Theories of Semantics on theWeb - Social Semantics: The Search for Meaning on the Web - page 85

it was superseded in height by New York City's Chrysler building. This information
is not explicitly in the RDF graphs provided. It is furthermore difficult to even
phrase this sort of temporal information in RDF. Furthermore, the human agent
discovers another URI for the Eiffel Tower, an RDF version of Wordnet in the
file synset-Eiffel Tower-noun-1.rdf (van Assem et al. 2006). When the
human agent accesses this URI, there is little information in the RDF graph except
that this URI is used for a noun. However, the human-readable gloss property
explains that the referent of this URI is 'a wrought iron tower 300 m high that was
constructed in Paris in 1889; for many years it was the tallest man-made structure.'
Therefore, the human agent believes that there is indeed a singular entity called
the 'Eiffel Tower' in Paris, and that this entity was in fact at some point the tallest
building in the world, and so the two URIs are equivalent in some sense, although
the URIs do not formally match. What the 'Social Meaning' clause was trying to
state is that the human should be able to non-logically infer that both URIs refer to
the Eiffel Tower in Paris, and they use this information to merge the RDF graphs,
resulting in perhaps some improved inferences in the future.
This use-case was put forward primarily by Berners-Lee, and the W3C RDF
Working Group decided that deciding on the relationship between the social and
formal meaning of RDF was beyond the scope of the RDF Working Group to decide,
so the RDF Working Group appealed to the W3C TAG for a decision. As TAG
member Connolly noticed, they “didn't see a way to specify how this works for RDF
without specifying how it works for the rest of the Web at the same time” (Berners-
Lee 2003b). In particular, Berners-Lee then put forward his own viewpoint that “a
single meaning is given to each URI,” which is summarized by the slogan that a URI
“identifies one thing” (2003c). In response, Hayes said that “it is simply untenable
to claim that all names identify one thing” (2003a). Furthermore, he goes on to state
that this is one of the basic results of the knowledge representation community and
twentieth century linguistic semantics, and so that the W3C cannot by fiat render the
judgment that a URI identifies one thing. Berners-Lee rejects Hayes's claim that the
Semantic Web must somehow build upon the results of logic and natural language,
instead claiming that “this system is different from natural language: we designed
it such that each URI identifies one and only one concrete thing in the real world or
one and only one globally shared concept” (2003a). At this point, in exasperation,
Hayes retorted that “I'm not saying that the 'unique identification' condition is an
unattainable ideal: I'm saying that it doesn't make sense, that it isn't true, and that
it could not possibly be true. I'm saying that it is crazy ” (2003b). While Hayes did
not explain his own position fully, as he was the editor of the formal semantics of
RDF and had the support of other logicians in the RDF Working Group, the issue
deadlocked and the RDF Working Group was unable to come to a consensus. In
order to move RDF from a Working Draft to a Recommendation, the W3C RDF
Working Group removed all references to social meaning from the RDF documents.
One should be worried when two prominent researchers such as Berners-Lee
and Hayes have such a titanic disagreement, where no sort of consensus agreement
seems forthcoming. Yet who is right? Berners-Lee's viewpoint seems intuitive and
easy to understand. However, from the standpoint of the formal semantics of logic,