humans to understand and applications to use. New reasoning services
can be used to alert developers to unanticipated and/or undesirable interactions when modules are integrated
and to identify a subset of the original
ontology that is indistinguishable from
it when used to reason about the relevant subset of the domain. 4
The availability of an SQL has been
an important factor in the success of
relational databases, and there have
been several proposals for a semantic
Web query language. As in the case of
RDF and OWL, the W3C in 2004 set up
a standardization working group that
in January 2008 completed its work
on the SPARQL query language standard ( www.w3.org/TR/rdf-sparql-que-
ry). Strictly speaking, this language is
only for RDF, but it is easy to see how
it could be extended for use with OWL
ontologies, something already happening in practice.
As I mentioned earlier, major research efforts have been directed toward tackling some of the barriers to
realizing the semantic Web; considerable progress has been made in such
areas as ontology alignment (
reconciling ontologies that describe overlapping domains), 18 ontology extraction
(extracting ontologies from text), 16 and
the automated annotation of both text6
5 Of particular interest is
the growth of Web 2.0 applications,
showing how it might be possible for
user communities to collaboratively
annotate Web content, as well as create simple forms of ontology via the development of hierarchically organized
sets of tags, or folksonomies. 21
Progress has also been made in developing
the infrastructure needed to add structured annotations to existing Web resources. For example, in October 2008
the W3C produced a Recommendation
for RDFa, a mechanism for embedding
RDF in existing XHTML documents
Semantic Web research aims to help
Web-accessible information and services be more effectively exploited, particularly by software agents and applications. As a first step, the W3C developed
new languages, including RDF and
OWL, that allow for the description of
Web resources and the representation
of knowledge to enable applications to
use resources more intelligently.
Although a wide range of semantic
Web applications is available today,
fully realizing the semantic Web still
seems a long way off and would first require the solution of many challenging
research problems, including those
in knowledge representation and reasoning, databases, computational linguistics, computer vision, and agent
systems. Moreover, most of the Web is
yet to be semantically annotated, and
relatively few ontologies are available
(even fewer high-quality ones).
However, semantic Web research
already has a major influence on the
development and deployment of ontology languages and tools (often called
semantic Web technologies). They
have become a de facto standard for
ontology development and are seeing
increased use in research labs, as well
as in large-scale IT projects, particularly those where the schema plays an
important role, where information
has high value, and where information
may be incomplete. This emerging role
is reflected in extended support for semantic Web technologies, including
commercial tools, implementations,
and applications, from commercial
vendors, including Hewlett-Packard,
IBM, Oracle, and Siemens.
Related challenges involve both expressive power and scalability. However, the success of the technologies also
motivates research and development
efforts in academic institutions and
industry to address these challenges; it
seems certain these efforts will have a
major influence on the future development of information technology.
I want to thank Uli Sattler of the University of Manchester and Franz Baader of
Dresden Technical University for letting me borrow the idea of using Harry
Potter in the ontology examples.
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Ian Horrocks ( firstname.lastname@example.org) is a
professor of computer science in the oxford university
computing Laboratory and a fellow of oriel college,