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

Stabler - Lx 185/209 2003
To deal with this problem, Charniak, Goldwater, and Johnson (1998) explore the prospects for using a
probabilistic chart parsing method that builds only the n best analyses (of each category for each span
of the input) for some n.
(4) Is it reasonable to think that a probabilistic language models can handle these disambiguation problems?
It is not clear that this question has any sense, since the term ‘probabilistic language model’ apparently
covers almost everything, including, as a limiting case, the simple, discrete models that we have been
studying previously.
However, it is important to recognize that the disambiguation problem is a hard one, and clearly involves
background factors that cannot be regarded as linguistic.
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 noun phrase is, at least, well beyond the analytical tools available now. See, e.g., Partee (1975, p80),
Kamp (1984, p39), Fodor (1983), Putnam (1986, p222), and many others. Putnam argues, for example,
that
…deciding – at least in hard cases – whether two terms have the same meaning or whether they
have the same reference or whether they could have the same reference may involve deciding
what is and what is not a good scientific explanation.
From this perspective, the extent to which simple statistical models account for human language use
is surprising! As we will see, while we say surprising and new things quite a lot, it is easy to discern
creatures of habit behind language use as well.
We briefly survey some of the most basic concepts of probability theory and information. Reading quickly
over at least §8.1.1-§8.1.3 is recommended, but the main thread of development can be followed by skipping
directly to §8.2.1 on page 159.
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