Database Reference
In-Depth Information
PREFIX
foaf:<
http://xmlns.com/foaf/0.1/
>
SELECT
?name?email
WHERE
{
?personafoaf:Person.
?personfoaf:name?name.
?personfoaf:mbox?email.
}
Figure 12.7.
Simple SPARQL Example
An RDF stream is identified by an IRI, which provides the location of
the data source. An example SPARQL stream query is provided in
Fig-
ure 12.8
whichillustrates a query that obtains all wind-speed observation
values greater than some threshold (e.g., 10) in the last 5 hours, from the
sensors
virtual rdf stream
swissex:WannengratWindSensors.srdf
.
Figure 12.8.
SPARQL Stream Example
4.2.3 Linked Data.
Realization of the Semantic-Web vision
has indeed faced challenges on multiple fronts, some impediments in-
cluding having to define and develop ontologies that domain experts
and representatives can agree upon, ensuring that data on the Web is
indeed marked up in semantic formats, etc. The
Linked Data
vision
