Theories of Semantics on theWeb - Social Semantics: The Search for Meaning on the Web - page 84

single thing, like the Eiffel Tower or the concept of a unicorn. This viewpoint is
the one generally held by many Web architects, like Berners-Lee, who imagine it
holds not just for the Semantic Web, but the entire Web. The second position, which
we call the logicist position due to its more clear roots in non-modal logic, is that
for the Semantic Web, the meaning of a URI is given by whatever things satisfy
the model(s) given by the formal semantics of the Semantic Web. Adherents of this
position hold that the referent of a URI is ambiguous, as many different things can
satisfy whatever model is given by the interpretation of some sets of sentences using
the URI. This position is generally held by logicians, who claim that the Semantic
Web is entirely distinct from the hypertext Web, with URIs serving as nothing more
than particularly funny symbols.
These two antagonistic positions were subterranean in the development of the
Semantic Web, until a critical point was reached in an argument between Pat Hayes,
the AI researcher primarily responsible for the formal semantics of the Semantic
Web, and Berners-Lee. This argument was provoked by an issue called 'Social
Meaning and RDF' and was brought about by the following draft statement in
the RDF Concepts and Abstract Syntax Recommendation , “the meaning of an RDF
document includes the social meaning, the formal meaning, and the social meaning
of the formal entailments” so that “when an RDF graph is asserted in the Web,
its publisher is saying something about their view of the world” and “such an
assertion should be understood to carry the same social import and responsibilities
as an assertion in any other format” (2004). During the period of comments for the
RDF Working Drafts, Bijan Parsia commented that the above-mentioned sentences
do not “really specify anything and thus can be ignored” or are “dangerously
underthought and underspecified” and so should be removed (Parsia 2003). While at
first these sentences about the meaning of RDF seemed to be rather harmless and in
concordance with commonsense, the repercussions on the actual implementation
of the Semantic Web are surprisingly large, since “an RDF graph may contain
'defining information' that is opaque to logical reasoners. This information may be
used by human interpreters of RDF information, or programmers writing software
to perform specialized forms of deduction in the Semantic Web” (Klyne and Carroll
2004). In other words, a special type of non-logical reasoning can therefore be used
by the Semantic Web.
An example of this extra-logical reasoning engendered by the fact that URIs
identify 'one thing' is as follows. Assume that a human agent has found a URI for
the Eiffel Tower from DBpedia, and so by accessing the URI a Semantic Web agent
can discover a number of facts about the Eiffel Tower, such as that it is in Paris and
that its architect is Gustave Eiffel, and these statements are accessed as an RDF
graph (Auer et al. 2007). However, a human can have considerable background
knowledge about the Eiffel Tower, such as a vague belief that at some point in
time it was the tallest building in the world. This information is confirmed by the
human agent employing the follow-your-nose algorithm, where by following the
subject of any triple, the human would be redirected to the hypertext Wikipedia
article about the Eiffel Tower, where the agent discovers via a human-readable
description that the Eiffel Tower was in fact the tallest building until 1930, when