review by Guus
authorGuus Schreiber <>
Tue, 03 Dec 2013 16:12:47 +0100
changeset 1454 26abc7cad360
parent 1453 bd93e1482631
child 1455 dbd3845611d0
review by Guus
--- 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 @@
       &lt;subject&gt;  &lt;predicate&gt; &lt;object&gt;
+    <!--
     <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
-    <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="">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=""></a></div>
       <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>
     <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="">DBpedia</a>  uses IRIs of the form
+    <code></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>
@@ -477,7 +484,7 @@
       be adapted/removed in future versions. 
-      <p>Multiple graphs in a RDF document constitute an <a
+      <p>Multiple graphs in an RDF document constitute an <a
       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 @@
-      <td><em>Class</em> (a class)</td>
+      <td><a href="">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><em>Property</em> (a class)</td>
+      <td><a href="">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><em>type</em> (a property)</td>
+      <td><a href="">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>
-      <td><em>subClassOf</em> (a property)</td>
+      <td><a href="">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>
-      <td><em>subPropertyOf</em> (a property)</td>
+      <td><a href="">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>
-      <td><em>domain</em> (a property)</td>
+      <td><a href="">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>
-      <td><em>range</em> (a property)</td>
+      <td><a href="">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>
@@ -592,15 +599,15 @@
 historical artefact, which is preserved for backward
-<p>With the help of RDF Schema one can build a model of RDF data. A simple
+<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">
-  &lt;Person&gt; &lt;type&gt; &lt;Class&gt;
-  &lt;is a friend of&gt; &lt;type&gt; &lt;Property&gt;
-  &lt;is a friend of&gt; &lt;domain&gt; &lt;Person&gt;
-  &lt;is a friend of&gt; &lt;range&gt; &lt;Person&gt;
-  &lt;is a good friend of&gt; &lt;subPropertyOf&gt; &lt;is a friend of&gt;
+  &lt;Person&gt; &lt;<strong>type</strong>&gt; &lt;Class&gt;
+  &lt;is a friend of&gt; &lt;<strong>type</strong>&gt; &lt;Property&gt;
+  &lt;is a friend of&gt; &lt;<strong>domain</strong>&gt; &lt;Person&gt;
+  &lt;is a friend of&gt; &lt;<strong>range</strong>&gt; &lt;Person&gt;
+  &lt;is a good friend of&gt; &lt;<strong>subPropertyOf</strong>&gt; &lt;is a friend of&gt;
 <p>One of first RDF vocabularies used worldwide was the
@@ -626,7 +633,7 @@
   <a href="">RDF version</a>
   available of WordNet 2.0, which was one 
   of the first elements of the <a href="">Linked
-  Data Cloud</a>.</dd>
+  Data Cloud</a>. Similar databases exist for many other languages.</dd>
   <dt><a href="">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><></code>). A period is used to
+corresponding IRI (in this example <code>foaf:Person</code> stands for
+<code>&lt;;</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>"LĂ©onard 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>
       <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=""></a> 
       and <a
-      Snippets</a>. 
+      Snippets</a>). 
@@ -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>
@@ -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>
@@ -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=""></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="">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 id="section-other-syntaxes" class="appendix">
    <h2>Examples of RDF syntaxes</h2>