Recent discussions of grammatical architectures have distinguished two competing approaches to the syntax-semantics interface: syntactocentrism, wherein syntactic structures are mapped or transduced to semantics (and phonology), vs. parallelism, wher

Standard possible worlds semantics has been known from the start to have a problem with granularity: for a wide range of natural-language (NL) entailment patterns, not enough meaning distinctions are available to make predictions consistent with robust intuitions. Though numerous solutions have been proposed, often of great ingenuity and technical sophistication, none of these has gained widespread acceptance. As a result, most semanticists have made a practical decision to work in a framework known to have dubious foundations and leave the foundational problems to mathematical logicians. Here, a new approach is proposed which may be simple enough and conservative enough to be practical for working empirical and computational semanticists. More specifically, I show how the use of a higher-order logic with definable subtypes leads to a novel and surprisingly straightforward solution of the granularity problem. I also call attention to a hitherto unnoticed problem in standard approaches to NL semantics having to do with non-principal ultrafilters and show why it does not arise under my proposal. The two main technical innovations that drive the proposal are (i) axiomatizing NL entailment as a preorder (as opposed to an order) on the set of (primitive) propositions, and (ii) defining worlds as certain sets of propositions (viz. ultrafilters). These innovations provide just the tools we need to develop a formally explicit theory of hyperintensions, 1 mathematical models of Fregean senses of a finer granularity than the familiar intensions (functions to extensions from worlds, where the worlds in turn are theoretical primitives) of mainstream Kripke/Montague-inspired NL semantics.

We propose a novel approach to extraposition in German within an alternative conception of syntax in which syntactic structure and linear order are mediated not via encodings of hierarchical relations but instead via order domains. At the heart of our proposal is a new kind of domain formation which affords analyses of extraposition constructions that are linguistically more adequate than those previously suggested in the literature.

We investigate the logical structure of concepts generated by conjunction and disjunction over a monotonic multiple inheritance network where concept nodes represent linguistic categories and links indicate basic inclusion (ISA) and disjointness (ISNOTA) relations. We model the distinction between primitive and defined concepts as well as between closed-and open-world reasoning. We apply our logical analysis to the sort inheritance and unification system of HPSG and also to classification in systemic choice systems.

In this paper we present a formalization of the centering approach to modeling attentional structure in discourse and use it as the basis for an algorithm to track discourse context and bind pronouns. As described in [GJW86], the process of centering attention on entities in the discourse gives rise to the intersentential transitional states of continuing, retaining and shifting. We propose an extension to these states which handles some additional cases of multiple ambiguous pronouns. The algorithm has been implemented in an HPSG natural language system which serves as the interface to a database query application.

In the new Head-driven Phrase Structure Grammar (HPSG) language processing system that is currently under development at Hewlett-Packard Laboratories, the Montagovian semantics of the earlier GPSG system (see [Gawron et al. 1982]) is replaced by a radically different approach with a number of distinct advantages. In place of the lambda calculus and standard first-order logic, our medium of conceptual representation is a new logical formalism called NFLT (Neo-Fregean Language of Thought); compositional semantics is effected, not by schematic lambda expressions, but by LISP procedures that operate on NFLT expressions to produce new expressions. NFLT has a number of features that make it well-suited for natural language translations, including predicates of variable arity in which explicitly marked situational roles supercede order-coded argument positions, sortally restricted quantification, a compositional (but nonextensional) semantics that handles causal contexts, and a principled conceptual raising mechanism that we expect to lead to a computationally tractable account of propositional attitudes. The use of semantically compositional LISP procedures in place of lambda-schemas allows us to produce fully reduced translations on the fly, with no need for post-processing. This approach should simplify the task of using semantic information (such as sortal incompatibilities) to eliminate bad parse paths.

The lexicon now plays a central role in our implementation of a Head-driven Phrase Structure Grammar (HPSG), given the massive relocation into the lexicon of linguistic information that was carried by the phrase structure rules in the old GPSG system. HPSG's grammar contains fewer than twenty (very general) rules; its predecessor required over 350 to achieve roughly the same coverage. This simplification of the grammar is made possible by an enrichment of the structure and content of lexical entries, using both inheritance mechanisms and lexical rules to represent the linguistic information in a general and efficient form. We will argue that our mechanisms for structure-sharing not only provide the ability to express important linguistic generalization about the lexicon, but also make possible an efficient, readily modifiable implementation that we find quite adequate for continuing development of a large natural language system.

The Head-driven Phrase Structure Grammar project (HPSG) is an English language database query system under development at Hewlett-Packard Laboratories. Unlike other product-oriented efforts in the natural language understanding field, the HPSG system was designed and implemented by linguists on the basis of recent theoretical developments. But, unlike other implementations of linguistic theories, this system is not a toy, as it deals with a variety of practical problems not covered in the theoretical literature. We believe that this makes the HPSG system unique in its combination of linguistic theory and practical application.The HPSG system differs from its predecessor GPSG, reported on at the 1982 ACL meeting (Gawron et al. ([1982]), in four significant respects: syntax, lexical representation, parsing, and semantics. The paper focuses on parsing issues, but also gives a synopsis of the underlying syntactic formalism.