--- a/model/ProvenanceModel.html Fri Oct 07 19:57:56 2011 +0100
+++ b/model/ProvenanceModel.html Fri Oct 07 21:43:12 2011 +0100
@@ -247,7 +247,7 @@
<section id='preliminaries'>
<h2>Preliminaries</h2>
- <section>
+ <section id='conceptualization'>
<h3>A Conceptualization of the World</h3>
@@ -275,7 +275,7 @@
<ul>
<li>a report available at URL: fixes the nature of the thing, i.e. a document, and its location; </li>
<li>the version of the report available there today: fixes its version number, contents, and its date;</li>
-<li>the report independent of where it is hosted and of its content over time: fixes the nature of the thing as a concepual artifact.</li></ul>
+<li>the report independent of where it is hosted and of its content over time: fixes the nature of the thing as a conceptual artifact.</li></ul>
The provenance of these three characterized things will differ, and may be along the follow lines:
<ul>
<li>the provenance of a report available at URL may include: the act of publishing it and making it available at a given location, possibly under some license and access control;</li>
@@ -2497,9 +2497,76 @@
</section>
- </section>
+</section>
</section>
+<section id="resource-section">
+<h2>Resource, URIs, Entities, Identifiers, and Scope</h2>
+
+<p>This specification introduces the notion of an identifiable characterized thing in the world. In PROV-DM, an entity expression is a representation of such an identifiable characterized thing. An entity expression includes an identifier identifying this characterized thing. Identifiers are URIs (TBC). </p>
+
+<p>The term 'resource' is used in a general sense
+ for whatever might be identified by a URI [[!RFC3986]]. On the Web, a URI denotes a resource, without any expectation that the resource is accessed. </p>
+
+<p>The purpose of this section is to clarify the relationship between resource and the notions of characterized thing and entity expression. </p>
+
+<p>A resource is an instance of a thing in the world. One may take multiple perspectives on such a thing and its situation in the world, fixing some its aspects.</p>
+
+<p> We refer to the example of section <a href="#conceptualization">2.1</a> for a resource (at some URL) and three different perspectives, referred to as characterized things. Three different entity expressions can be expressed for this report, which in the PROV-ASN sample below, are expressed within a same account.
+</p>
+
+<pre>
+account(acc1,
+ http://example.org/asserter1,
+
+ entity(urn:demo:0, [ type="Document", location="http://example.org/crime.txt" ])
+ entity(urn:demo:1, [ type="Document", location="http://example.org/crime.txt", version="2.1", content="...", date="2011-10-07" ])
+ entity(urn:demo:2, [ type="Document", author="John" ])
+ ...)
+</pre>
+
+<p>Each entity expression contains an idenfier that identifies the characterized thing it represents.
+In this example, three identifiers were minted using the URN syntax with "demo" namespace.</p>
+
+<p>Given that the report is a resource denoted by the URI <span class="name">http://example.org/crime.txt</span>, we could simply use this URI as the identifier of an entity. This would avoid us minting new URIs. Hence, the report URI would play a double role: as a URI it denotes a resource accessible at that URI, and as a PROV-DM identifier, it identifies a specific characterization of this report. A given identifier identifies a single characterized thing within the scope of an account. Hence, below, all entities expressions have been given the same identifier but appear in the scope of different accounts. </p>
+
+<pre>
+account(acc2,
+ http://example.org/asserter1,
+
+ entity(http://example.org/crime.txt, [ type="Document", location="http://example.org/crime.txt" ])
+ ...)
+
+account(acc3,
+ http://example.org/asserter1,
+
+ entity(http://example.org/crime.txt, [ type="Document", location="http://example.org/crime.txt", version="2.1", content="...", date="2011-10-07" ])
+ ...)
+
+account(acc4,
+ http://example.org/asserter1,
+ entity(http://example.org/crime.txt, [ type="Document", author="John" ])
+ ...)
+</pre>
+
+<p>In this case, the URI <span class="name">http://example.org/crime.txt</span> still denotes the same resource; however, it identifies a different entity in each account. </p>
+
+<p> Alternatively, if we need to assert the existence of two different characterizations of the report within the same account, then alternate identifiers MUST be used, one of them being allowed to be the resource URI.</p>
+
+<pre>
+account(acc5,
+ http://example.org/asserter1,
+
+ entity(http://example.org/crime.txt, [ type="Document", location="http://example.org/crime.txt" ])
+ entity(urn:demo:1, [ type="Document", location="http://example.org/crime.txt", version="2.1", content="...", date="2011-10-07" ])
+
+ ...)
+
+</pre>
+
+
+</section>
+
<section class="appendix">
<h2>Illustration Conventions</h2>