The Semantic Web - Social Semantics: The Search for Meaning on the Web - page 59

is called a graph , as illustrated in Fig. 3.3 by two triples having the same subject,
namely that 'The Eiffel Tower in Paris has as an architect called Gustave Eiffel.'
With the ability to make separate statements using URIs, the main purpose of
RDF is revealed to be information integration . Due to their reliance on URIs, RDF
graphs can graph merge ,when two formerly separate graphs combine with each
other when they use any of the same URIs . The central purpose of URIs is to allow
independent agents to make statements about the same referent. With a common
language of URIs, agents can merge information about the referents of the URIs in
a decentralized manner.

3.2.3 RDF and the Principle of Self-description

Once the Principle of Universality and the Principle of Linking are obeyed, the
Principle of Self-Description naturally follows, and RDF is no exception. Self-
description is a crucial advantage of RDF in decentralized environments, since an
agent by following links can discover the context of a triple needed for its interpreta-
tion. As witnessed by the Brachman and Smith survey of knowledge representation
systems, a bugbear of semantic networks was their inability to be transferred
outside of the closed domain and centralized research group that designed them
(Brachman and Smith 1980). The crucial context for usage of a particular semantic
network was always lost in transfer, so that what precisely “IS-A” means could vary
immensely between contexts, such as the difference between a sub-class relationship
or individual identity (Brachman 1983). By providing their own method of self-
description, RDF triples can be transported from one context to another, at least in
an ideal world where normal conditions, such as when the URIs in the triple can be
used to access a web-page describing its content, and correct media types are used.
The hypertext Web, when every resource is linked together, provides a seamless
space of linked documents. For example, the W3C tries to deploy its own internal
infrastructure in a manner compatible with the principles of Web architecture. Its
e-mail lists are archived to the Web, and each e-mail is given a URI, so an agent
may follow links seamlessly from one e-mail message to another, and by following
links can launch applications to send e-mail, discover more about the group, and
in new e-mails reference previous topics. Likewise, an initiative called “Linked
Data” attempts to deploy massive public data-sets as RDF, and its main tenet is
to follow the Principle of Self Description (Bizer et al. 2008). The hope is that
the Semantic Web can be thought of as a seamless web of linked data, so that
an agent can discover the interpretation of Semantic Web data by just following
links. These links will then go to more data which may host formal definitions or
informal natural language descriptions and multimedia depictions. For example,
if one finds an RDF triple such as ex:EiffelTower ex:hasArchitect
ex:Gustave Eiffel , one can discover more information about the Eiffel
Tower, like a picture of it or the fact that construction was finished in 1889, by
accessing http://www.example.org/EiffelTower .