--- a/drafts/rdf11-mt/Overview.html Wed Jul 03 09:31:56 2013 -0700
+++ b/drafts/rdf11-mt/Overview.html Wed Jul 03 09:33:37 2013 -0700
@@ -185,7 +185,7 @@
<h2 id="notation">Notation and Terminology</h2>
- <p>This document uses the following terminology for describing RDF graph syntax, all as defined in the companion RDF Concepts specification [[!RDF11-CONCEPTS]]: <em><a class="externalDFN" href="http://www.w3.org/TR/rdf11-concepts/#dfn-iri">IRI</a></em>, <em><a class="externalDFN" href="http://www.w3.org/TR/rdf11-concepts/#section-triples">RDF triple</a>, <a class="externalDFN" href="http://www.w3.org/TR/rdf11-concepts/#section-rdf-graph">RDF graph</a>, <a class="externalDFN" href="http://www.w3.org/TR/rdf11-concepts/#section-triples">subject</a>, <a class="externalDFN" href="http://www.w3.org/TR/rdf11-concepts/#section-triples" href="http://www.w3.org/TR/rdf11-concepts/#section-triples">predicate</a>, <a class="externalDFN" href="http://www.w3.org/TR/rdf11-concepts/#section-triples">object</a>, <a class="externalDFN" href="http://www.w3.org/TR/rdf11-concepts/#dfn-rdf-source">RDF source</a>, <a class="externalDFN" href="http://www.w3.org/TR/rdf11-concepts/#dfn-node">node</a>, <a class="externalDFN" href="http://www.w3.org/TR/rdf11-concepts/#dfn-blank-node">blank node</a>, <a class="externalDFN" href="http://www.w3.org/TR/rdf11-concepts/#dfn-literal">literal</a>, <a class="externalDFN" href="http://www.w3.org/TR/rdf11-concepts/#graph-isomorphism">isomorphic</a>, and <a class="externalDFN" href="http://www.w3.org/TR/rdf11-concepts/#section-dataset">RDF datasets</a>.</em> All the definitions in this document apply unchanged to <a class="externalDFN" href="http://www.w3.org/TR/rdf11-concepts/#section-generalized-rdf">generalized RDF triples, graphs, and datasets</a>. </p>
+ <p>This document uses the following terminology for describing RDF graph syntax, all as defined in the companion RDF Concepts specification [[!RDF11-CONCEPTS]]: <em><a class="externalDFN" href="http://www.w3.org/TR/rdf11-concepts/#dfn-iri">IRI</a></em>, <em><a class="externalDFN" href="http://www.w3.org/TR/rdf11-concepts/#section-triples">RDF triple</a>, <a class="externalDFN" href="http://www.w3.org/TR/rdf11-concepts/#section-rdf-graph">RDF graph</a>, <a class="externalDFN" href="http://www.w3.org/TR/rdf11-concepts/#section-triples">subject</a>, <a class="externalDFN" href="http://www.w3.org/TR/rdf11-concepts/#section-triples">predicate</a>, <a class="externalDFN" href="http://www.w3.org/TR/rdf11-concepts/#section-triples">object</a>, <a class="externalDFN" href="http://www.w3.org/TR/rdf11-concepts/#dfn-rdf-source">RDF source</a>, <a class="externalDFN" href="http://www.w3.org/TR/rdf11-concepts/#dfn-node">node</a>, <a class="externalDFN" href="http://www.w3.org/TR/rdf11-concepts/#dfn-blank-node">blank node</a>, <a class="externalDFN" href="http://www.w3.org/TR/rdf11-concepts/#dfn-literal">literal</a>, <a class="externalDFN" href="http://www.w3.org/TR/rdf11-concepts/#graph-isomorphism">isomorphic</a>, and <a class="externalDFN" href="http://www.w3.org/TR/rdf11-concepts/#section-dataset">RDF datasets</a>.</em> All the definitions in this document apply unchanged to <a class="externalDFN" href="http://www.w3.org/TR/rdf11-concepts/#section-generalized-rdf">generalized RDF triples, graphs, and datasets</a>. </p>
<p>The words <dfn>denotes</dfn> and <dfn>refers to</dfn> are used interchangeably as synonyms for the relationship between an IRI or literal and what it refers to in a given interpretation, itself called the <dfn>referent</dfn> or <dfn>denotation</dfn>. IRI meanings may also be determined by other constraints external to the RDF semantics; when we wish to refer to such an externally defined naming relationship, we will use the word <dfn>identify</dfn> and its cognates. For example, the fact that the IRI <code>http://www.w3.org/2001/XMLSchema#decimal</code> is widely used as the name of a datatype described in the XML Schema document [[XMLSCHEMA11-2]] might be described by saying that the IRI <em>identifies</em> that datatype. If an IRI identifies something it may or may not refer to it in a given interpretation, depending on how the semantics is specified. For example, an IRI used as a graph name <a>identify</a>ing a named graph in an <a href="http://www.w3.org/TR/rdf11-concepts/#section-dataset" class="external">RDF dataset</a> may refer to something different from the graph it identifies. </p>
@@ -250,13 +250,13 @@
<p> RDF applications which manipulate concrete syntaxes for RDF which use blank node identifiers should take care to keep track of the identity of the blank nodes they identify. Blank node identifiers often have a local scope, so when RDF from different sources is combined, identifiers may have to be changed in order to avoid accidental conflation of distinct blank nodes.</p>
<p> For example, two documents may both use the blank node identifier "<code>_:x</code>" to identify a blank node, but unless these documents are in a shared identifier scope or are derived from a common source, the occurrences of "<code>_:x</code>" in one document will identify a different blank node than the one in the graph described by the other document. When graphs are formed by combining RDF from multiple sources, it may be necessary to <dfn>standardize</dfn> apart the blank node identifiers by replacing them by others which do not occur in the other document(s). For example, the two graphs represented by the following texts: </p>
<p><code>ex:a ex:p _:x . </code><br/><br/>
-<img src="RDF11SemanticsDiagrams/example1.jpg" /></p>
+<img src="RDF11SemanticsDiagrams/example1.jpg" alt="Graph 1" /></p>
<p><code>ex:b ex:q _:x . </code><br/><br/>
-<img src="RDF11SemanticsDiagrams/example2.jpg"></p>
+<img src="RDF11SemanticsDiagrams/example2.jpg" alt="Graph 2" ></p>
<p>contain four nodes. Their union would therefore also contain four nodes:</p>
-<p><img src="RDF11SemanticsDiagrams/example4.jpg"></p>
+<p><img src="RDF11SemanticsDiagrams/example4.jpg" alt="Union Graph"></p>
<p> However, the document formed by simply concatenating these textual surface representations: </p>
@@ -264,7 +264,7 @@
ex:b ex:q _:x .</code><br/></p>
<p>describes a graph containing three nodes:</p>
-<p><img src="RDF11SemanticsDiagrams/example3.jpg"></p>
+<p><img src="RDF11SemanticsDiagrams/example3.jpg" alt="Incorrect Union Graph"></p>
<p> since the two occurrences of the blank node identifier "<code>_:x</code>" occurring in a common identifier scope identify the same blank node. The four-node union of these two graphs is more properly described by a surface form such as:</p>
<p><code>ex:a ex:p _:x1 .<br/>
ex:b ex:q _:x2 .</code></p>
@@ -274,11 +274,11 @@
<p>It is possible for two or more graphs to share a blank node, for example if they are subgraphs of a single larger graph or derived from a common source. In this case, the union of a set of graphs preserves the identity of blank nodes shared between the graphs. In general, the union of a set of RDF graphs accurately represents the same semantic content as the graphs themselves, whether or not they share blank nodes. </p>
<p>A related operation, called <dfn>merging</dfn>, takes the union after forcing any shared blank nodes, which occur in more than one graph, to be distinct in each graph. The resulting graph is called the <dfn>merge</dfn>. The merge of subgraphs of a graph may be larger than the original graph. For example, the result of merging the two singleton subgraphs of the three-node graph</p>
-<p><img src="RDF11SemanticsDiagrams/example3.jpg"></p>
+<p><img src="RDF11SemanticsDiagrams/example3.jpg" alt="Three-node Graph"></p>
<p>is the four-node graph</p>
-<p><img src="RDF11SemanticsDiagrams/example4.jpg"></p>
+<p><img src="RDF11SemanticsDiagrams/example4.jpg" alt="Four-node Graph"></p>
<p>The union is always an instance of the merge. If graphs have no blank nodes in common, then their merge and union are identical. </p>
@@ -398,7 +398,7 @@
<section class="informative"><h3 id="shared_blank_nodes">Shared blank nodes (Informative)</h3>
<p> The semantics for blank nodes are stated in terms of the truth of a graph. However, when two (or more) graphs share a blank node, their meaning is not fully captured by treating them in isolation. For example, consider the overlapping graphs</p>
-<p><img src="RDF11SemanticsDiagrams/example5.jpg"></p>
+<p><img src="RDF11SemanticsDiagrams/example5.jpg" alt="Overlapping Graphs"></p>
<p> and an interpretation I over the universe {Alice, Bob, Monica, Ruth} with:<br/>
I(<code>ex:Alice</code>)=Alice, I(<code>ex:Bob</code>)=Bob, IEXT(I(<code>ex:hasChild</code>))={<Alice,Monica>,<Bob,Ruth> }<br/></p>
<p>Each of the inner graphs is true under this interpretation, but the two of them together is not, because the three-node graph says that Alice and Bob have a child together. In order to capture the full meaning of graphs sharing a blank node, it is necessary to consider the union graph containing all the triples which contain the blank node.</p>
@@ -505,7 +505,7 @@
<section><h2 id="datatypes">Literals and datatypes</h2>
<p class="changenote"> In the 2004 RDF 1.0 specification, datatype D-entailment was defined as a <a>semantic extension</a> of RDFS-entailment. Here it is defined as a direct extension to basic RDF. This is more in conformity with actual usage, where RDF with datatypes is widely used without the RDFS vocabulary. If there is a need to distinguish this from the 2004 RDF 1.0 terminology, the longer phrasing "simple D-entailment" or "simple datatype entailment" should be used rather than "D-entailment". </p>
-<p> Datatypes are <a title="identify">identified</a> by IRIs. Interpretations will vary according to which IRIs they recognize as denoting datatypes. We describe this using a parameter D on interpretations. where D is the set of <dfn>recognize</dfn><strong>d</strong> datatype IRIs. We assume that a recognized IRI <a title+"identify">identifies</a> a unique datatype wherever it occurs, and the semantics requires that it refers to this identified datatype. The exact mechanism by which an IRI <a title="identify">identifies</a> a datatype IRI is considered to be external to the semantics. RDF processors which are not able to determine which datatype is identifier by an IRI cannot <a>recognize</a> that IRI, and should treat any literals type with that IRI as unknown names. </p>
+<p> Datatypes are <a title="identify">identified</a> by IRIs. Interpretations will vary according to which IRIs they recognize as denoting datatypes. We describe this using a parameter D on interpretations. where D is the set of <dfn>recognize</dfn><strong>d</strong> datatype IRIs. We assume that a recognized IRI <a title="identify">identifies</a> a unique datatype wherever it occurs, and the semantics requires that it refers to this identified datatype. The exact mechanism by which an IRI <a title="identify">identifies</a> a datatype IRI is considered to be external to the semantics. RDF processors which are not able to determine which datatype is identifier by an IRI cannot <a>recognize</a> that IRI, and should treat any literals type with that IRI as unknown names. </p>
<p class="changenote">In the 2004 RDF 1.0 specification, the semantics of datatypes referred to datatype maps. The current treatment subsumes datatype maps into the interpretation mapping on recognized IRIs.</p>
@@ -669,7 +669,7 @@
<p>RDF entails recognizing {<code>xsd:integer</code>}</p>
-<code>ex:a ex:p _:x . <br/>
+<p><code>ex:a ex:p _:x . <br/>
_:x rdf:type xsd:integer . </code></p>
<p>In addition, the first RDF semantic condition justifies the following entailment pattern:</p>
@@ -702,7 +702,7 @@
ex:a ex:p "false"^^xsd:boolean .<br/>
ex:v rdf:type xsd:boolean .</code></p>
-together RDF entail</p>
+<p>together RDF entail</p>
<p><code>ex:a ex:p ex:v .</code></p>
@@ -938,7 +938,7 @@
<p>RDFS does not partition the universe into disjoint categories of classes, properties and individuals. Anything in the universe can be used as a class or as a property, or both, while retaining its status as an individual which may be in classes and have properties. Thus, RDFS permits classes which contain other classes, classes of properties, properties of classes, etc. As the axiomatic triples above illustrate, it also permits classes which contain themselves and properties which apply to themselves. A property of a class is not necessarily a property of its members, nor vice versa. </p>
<section class="informative">
-<h4 id="rdfs_literal_note">A note on rdfs:Literal (Informative)</h3>
+<h4 id="rdfs_literal_note">A note on rdfs:Literal (Informative)</h4>
<p>The class <code>rdfs:Literal</code> is not the class of literals, but rather that of literal values, which may also be referred to by IRIs. For example, LV does not contain the literal <code>"foodle"^^xsd:string</code> but it does contain the string "foodle".</p>
<p>A triple of the form</p>
@@ -966,7 +966,7 @@
<P>RDFS entailment holds for all the following patterns, which correspond closely to the RDFS semantic conditions:</p>
<div class="title">RDFS entailment patterns.</div>
-<table border="1" summary="RDFS-D entailment patterns">
+<table border="1">
<tbody>
<tr >
<th ></th>
@@ -1079,7 +1079,7 @@
<h2 id="appendices">Appendices</h2>
-<section class="appendix" class="informative"><h2 id="entailment_rules">Entailment rules (Informative)</h2>
+<section class="appendix,informative"><h2 id="entailment_rules">Entailment rules (Informative)</h2>
<p>(<em>This section is based on work described more fully in </em>[[HORST04]]<em>, </em>[[HORST05]]<em>, which should be consulted for technical details and proofs.</em>) </p>
<p> The RDF and RDFS entailment patterns listed in the above tables can be viewed as left-to-right rules which add the entailed conclusion to a graph. These rule sets can be used to check RDF (or RDFS) entailment between graphs S and E, by the following sequence of operations:</p>
@@ -1088,7 +1088,7 @@
3. Apply the RDF (or RDF and RDFS) inference patterns as rules, adding each conclusion to the graph, to exhaustion; that is, until they generate no new triples. <br/>
4. Determine if E has an instance which is a subset of the set, i.e. whether the enlarged set simply entails E.</p>
-This process is clearly <a>correct</a>, in that if it gives a positive result then indeed S does RDF (RDFS) entail E. It is not, however, <a>complete</a>: there are cases of S entailing E which are not detectable by this process. Examples include:</p>
+<p>This process is clearly <a>correct</a>, in that if it gives a positive result then indeed S does RDF (RDFS) entail E. It is not, however, <a>complete</a>: there are cases of S entailing E which are not detectable by this process. Examples include:</p>
<table border="1" >
<tbody>
@@ -1150,7 +1150,7 @@
ex:b ex:q "string"^^xsd:string .<br/>
"string"^^xsd:string rdf:type xsd:string .</code> by <a>GrdfD1</a></p>
-which is an instance (in generalized RDF) of the desired conclusion, above.</p>
+<p>which is an instance (in generalized RDF) of the desired conclusion, above.</p>
<p> The second example can be derived using the RDFS rules:</p>
<p><code>ex:a rdfs:subPropertyOf _:b .<br/>
_:b rdfs:domain ex:c .<br/>
@@ -1168,7 +1168,7 @@
4. Apply the rules <a>GrdfD1</a> and <a>rdfD2</a> (and the rules <a>rdfs1</a> through <a>rdfs13</a>), with D={<code>rdf:langString</code>, <code>xsd:string</code>), to the set in all possible ways, to exhaustion. </p>
<p>Then we have the completeness result:</p>
-<p class="fact">If S is RDF (RDFS) consistent, then S RDF entails (RDFS entails) E just when the <a>generalized RDF (RDFS) closure</a> of S towards E simply entails E.</em> </p>
+<p class="fact">If S is RDF (RDFS) consistent, then S RDF entails (RDFS entails) E just when the <a>generalized RDF (RDFS) closure</a> of S towards E simply entails E. </p>
<p>The closures are finite. The generation process is decidable and of polynomial complexity. Detecting simple entailment is NP-complete in general, but of low polynomial order when E contains no blank nodes. </p>
@@ -1519,7 +1519,7 @@
suggested by Christopher Menzel. The generalized RDF syntax used in Appendix A, and the example showing the need for it, were suggested by Herman ter Horst, who also proved completeness and complexity results for the rule sets. Jeremy Carroll first showed that simple entailment is NP-complete in general. Antoine Zimmerman suggested several simplifications and improvements to the proofs and presentation.</p>
<p>The RDF 1.1 editors acknowledge valuable contributions from Thomas Baker, Dan Brickley, Gavin Carothers, Jeremy Carroll, Pierre-Antoine Champin, Richard Cyganiak, Martin J. Dürst, Alex Hall, Steve Harris, Ivan Herman, Eric Prud'hommeaux, Andy Seaborne, David Wood and Antoine Zimmermann. </p>
-<p>This specification is a product of extended deliberations by <a href="http://www.w3.org/2000/09/dbwg/details?group=46168&public=1">members of the RDF Working Group</a>. It draws upon the earlier specification [[RDF-MT]], whose editor acknowledged valuable inputs from Jeremy Carroll, Dan Connolly, Jan Grant, R. V. Guha, Herman ter Horst, Graham Klyne, Ora Lassilla, Brian McBride, Sergey Melnick, Peter Patel-Schneider, Jos deRoo and Patrick Stickler.
+<p>This specification is a product of extended deliberations by <a href="http://www.w3.org/2000/09/dbwg/details?group=46168&public=1">members of the RDF Working Group</a>. It draws upon the earlier specification [[RDF-MT]], whose editor acknowledged valuable inputs from Jeremy Carroll, Dan Connolly, Jan Grant, R. V. Guha, Herman ter Horst, Graham Klyne, Ora Lassilla, Brian McBride, Sergey Melnick, Peter Patel-Schneider, Jos deRoo and Patrick Stickler.
</p>