--- a/rdf-dataset/index.html Mon Dec 16 00:43:03 2013 +0100
+++ b/rdf-dataset/index.html Mon Dec 16 01:48:33 2013 +0100
@@ -125,10 +125,12 @@
<p>The <a href="http://www.w3.org/TR/rdf11-concepts/">Resource Description Framework (RDF)</a> version 1.1 defines the concept of RDF datasets, a notion introduced first by the SPARQL specification [[RDF-SPARQL-QUERY]]. An RDF dataset is defined as a collection of <a href="http://www.w3.org/TR/rdf11-concepts/#dfn-rdf-graph" title="RDF graph">RDF graphs</a> where all but one are <a href="http://www.w3.org/TR/rdf11-concepts/#dfn-named-graph" title="named graph">named graphs</a> associated with an <a href="http://www.w3.org/TR/rdf11-concepts/#dfn-iri">IRI</a> or <a href="http://www.w3.org/TR/rdf11-concepts/#dfn-blank-node">blank node</a> (the <a href="http://www.w3.org/TR/rdf11-concepts/#dfn-graph-name">graph name</a>), and the unnamed default graph [[RDF11-CONCEPTS]]. Given that RDF is a data model equipped with a formal semantics [[RDF11-MT]], it is natural to try and define what the semantics of datasets should be.</p>
- <p>The RDF Working Group was initially chartered to provide such semantics in its recommendation:</p>
- <blockquote cite="http://www.w3.org/2011/01/rdf-wg-charter">
+ <p>The RDF Working Group was <a href="http://www.w3.org/2011/01/rdf-wg-charter"">chartered</a>
+ to provide such semantics in its recommendation:</p>
+ <blockquote>
<h5>Required features</h5>
- <ul><li id="ng">Standardize a model and semantics for multiple graphs and graphs stores [...]</li></ul>
+ <ul><li id="ng">Standardize a model and semantics for multiple graphs and graphs stores
+ [...]</li></ul>
</blockquote>
<p>However, discussions within the Working Group revealed that very different assumptions currently exist among practitioners, who are using RDF datasets with their own intuition of the meaning of datasets. Defining the semantics of RDF datasets requires an understanding of the two following issues:</p>
@@ -171,7 +173,7 @@
<p>We first take a look at existing specifications that could shed a light on how the semantics of datasets should be defined. There are three important documents that closely relate to the issue:</p>
<ul>
<li>the RDF semantics, as standardized in 2004 [[RDF-MT]] and its revision in 2013 [[RDF11-MT]];</li>
- <li>the article <i>Named Graphs</i> by Carroll et al. [[NAMED-GRAPHS]], which first introduced the term “named graph” and contains a section on formal semantics;</li>
+ <li>the article <i>Named Graphs</i> by Carroll et al. [[CARROLL-05]], which first introduced the term “named graph” and contains a section on formal semantics;</li>
<li>the SPARQL specification [[RDF-SPARQL-QUERY]], which defines RDF datasets and how to query them.</li>
</ul>
@@ -189,7 +191,7 @@
<section id="sec-named-graph-paper">
<h3 id="named-graph">The Named Graphs paper</h3>
- <p>In Carroll et al. [[NAMED-GRAPHS]], a named graph is defined as a pair comprising an IRI and an RDF graph. The notion of RDF interpretation is extended to named graphs by saying that the graph IRI in the pair must denote the pair itself. This non-ambiguously answers the question of what the graph IRI denotes. This can then be used to define proper dataset semantics, as shown in Section 3.3. Note that it is deliberate that the graph IRI is forced to denote the pair rather than the RDF graph. This is done in order to differentiate two occurrences of the same RDF graph that could have been published at different times, or authored by different people. A simple reference to the RDF graph would simply identify a mathematical set, which is the same wherever it occurs.</p>
+ <p>In Carroll et al. [[CARROLL-05]], a named graph is defined as a pair comprising an IRI and an RDF graph. The notion of RDF interpretation is extended to named graphs by saying that the graph IRI in the pair must denote the pair itself. This non-ambiguously answers the question of what the graph IRI denotes. This can then be used to define proper dataset semantics, as shown in Section 3.3. Note that it is deliberate that the graph IRI is forced to denote the pair rather than the RDF graph. This is done in order to differentiate two occurrences of the same RDF graph that could have been published at different times, or authored by different people. A simple reference to the RDF graph would simply identify a mathematical set, which is the same wherever it occurs.</p>
</section>
<section id="sec-sparql">
@@ -214,7 +216,7 @@
<li>they define notions of interpretation and entailment in function of the corresponding notions in RDF Semantics.</li>
</ul>
- <p>The first item above reflects the indication given in [[RDF11-MT]] with respect to dataset semantics: <q cite="http://www.w3.org/TR/rdf11-mt/#rdf-datasets">a dataset SHOULD be understood to have at least the same content as its default graph</q>.</p>
+ <p>The first item above reflects the indication given in [[RDF11-MT]] (Section <a href="http://www.w3.org/TR/rdf11-mt/#rdf-datasets">"RDF Datasets"</a>) with respect to dataset semantics: <q>a dataset SHOULD be understood to have at least the same content as its default graph</q>.</p>
<p>The dependency on RDF semantics is such that most of the dataset semantics below reuse RDF semantics as a black box. More precisely, it is not necessary to be specific about how truth of RDF graphs is defined as long as there is a notion of interpretation that determines the truth of a set of triples. In fact, RDF Semantics does not define a single formal semantics, but multiple ones, depending on what standard vocabularies are endorsed by an application (such as the RDF, RDFS, XSD vocabularies). Consequently, we parameterize most of the definitions below with an unspecified entailment regime <var>E</var>. RDF 1.1 defines the following entailment regimes: simple entailment, D-entailment, RDF-entailment, RDFS-entailment. Additionally, OWL defines two other entailment regimes, based on the OWL 2 direct semantics [[OWL2-DIRECT-SEMANTICS]] and the OWL 2 RDF-based semantics [[OWL2-RDF-BASED-SEMANTICS]].</p>
<p>For an entailment regime <var>E</var>, we will say <var>E</var>-interpretation, <var>E</var>-entailment, <var>E</var>-equivalence, <var>E</var>-consistency to describe the notions of interpretations, entailment, equivalence and consistency associated with the regime <var>E</var>. Similarly, we will use the terms dataset-interpretation, dataset-entailment, dataset-equivalence, dataset-consistency for the corresponding notions in dataset semantics.</p>
@@ -479,9 +481,6 @@
<p>Communication of the intended semantics could be performed in various ways, from having the author tell the consumers directly, to inventing a protocol for this. Use of the HTTP protocol and content negotiation could be a possible way too. Special syntactic markers in the concrete serialization of datasets could convey the intended meaning. All of those are solutions that do not follow current practices.</p>
</section>
-<section id="references">
-</section>
-
<section class="appendix informative" id="changes">
<h2>Changes</h2>
<ul>
@@ -492,8 +491,6 @@
</ul>
</section>
-
-
</body>
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