--- a/rdf-primer/index.html Tue Dec 03 15:33:20 2013 +0100
+++ b/rdf-primer/index.html Tue Dec 03 16:12:47 2013 +0100
@@ -228,7 +228,7 @@
descriptions of people
across multiple web sites.</li>
<li>Providing a standard-compliant way for exchanging data
- between graph databases.</li>
+ between RDF databases.</li>
<li>Interlinking various datasets within an organisation,
enabling cross-dataset queries to
be performed using SPARQL [[!SPARQL11-OVERVIEW]].</li>
@@ -250,16 +250,17 @@
<pre>
<subject> <predicate> <object>
</pre>
-
+
+ <!--
<p>The <strong>subject</strong> represents the resource we like to
make a statement about. The <strong>predicate</strong> represents
a property of the subject. The
<strong>object</strong> represents a value of the property
for this subject. Because RDF statements consist of three elements they are called
<strong>triples</strong>.</p>
-
- <p class="issue"><em>Alternative phrasing of the previous paragraph:</em>
- An RDF statement represents a relationship between two resources.
+ -->
+
+ <p>An RDF statement represents a relationship between two resources.
The <strong>subject</strong> and the <strong>object</strong>
represent the two resources being
related; the <strong>predicate</strong> represents the nature of their
@@ -321,7 +322,7 @@
<p>The abbreviation IRI is short for "International Resource
Identifier". An <a href="http://www.w3.org/TR/rdf11-concepts/#section-IRIs">IRI</a>
- identifies a Web resource. The notionof IRI is a
+ identifies a Web resource. The notion of IRI is a
generalization of URI (Uniform Resource Identifier), allowing
non-ASCII characters to be used in the IRI character string. IRIs are specified
in RFC 3987 [[!RFC3987]].
@@ -344,15 +345,21 @@
<div class="example"><a href="http://data.europeana.eu/item/04802/243FA8618938F4117025F17A8B813C5F9AA4D619">http://data.europeana.eu/item/04802/243FA8618938F4117025F17A8B813C5F9AA4D619</a></div>
+<!--
<figure>
<img src="example-graph-iris.jpg" width="75%"
alt="Informal graphs of the sample triples, with IRIs">
<figcaption>Informal graph of the sample triples, with IRIs</figcaption>
</figure>
+-->
<p class="note">RDF is agnostic about what the IRI stands for. However,
IRIs may be given meaning by particular vocabularies or
- conventions. RDF vocabularies are discussed in more detail in Sec.
+ 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 Sec.
<a href="#section-vocabulary">"RDF vocabularies"</a>. </p>
</section>
@@ -477,7 +484,7 @@
be adapted/removed in future versions.
</p>
- <p>Multiple graphs in a RDF document constitute an <a
+ <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
one default graph (i.e. without a name). The default graph
@@ -524,8 +531,8 @@
characteristics of
RDF data. For example, one can state that the IRI
<code>ex:friendOf</code> can be used as a property and that the
- subjects and objects of <code>ex:friendOf</code> triples must be resources of class
- </code>ex:Person</code>. <p>
+ subjects and objects of <code>ex:friendOf</code> triples must be
+ resources of class <code>ex:Person</code>. <p>
<p>RDF Schema uses the notion of <strong>class</strong> to
specify categories that can be used to classify resources. The
@@ -547,37 +554,37 @@
<th>Description</th>
</tr>
<tr>
- <td><em>Class</em> (a class)</td>
+ <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>
</tr>
<tr>
- <td><em>Property</em> (a class)</td>
+ <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>
</tr>
<tr>
- <td><em>type</em> (a property)</td>
+ <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> <striong>o</strong></td>
<td><strong>s</strong> (a resource) is an instance of <striong>o</strong> (a class)</td>
</tr>
<tr>
- <td><em>subClassOf</em> (a property)</td>
+ <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> <striong>o</strong></td>
<td><strong>s</strong> (a class) is a subclass of <striong>o</strong> (a class)</td>
</tr>
<tr>
- <td><em>subPropertyOf</em> (a property)</td>
+ <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> <striong>o</strong></td>
<td><strong>s</strong> (a property) is a sub-property of <striong>o</strong> (a property)</td>
</tr>
<tr>
- <td><em>domain</em> (a property)</td>
+ <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> <striong>o</strong></td>
<td>domain of <strong>s</strong> (a property) is <striong>o</strong> (a class)</td>
</tr>
<tr>
- <td><em>range</em> (a property)</td>
+ <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> <striong>o</strong></td>
<td>range of <strong>s</strong> (a property) is <striong>o</strong> (a class)</td>
</tr>
@@ -592,15 +599,15 @@
historical artefact, which is preserved for backward
compatibility.</p>
-<p>With the help of RDF Schema one can build a model of RDF data. A simple
-example:</p>
+<p>With the help of RDF Schema one can build a model of RDF data. A
+simple informal example:</p>
<pre class="example" id="rdfs-example">
- <Person> <type> <Class>
- <is a friend of> <type> <Property>
- <is a friend of> <domain> <Person>
- <is a friend of> <range> <Person>
- <is a good friend of> <subPropertyOf> <is a friend of>
+ <Person> <<strong>type</strong>> <Class>
+ <is a friend of> <<strong>type</strong>> <Property>
+ <is a friend of> <<strong>domain</strong>> <Person>
+ <is a friend of> <<strong>range</strong>> <Person>
+ <is a good friend of> <<strong>subPropertyOf</strong>> <is a friend of>
</pre>
<p>One of first RDF vocabularies used worldwide was the
@@ -626,7 +633,7 @@
<a href="http://www.w3.org/2006/03/wn/wn20/">RDF version</a>
available of WordNet 2.0, which was one
of the first elements of the <a href="http://linkeddata.org/">Linked
- Data Cloud</a>.</dd>
+ Data Cloud</a>. Similar databases exist for many other languages.</dd>
<dt><a href="http://www.w3.org/2004/02/skos/">SKOS</a></dt>
<dd>SKOS is a vocabulary for publishing classification schemes
@@ -662,8 +669,7 @@
N-Triples/N-Quads (line-based exchange formats) and RDF/XML. In
Appendix <a href="#section-other-syntaxes">"RDF syntax
examples"</a> the reader can find for each RDF syntax
- corresponding samples for the Turtle and TriG examples in this
- section. </p>
+ corresponding examples of the ones in this section. </p>
<section id="subsection-turtle">
@@ -675,7 +681,8 @@
support for namespaces, lists and shorthands for datatyped
literals. Turtle provides a trade-off between ease of
writing, ease of parsing and readability. Our
- <a href="#subsection-triple">first example</a> can be
+ <a href="#subsection-triple">first example</a> (in slightly
+ extended form) can be
represented in Turtle as follows:</p>
<pre class="example" id="turtle-example">
@@ -710,8 +717,8 @@
Lines 2-6 define IRI prefixes (such as <code>foaf:</code>), which can
be use for prefixed names (such as <code>foaf:Person</code>) instead of full IRIs.
The corresponding IRI is constructed by replacing the prefix with its
-corresponding IRI (in this example, <code>foaf:Person</code> stands for
-<code><http://xmlns.com/foaf/0.1/Person></code>). A period is used to
+corresponding IRI (in this example <code>foaf:Person</code> stands for
+<code><http://xmlns.com/foaf/0.1/Person></code>). A period is used to
signal the end of a Turtle statement. </p>
<p class="issue">
@@ -758,7 +765,7 @@
<p>In case of language-tagged strings the tag
appears directly after the string, separated by a <code>@</code>
-symbol, e.g. <code>"Leonard de Vinci"@fr</code>.</p>
+symbol, e.g. <code>"Léonard de Vinci"@fr</code>.</p>
<p class="note">For technical reasons the datatype of language-tagged
strings is not <code>xsd:string</code> but
@@ -779,7 +786,7 @@
<p>The term <code>_:x</code> is a blank node. It represents some
unamed tree depicted in the Mona Lisa painting and belonging to the
- "Ctpress" class. </p>
+"Cypress" class. </p>
<p>The above is by no means a full account of the Turtle syntax. For
more details about the syntax of Turtle the reader is referred to the
@@ -800,7 +807,7 @@
document. One could view it as one language. The names Turtle and TriG
still exist for historical reasons.</p>
- <p>The <a href="#subsection-multiple-graphs">multi-graph version of our example</a>
+ <p>The <a href="#subsection-multiple-graphs">multiple-graphs version of our example</a>
can be specified in TriG as follows:</p>
<pre class="example" id="trig-example">
@@ -872,21 +879,22 @@
for RDF data. These syntaxes were developed to cater for specific
application and/or usage needs. The examples given for each of
these syntaxes correspond to the same graph (i.e., the same set of
- triples) as the Turtle (single-graph, see <a
- href="#fig-abstract-graph-single">Fig. 4</a>) and
- TriG (multi-graph, see <a
- href="#fig-abstract-graph-multiple">Fig. 5</a>) examples. </p>
+ triples) as the Turtle example (in the case of a single graph, see <a
+ href="#fig-abstract-graph-single">Fig. 4</a>)or the TriG example
+ (in the case of multiple graphs, see <a
+ href="#fig-abstract-graph-multiple">Fig. 5</a>). </p>
<dl>
<dt>RDFa</dt>
<dd>RDFa [[RDFA-PRIMER]] (<a href="#rdfa-example">single-graph example</a>)
can be used to embed RDF data within
- HTML documents. This enables for example search engines to aggregate
- this data when crawling the web and use it to enrich search results, e.g.
+ HTML documents. This enables, for example, search engines to aggregate
+ this data when crawling the web and use it to enrich search
+ results (see, e.g.,
<a href="http://schema.org">schema.org</a>
and <a
href="https://support.google.com/webmasters/answer/99170?hl=en">Rich
- Snippets</a>.
+ Snippets</a>).
</dd>
<dt>JSON-LD</dt>
@@ -898,7 +906,7 @@
JSON objects, a mechanism in which a JSON document can refer to
an object described in another JSON document elsewhere on the
Web, as well as datatype and language handling. JSON-LD
- [[JSON-LD]] also provides a way to serialize RDF datasets
+ also provides a way to serialize RDF datasets
through the use of the <code>@graph</code> keyword. </dd>
<dt>N-Triples</dt>
@@ -935,8 +943,6 @@
<section id="section-semantics">
<h2>Semantics of RDF Graphs</h2>
-
- <p class="note">Optional section</p>
<p>RDF is grounded in a formal model-theoretic semantics which is
specified in the RDF
@@ -962,10 +968,12 @@
information about entailment regimes
please consult the RDF Semantics document [[RDF11-MT]]. </p>
+ <!--
<p class="note">As we saw in the earlier <a
href="#section-rurtle-example">Turtle example</a> (line 9) we could have
used the shorthand <code>ex:bob a foaf:Person</code> for the example
above. </p>
+ -->
<p>The semantics of RDF also tell us that the triple:</p>
<pre>
@@ -981,7 +989,7 @@
<p>Unlike many other data
modeling languages, RDF Schema allows considerble modelling
- freedomm. For example, the same entity may be used
+ freedom. For example, the same entity may be used
as both a class and a property. Also, there is no strict separation
between the world of "classes" and of "instances". Therefore, RDF
semantics views the following graph as valid:</p>
@@ -1030,7 +1038,7 @@
<a href="http://datahub.io/organization/lodcloud">datahub.io</a>.</p>
<P>A number of vocabulary terms have become popular for
- recording links between RDF data sources. A popular example is the
+ recording links between RDF data sources. An example is the
<code>sameAs</code> property provided by the OWL vocabulary. This
property can be used to indicate that two IRIs point in fact
to the same resource. This is useful because different publishers
@@ -1046,9 +1054,22 @@
<p>Such links can be deployed by RDF data-processing
software. </p>
+
+ </section>
+
+ <section id="section-conclusion">
+ <h2>More Information</p>
+
+ <p>This concludes our brief introduction into RDF. Please consult
+ the references to get more detailed information. You might also
+ want to take a look at the <a
+ href="http://www.w3.org/standards/semanticweb/data">W3C Linked Data page</a>. </p>
+
+ <p class="issue">Todo: check whther this is the right place to
+ point to in W3C space.</p>
</section>
-
+
<section id="section-other-syntaxes" class="appendix">
<h2>Examples of RDF syntaxes</h2>