The Formal Architecture of Lexical-Functional Grammar
The Formal Architecture of Lexical-Functional Grammar
The Formal Architecture of Lexical-Functional Grammar
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4 /Ronald M. Kaplan<br />
representations re ect the fact that there are di erent kinds <strong>of</strong> informational<br />
dependencies among the parts <strong>of</strong> a sentence, and that these are<br />
best expressed using di erent formal structures. <strong>The</strong> goal is to account<br />
for signi cant linguistic generalizations in a factored and modular way by<br />
means <strong>of</strong> related but appropriately dissimilar representations.<br />
Elementary structures. We start with the simplest mathematical notion<br />
<strong>of</strong> a structure as a set <strong>of</strong> elements with some de ned relations and<br />
properties. <strong>The</strong> strings that make up a sentence such as (1) are a trivial<br />
example: the elements <strong>of</strong> the set are the words and immediate precedence<br />
is the only native relation. <strong>The</strong> looser nonimmediate precedence relation<br />
is speci ed indirectly, as the transitive closure <strong>of</strong> immediate precedence.<br />
(1) Isaw the girl.<br />
<strong>The</strong> phrase structure tree representing surface constituency con gurations<br />
(2)isaslightly more complex example. <strong>The</strong> elements <strong>of</strong> this structure are<br />
nodes which are labeled by parts <strong>of</strong> speech and abstract phrasal categories<br />
and satisfy native relations <strong>of</strong> precedence (a partial order in this case) and<br />
immediate domination.<br />
(2) S<br />
NP VP<br />
N V NP<br />
I saw Det N<br />
the girl<br />
To put it in more explicit terms, a tree consists <strong>of</strong> a set <strong>of</strong> nodes N related<br />
by a labeling function that takes nodes into some other nite labeling<br />
set L, a mother function M and that takes nodes into nodes, and a partial<br />
ordering