Database Reference
In-Depth Information
The subject and predicate must be resources. This means that they
are things or concepts having a URI. The object however can be a re-
source or a literal (such as the string “USA” or the number “10”).
It is most helpful to perceive RDF as a graph, where subject resources
are represented in ovals, literals in rectangles, and predicate (relation-
ships) represented as directed edges between ovals or between ovals and
rectangles. An example is illustrated in
Figure 12.2
.
URI2#USA
URI1#Washington DC
URI4#City
618,000
Figure 12.2.
RDF as a Graph
The most popular representation for RDF is RDF/XML. In this case,
the RDF is represented in XML format, as illustrated in
Figure 12.3
,
where XML elements are used to capture the fundamental resources
and relationships in any RDF triple.
<rdf:Descriptionrdf:about=“URI1#WashingtonDC">
<rdf:typerdf:resource=“URI4#City"/>
<URI2#isCapitalOfrdf:resource=“URI3#USA"/>
</rdf:Description>
Figure 12.3.
RDF XML Representation
RDF(S) stands for RDF
(Schema)
[76]. This can be viewed as a meta-
model that is used to define the vocabulary used in an RDF document.
