Semantic Interpretation Using KL-ONE

case frames have significantly eased the development and expansion of semantic coverage within our application by helping us to focus on issues of generality and speciiicity. The new frames we add have many slots established by inheritance; consistency has been easier to maintain; and the structure of the resulting syntaxonomy has helped in debugging. 5. Semantically Neutral Terms Case frames are an attempt to characterize semantically coherent phrases, for instance, by selection restrictions. In computational linguistics, selection restrictions have been applied to the constituents that are possible fillers rather than to what the constituents denote. For example, the restriction on the direct object of a SEND-CLAUSE is MESSAGE-NP, rather than messages. Problems with using such approximations in parsing are discussed in [Ritchie 83]. For many natural language interfaces, a noun phrase's internal structure gives enough information to determine whether it satisfies a restriction, s However, there are forms whose semantic interpretation does not provide enough information to guarantee the satisfaction of a constraint and yet need to be allowed as fillers for slots. These include pronouns, some elliptical forms, such as "the last three", and otherneutral noun phrase forms, such as "the thing" and "the gift". This also includes some nonlexical gestural forms like the input from a display that shows where the user pointed (literally or via a mouse). We refer to all of these as sernantica//y neutra/terms. A semantic interpretation system should accept such forms without giving up restrictions on acceptable semantic categories. However, these forms cannot, in general, appear everywhere. In discussing computer mail, "1 sent him" should be considered nonsense. Bobrow and Webber [Bobrow&Webber 80b] propose a general strategy for testing the compatibility of a constituent as a slot filler based on non-incompatibility. The current system at USC/ISI takes a conservative view of this proposal, developing the idea for only neutral reference forms. All noun phrase types displaying neutral reference are defined as instances of the concept NeutraIReference.NP. Furthermore, disjointness" relations are marked between the various subclasses of neutral references and those classes of explicit descriptions which have nonintersecting sets of potential references. During interpretation, when such a NeutralReference-NP is proposed as a slot filler, and that concept is not disjoint from the value restriction on the slot, it is accepted. In addition, since the slot restriction and the filler each have meaning of their own, e.g., "he" describes a human male in the computer mail domain, the translation should show the contribution of both the neutral term and the constraint on the slot. When the neutral form is qualified as a constituent by the system, both the neutral form and the selection constraint are 9Clearly, misreference also intederes with this method [Goodman 8,3], as does personification, metonymy and synecdoche. We propose other methods for these last phenomena in [Weischedel 84, Weischedel 83]. remembered. When it is time to produce the translation, the translation rule for the slot applies to a concept which is the conjunction of the translations of the neutral reference form and the restriction. Part of the network that supports the translation of "he" in the example of section 1 is shown in Figure 6. Referring to Figures 2 and 3, the effect of a reference to a male where a reference to a computer-user was expected can be seen. ~ A N S L A T I O N : sex