--- a/rdf-primer/index.html Tue Jan 28 23:14:07 2014 +0100
+++ b/rdf-primer/index.html Wed Jan 29 01:53:54 2014 +0100
@@ -156,17 +156,13 @@
<p>In particular RDF can be used to publish and interlink data on the Web.
For example, retrieving <code>http://www.example.org/bob#me</code>
could provide data about Bob, including the fact that he
- knows Alice, as identified by her IRI.
+ knows Alice, as identified by her IRI (an IRI is an "International
+ Resource Identifier"; see <a href="#subsection-IRI">Sec. 3.2</a> for details).
Retrieving Alice's IRI could then provide more data about her, including links
to other datasets for her friends, interests, etc. A person or
an automated process can then follow such links and aggregate data about these
various things. Such uses of RDF are often
qualified as Linked Data [[LINKED-DATA]]. </p>
-
- <div class="note">
- An IRI is an "International Resource Identifier". See <a
- href="#subsection-IRI">Sec. 3.2</a> for details.
- </div>
<p>This document is not normative and does not give a complete
account of RDF 1.1. Normative
@@ -220,7 +216,7 @@
descriptions of people
across multiple Web sites.</li>
<li>Providing a standard-compliant way for exchanging data
- between RDF databases.</li>
+ between databases.</li>
<li>Interlinking various datasets within an organisation,
enabling cross-dataset queries to
be performed using SPARQL [[!SPARQL11-OVERVIEW]].</li>
@@ -344,14 +340,12 @@
<div class="example"><a href="http://data.europeana.eu/item/04802/243FA8618938F4117025F17A8B813C5F9AA4D619">http://data.europeana.eu/item/04802/243FA8618938F4117025F17A8B813C5F9AA4D619</a></div>
- <p class="note">RDF is agnostic about what the IRI represents. However,
+ <p>RDF is agnostic about what the IRI represents. However,
IRIs may be given meaning by particular vocabularies or
conventions. For example, <a
href="http://wiki.dbpedia.org/Datasets#h338-3">DBpedia</a> uses IRIs of the form
<code>http://dbpedia.org/resource/Name</code> to denote the thing
- described by the corresponding Wikipedia article.
- RDF vocabularies are discussed in more detail in
- <a href="#section-vocabulary">Sec. 4</a>. </p>
+ described by the corresponding Wikipedia article.</p>
</section>
@@ -402,8 +396,7 @@
we know to be a cypress tree. Resources without identifiers such as the
painting's cypress tree can be represented by <a
href="http://www.w3.org/TR/rdf11-concepts/#section-blank-nodes">"blank
- nodes"</a> in RDF. A blank node indicates an un-named
- thing. Blank nodes are like simple
+ nodes"</a> in RDF. Blank nodes are like simple
variables in algebra; they represent some thing without saying
what their value is.
</p>
@@ -423,11 +416,18 @@
<h3>Multiple graphs</h3>
<p>RDF provides a mechanism to group RDF statements in multiple
- graphs and associate each graph with an IRI. Multiple graphs in
+ graphs and associate each graph with an IRI . Multiple graphs are a recent extension of the RDF
+ data model. In practice, RDF tool builders and data managers
+ needed a mechanism to talk about subsets of of a collection of
+ triples. Multiple graphs were first introduced in the RDF query
+ language SPARQL. The RDF data model was therefore extended with a notion of
+ multiple graphs that is closely aligned with SPARQL.</p>
+
+ <p>Multiple graphs in
an RDF document constitute an
<a href="http://www.w3.org/TR/rdf11-concepts/#section-dataset">RDF
dataset</a>. An RDF dataset may have multiple named graphs and
- at most one default graph (i.e. a graph without a name). </p><p>
+ at most one unnamed ("default") graph. </p><p>
<p>For example, the
statements in the <a href="#subsection-triple">first example</a>
@@ -442,8 +442,8 @@
<Bob> <is interested in> <the Mona Lisa>.
</pre>
- <p class="note">The IRI associated with the graph is
- called the "graph name" in [[!RDF11-CONCEPTS]]. </p>
+ <p>The IRI associated with the graph is
+ called the "graph name" [[!RDF11-CONCEPTS]]. </p>
<p>A second graph could be provided by <a
href="http://www.wikidata.org/">Wikidata</a>
@@ -455,41 +455,32 @@
<The video 'La Joconde à Washington'> <is about> <the Mona Lisa>
</pre>
- <p>In the example default (unnamed) graph below we see two triples that
- have a graph name as subject: </p>
+ <p>Below is an example of an unnamed graph. It contains two triples that
+ have the graph name <code><http://example.org/bob></code>
+ as subject. The triples associate publisher and license information with the
+ this graph IRI: </p>
<pre>
<http://example.org/bob> <is published by> <http://example.org>.
<http://example.org/bob> <has license> <http://creativecommons.org/licenses/by/3.0/>.
</pre>
- <p>RDF 1.1 doesn't prescribe any specific semantics for
- datasets. Possible semantics are described in a separate note
- [[RDF11-DATASETS]]. In this example dataset we assume graph
+ <p> In this example dataset we assume graph
names represent the source of the RDF data held within the
corresponding graphs, i.e. by retrieving
<code><http://example.org/bob></code> we would get access to the four triples
- in that graph. In the example default graph we associate
- metadata (publisher and license information) with the
- <code><http://example.org/bob></code> graph.</p>
+ in that graph.</p>
<p class="note">RDF provides no way to convey this semantic
assumption (i.e., that graph names represent the source of the
RDF data) to other readers of the dataset. Those readers will
need to rely on out-of-band knowledge to interpret the dataset
- in the intended way. </p>
+ in the intended way. Possible semantics of datasets are described in a separate note
+ [[RDF11-DATASETS]]. </p>
<p><a href="#subsection-trig">Sec. 5.2</a> provides an example
of concrete syntax for this example.</p>
- <p class="note">Multiple graphs are a recent extension of the RDF
- data model. In practice, RDF tool builders and
- data managers needed a mechanism to talk about subsets of of a
- collection of
- triples. Multiple graphs were first introduced in the RDF query
- language SPARQL. The RDF data model was therefore extended with a notion of
- multiple graphs that is closely aligned with SPARQL. </p>
-
</section>
</section>
@@ -529,6 +520,7 @@
<table id="table-rdf-schema">
+ <caption>Table 1: RDF Schema Constructs</caption>
<tbody>
<tr>
<th>Construct</th>
@@ -537,38 +529,38 @@
</tr>
<tr>
<td><a href="http://www.w3.org/TR/rdf-schema/#ch_classes">Class</a> (a class)</td>
- <td><strong>s</strong> <code>rdf:type rdfs:Class</code></td>
- <td><strong>s</strong> (a resource) is an RDF class</td>
+ <td><strong>C</strong> <code>rdf:type rdfs:Class</code></td>
+ <td><strong>C</strong> (a resource) is an RDF class</td>
</tr>
<tr>
<td><a href="http://www.w3.org/TR/rdf-schema/#ch_property">Property</a> (a class)</td>
- <td><strong>p</strong> <code>rdf:type rdf:Property</code></td>
- <td><strong>p</strong> (a resource) is an RDF property</td>
+ <td><strong>P</strong> <code>rdf:type rdf:Property</code></td>
+ <td><strong>P</strong> (a resource) is an RDF property</td>
</tr>
<tr>
<td><a href="http://www.w3.org/TR/rdf-schema/#ch_type">type</a> (a property)</td>
- <td><strong>s</strong> <code>rdf:type</code> <strong>o</strong></td>
- <td><strong>s</strong> (a resource) is an instance of <strong>o</strong> (a class)</td>
+ <td><strong>I</strong> <code>rdf:type</code> <strong>C</strong></td>
+ <td><strong>I</strong> (a resource) is an instance of <strong>C</strong> (a class)</td>
</tr>
<tr>
<td><a href="http://www.w3.org/TR/rdf-schema/#ch_subclassof">subClassOf</a> (a property)</td>
- <td><strong>s</strong> <code>rdfs:subClassOf</code> <strong>o</strong></td>
- <td><strong>s</strong> (a class) is a subclass of <strong>o</strong> (a class)</td>
+ <td><strong>C1</strong> <code>rdfs:subClassOf</code> <strong>C2</strong></td>
+ <td><strong>C1</strong> (a class) is a subclass of <strong>C2</strong> (a class)</td>
</tr>
<tr>
<td><a href="http://www.w3.org/TR/rdf-schema/#ch_subpropertyof">subPropertyOf</a> (a property)</td>
- <td><strong>s</strong> <code>rdfs:subPropertyOf</code> <strong>o</strong></td>
- <td><strong>s</strong> (a property) is a sub-property of <strong>o</strong> (a property)</td>
+ <td><strong>P1</strong> <code>rdfs:subPropertyOf</code> <strong>P2</strong></td>
+ <td><strong>P1</strong> (a property) is a sub-property of <strong>P2</strong> (a property)</td>
</tr>
<tr>
<td><a href="http://www.w3.org/TR/rdf-schema/#ch_domain">domain</a> (a property)</td>
- <td><strong>s</strong> <code>rdfs:domain</code> <strong>o</strong></td>
- <td>domain of <strong>s</strong> (a property) is <strong>o</strong> (a class)</td>
+ <td><strong>P</strong> <code>rdfs:domain</code> <strong>C</strong></td>
+ <td>domain of <strong>P</strong> (a property) is <strong>C</strong> (a class)</td>
</tr>
<tr>
<td><a href="http://www.w3.org/TR/rdf-schema/#ch_range">range</a> (a property)</td>
- <td><strong>s</strong> <code>rdfs:range</code> <strong>o</strong></td>
- <td>range of <strong>s</strong> (a property) is <strong>o</strong> (a class)</td>
+ <td><strong>P</strong> <code>rdfs:range</code> <strong>C</strong></td>
+ <td>range of <strong>P</strong> (a property) is <strong>C</strong> (a class)</td>
</tr>
</tbody>
</table>
@@ -671,7 +663,7 @@
<p>Turtle [[TURTLE]] provides a syntax for RDF
graphs, which is relatively convenient for humans.
- In its basic form a triple in Turtle looks this:<P>:
+ In its basic form a triple in Turtle looks this:<P>
<pre class="example">
<http://example.org/bob#me> <http://xmlns.com/foaf/0.1/knows> <http://example.org/alice#me> .
@@ -734,8 +726,8 @@
should informally be read as "Bob (is) a Person". The
<code>a</code> predicate
is a shorthand for the property <code>rdf:type</code> which models the
-instance relation (see Table <a href="#table-rdf-schema">"RDF Schema
-constructs"</a>). The <code>a</code> shorthand is intended to match the human
+instance relation (see <a href="#table-rdf-schema">Table 1</a>).
+The <code>a</code> shorthand is intended to match the human
intuition about <code>rdf:type</code>. </p>
<p>In line 11 we see an example of a literal, in this case a date. The
@@ -756,8 +748,8 @@
<figcaption>Graph of the Turtle example</figcaption>
</figure>
-<P class="note">N-Triples is a line-based subset of Turtle, where each triple
-corresponds to one line. Check the <a
+<P class="note">N-Triples is a line-based subset of Turtle and is a
+useful vehicle to understand how concrete and abstract syntax are related. Check the <a
href="#subsection-ntriples">N-Triples example</a>
to see that each line represents precisely one triple of the graph above. </p>
</pre>