Notes on computational linguistics.pdf - UCLA Department of ...

Stabler - Lx 185/209 2003
16.2 Contextual influences
This is obvious with the various pronouns and tense markings found in human languages. A standard way to
deal with this is found in Tarski’s famous and readable treatment of expressions like p(X) in first order logic
(Tarski, 1935), and now in almost every introductory logic text. The basic idea is to think of each (declarative)
sentence itself as having a value which is a function from contexts to truth values.
We will postpone the discussion of pronouns and tenses, but we can extend the basic idea of distinguishing
the linguistic and non-linguistic components of the problem to a broad range of contextual influences. For
example, if in a typical situation I say George charge -s, I may expect you to understand a particular individual
by George, and I may expect you to figure out something about what I mean by charge. For example, George
could be a horse, and by charge I may mean run toward you. Or George could be a grocer, and I may mean that
he makes you pay for your food. This kind of making sense of what an utterance means is clearly something
that goes on when we understand fluent language, but it is regarded as non-linguistic because the process
apparently involves general, non-linguistic knowledge about the situation. Similarly deciding what the prepositional
phrases attach to in sentences like the following clearly depends on your knowledge of what I am likely
to be saying, what kinds of nouns name common currencies, etc.
I bought the lock with the keys I bought the lock with my last dollar
I drove down the street in my car I drove down the street with the new asphalt
The decisions we make here are presumably non-linguistic too.
Suppose that we have augmented our lexical items for names with an indication that they denote a member
of the set e of individuals, and that we have augmented the intransitive verb e → t to indicate that it can be
regarded as a property, a function that tells you of each thing x ∈ e whether it’s true that x has the property.
Then the particular circumstances of utterance are typically relied upon to further clarify the matter, so that
we know which individual is intended by George, andwhichsense of charge is intended by charge. Wecould
depict the general situation like this, indicating the inferences made by the listener with dashed lines:
things that
actually charge in
the sense of run toward
things that you think
charge in the sense
of run toward
things actually named George
things you call George
derivation (lexical sequence): []:=T C −s::v=> +k T::habitually []::=>V =D v charge::V::e−>t George::D −k::e
abbreviated form: C(−s(v(charge,George)))
things that
actually charge in
the sense of make pay
x
things that you think
charge in the sense
of make pay
inferred, in context
For example, the listener could make a mistake about which sense of charge is intended, and the listener could
also be under some misconceptions about which things, exactly, really do charge in either sense. Either of
these things could make the listeners judgement about the truth of the sentence incorrect. For our purposes,
the important question is: What is the nature of the inferential processes here?
It has been generally recognized since the early studies of language in the tradition of analytic philosophy,
and since the earliest developments in modern formal semantics, that the problem of determining the
intended reading of a sentence, like the problem of determining the intended reference of a name or determiner
phrase is (i) non-linguistic, potentially involving virtually any aspect of the listener’s knowledge, and (ii)
249