Theories of Semantics on theWeb - Social Semantics: The Search for Meaning on the Web - page 96

( , ) ( , )

would satisfy, as would .

However, there is no reason why these models could not be “God Forthcoming,”
things in the real world itself, albeit given in set-theoretic terms (Smith 1996). To
summarize Tarksi's remarkably successful programme, model-theoretic semantics
can produce a theory of truth that defines the semantics of a sentence in terms of
the use of a translation of the sentence into some formal language with a finite
number of axioms, then using compositionality to define the truth of complex
sentences in terms of basic sentences, and finally determining the truth of those
basic sentences in terms of what things in a model satisfy the extensions of the basic
sentences as given by the axioms. This work marks the high-point of the logical
programme, as all questions of meaning are reduced to questions about giving the
interpretation of a sentence in terms of a formal notion of truth. This notion of
truth is not restricted by the logical atomist's epistemology of elementary sense
data, but instead can range over any possible formal language and any possible
world. This victory is not without its costs, since while Tarski provides the best
account of the relationship between logical descriptions and the world by simply
removing all questions that cannot be phrased formally, formal semantics by itself
leaves unsolved the fundamental question about how natural language relates to our
experience of the world. Ignoring a problem does not make it go away. So when
confronted with this vexing problem, champions of formal semantics often revert
to the Russellian doctrine of direct acquaintance, thereby returning to the original
problems that caused Tarski to abandon epistemology.

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4.3.3 Logical Descriptions Unbound on the Web

While the descriptivist theory of reference seems distant from the Identity Crisis
of the Web, it is in fact central to the position of Hayes and the Semantic Web as
a whole. This is primarily because Hayes's background was in formal logic, with
his particular specialty being the creation of Tarski-style semantics for knowledge
representation languages. What Hayes calls the “basic results in twentieth century
linguistic semantics” that Berners-Lee's dictum that “URIs identify one thing”
violates is the interpretation of URIs in a Tarski-style formal semantics (Hayes
2003a). For the logicist position, the semantics in the Semantic Web derive from the
Tarski-style formal semantics Hayes created for the Semantic Web (Hayes 2004).
Before delving into the formal semantics of RDF, it should be noticed that
these semantics are done by extension, like most other formal languages (Hayes
2004). However, the semantics of RDF are purposefully quite weak (they do not
allow arithmetic or constructs like the negation of a class), and so RDF avoids
logical paradoxes like the encoding of Godel sentences. Yet in order to make
RDF triples as flexible as possible, RDF includes features normally associated with
higher-order logic such as “a property may be applied to itself” and classes “may
contain themselves” (Hayes 2004). This is handled semantically by having first an