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<Paper uid="J90-3004">
  <Title>DISJUNCTION WITHOUT TEARS</Title>
  <Section position="5" start_page="0" end_page="0" type="concl">
    <SectionTitle>
4 LIMITATIONS
</SectionTitle>
    <Paragraph position="0"> The example discussed above shows how we can replace disjunctive descriptions by conjunctive ones in two specific cases, namely in the description of the FORMs of lexical items and VP complements. We further suggested that this technique might be extendable to other uses of disjunctive specifications, such as the agreement properties of the NP the sheep or the case marking of the pronoun it. We have not, however, banished disjunction from the grammar of Computational Linguistics Volume 16, Number 3, September 1990 173 Allan Ramsay Disjunction without Tears English. We could hardly expect to, given that in some versions of unification grammar, e.g. FUG, the entire grammar is specified by a single disjunctive descriptor, which is required to unify with the description of any legal sentence. Just what are the limits of our technique? The following two restrictions seem crucial. (i) The elements of the disjunction must pick out points in some finite partition of the space of possibilities, preferably a small finite partition. (ii) The disjunction must not contain any placeholders (reentrance conditions). Consider for instance the word changes. For the sake of argument we will assume that this item has exactly two interpretations, as a plural noun and as a third person singular verb. We could represent the fact that it can be seen either as a noun or as a verb as follows:  This indicates that we can specify the major category of changes in terms of what it is not, though it does seem that this may be too cumbersome to be worthwhile. The real problem, however, is that the MINOR features will be expected to specify some value for AGR; but the value of AGR for this word depends on whether it is in fact a noun or a verb---it is plural as a noun, but singular as a verb. We simply cannot deal with this within our framework, and if we try to adapt the framework to accommodate it, then all the computational complexity will return.</Paragraph>
    <Paragraph position="1"> This is particularly significant when we consider information about subcategorization. It is widely, and very sensibly, argued that as much information as possible about constituent structure should be associated directly with lexical items. FUG, for instance, permits the description of a lexical item to contain a pattern that describes its complements, and UCG (Calder 1988) even goes so far as to specify that for many lexical items the major category is the subcategorization frame. It is clear that the range of possible subcategorization frames cannot effectively be expressed in terms of a small finite set; and even if it could, our technique would be inapplicable because of the complex dependencies between the choice of subcategorization frame and the values of other features. This is the critical restriction on our technique--that it cannot be used to eliminate the disjunctions that arise from different subcategorization frames and different phrase structure rules. Our aim is to replace unnecessary disjunctions, not to eliminate them from syntactic description entirely.</Paragraph>
    <Paragraph position="2"> We end by returning to our earlier remark that &amp;quot;the argument is equally applicable to any of the other standard formalisms (except perhaps GPSG).&amp;quot; Our analysis of our main example depended on the fact that we have general knowledge about the range of possible values for the feature FORM, which we used to modify local descriptions of this feature. In GPSG, however, local information about feature structures is not complete, since there is a full default logic specifying possible restrictions on what values are po,;sible or mandatory in various circumstances. It seems; likely that the interactions between this logic and our use of general knowledge about features will interact in ways that are at best hard to predict, and may even make our approach completely infeasible.</Paragraph>
  </Section>
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