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

Stabler - Lx 185/209 2003
(4) More formally, the structure building rules can be formulated like this:
• • structure building (partial) function: merge : (exp × exp) → exp
Letting t[f] be the result of prefixing feature f to the sequence of features at the head of t, for all trees t1,t2
all c ∈ Cat,
⎧
<
⎪⎨ t1 t2 if t1 ∈ Lex
mer ge(t1[=c], t2[c]) =
>
⎪⎩
• structure building (partial) function: move : exp → exp
t2 t1 otherwise
Letting t > be the maximal projection of t,
for any tree t1[+f] which contains exactly one node with first feature -f
move(t1[+f]) =
t > 2
>
t1{t2[-f] > /ɛ}
(5) In sum:
Each lexical item is a (finite) sequence of features.
Each structure building operation “checks” and cancels a pair of features.
Features in a sequence are canceled from left to right.
Merge applies to a simple head and the first constituent it selects by attaching the selected constituent
on the right, in complement position. If a head selects any other constituents, these are attached to the
left in specifier positions.
All movement is overt, phrasal, leftward. A maximal subtree moves to attach on the left as a specifier
of the licensing phrase.
One restriction on movement here comes from the requirement that movement cannot apply when two
outstanding -f requirements would compete for the same position. This is a strong version of the
“shortest move” condition (Chomsky, 1995).
We may want to add additional restrictions on movement, such as the idea proposed by Koopman and
Szabolcsi (2000a): that the moved tree must be a comp + or the specifier of a comp + .Wewillconsider
these issues later.
These operations are asymmetric with respect to linear order! So they fit best with projects in “asymmetric
syntax:” Kayne (1994), Kayne (1999), Koopman and Szabolcsi (2000a), Sportiche (1999), Mahajan
(2000), and many others. It is not difficult to extend these grammars to allow head movement, adjunction
and certain other things, but we will stick to these simple grammars for the moment.
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