a href="Example_scenario_2/Slide1.png">View as PNG</a>)
+ </p>
+
+ <p align="left"><img src="Example_scenario_2/Slide2.png" alt="Example scenario 2/Slide2" width="700" height="700" ><br>
+ (<a href="Example_scenario_2/Slide2.png">View as PNG</a>)
+ </p>
+
+ <p align="left"><img src="Example_scenario_2/Slide3.png" alt="Example scenario 2/Slide3" width="700" height="700" ><br>
+ (<a href="Example_scenario_2/Slide3.png">View as PNG</a>)
+ </p>
+
+ <p align="left"><img src="Example_scenario_2/Slide4.png" alt="Example scenario 2/Slide4" width="700" height="700" ><br>
+ (<a href="Example_scenario_2/Slide4.png">View as PNG</a>)
+ </p>
+ </section>
+
+
+
+ <section>
+ <h3>Example of Web Intents document</h3>
+
+ <p align="left"><img src="Example1_registration_page/Slide1.png" alt="Example1 registration page" width="280" height="280" ><br>
+ (<a href="Example1_registration_page/Slide1.png">View as PNG</a>)
+ </p>
+ </section>
+
+ <section>
+ <h3>Example of UPnP Device description document</h3>
+ <p align="left"><img src="Example_device_and_service_description_pages/Slide1.png" alt="Example device and service description pages/Slide1" width="600" height="600" ><br>
+ (<a href="Example_device_and_service_description_pages/Slide1.png">View as PNG</a>)
+ </p>
+ </section>
+
+ </section>
+
+ <section class='appendix'>
+ <h3>Acknowledgements</h3>
+ <p>
+ Many thanks to Sony colleagues Anders Isberg, Naoyuki Sato, Tatsuya Igarashi, Anders Edenbrandt and Björn Ekberg for all support.
+ <br /> <br />
+ Many thanks to Robin Berjon for making our lives so much easier with his cool specification editing tool.
+ </p>
+ </section>
+ </body>
+</html>
\ No newline at end of file