Introduction to Computational Linguistics

16. Finite State Morphology 60
(‘for a drum’) dobbal (‘with a drum’); szeg (‘nail’) szegnek (‘for a nail’) and
szeggel (‘with a nail’).) On the other hand, there are a handful of words that end
in z (ez ‘this’, az ‘that’) where the final z assimilates to the following consonant
(ennek ‘to this’), except in the comitative where we have ezzel ‘with this’. To
write a finite state transducer, we need to record in the state two things: whether
or not the root contained a back vowel, and what consonant the root ended in.
Plural in German is a jungle. First, there are many ways in which the plural
can be formed: suffix s, suffix en, suffix er, Umlaut, which is the change (graphically)
from a to ä, from o to ö and from u to ü of the last vowel; and combinations
thereof. Second, there is no way to predict phonologically which word will take
which plural. Hence, we have to be content with a word list. This means, translated
into finite state machine, that we end up with a machine of several hundreds
of states.
Another area where a transducer is useful is in writing conventions. In English,
final y changes to i when a vowel is added: happy : happier, fly : flies. In
Hungarian, the palatal sound [dj] is written gy. When this sound is doubled it
becomes ggy and not, as one would expect, gygy. The word hegy should be
the above rule become hegygyel, but the orthography dictates heggyel. (Actually,
the spelling gets undone in hyphenation: you write hegy-gyel.)
Thus, the following procedure suggests itself: we define a machine that regularizes
the orthography by reversing the conventions as just shown. This machine
translates heggyel into hegygyel. Actually, it is not necessary that gy is treated
as a digraph. We can define a new alphabet in which gy is written by a single
symbol. Next, we take this as input to a second machine which produces the deep
morphological representations.
We close with an example from Egyptian Arabic. Like in many semitic languages,
roots only consist of consonants. Typically, they have three consonants,
for example ktb ‘to write’ and drs ‘to study’. To words are made by adding some
material in front (prefixation), some material after (suffixation) and some material
in between (infixation). Moreover, all these typically happen at the same time.