Processing underspecified semantic representations in the constraint language for lambda structures

The constraint language for lambda structures (CLLS) is an expressive language of tree descriptions which combines dominance constraints with powerful parallelism and binding constraints. CLLS was introduced as a uniform framework for defining underspecified semantics representations of natural language sentences, covering scope, ellipsis, and anaphora. This article presents saturation-based algorithms for processing the complete language of CLLS. It also gives an overview of previous results on questions of processing and complexity.Liegt nicht vor

Underspecified beta reduction

For ambiguous sentences, traditional semantics construction produces large numbers of higher-order formulas,which must then be beta-reduced individually. Underspecified versions can produce compact descriptions of all readings, but it is not known how to perform beta reduction on these descriptions. We show how to do this using beta reduction constraints in the constraint language for lambda-structures (CLLS)

Processing underspecified semantic representations in the constraint language for lambda structures

The constraint language for lambda structures (CLLS) is an expressive language of tree descriptions which combines dominance constraints with powerful parallelism and binding constraints. CLLS was introduced as a uniform framework for defining underspecified semantics representations of natural language sentences, covering scope, ellipsis, and anaphora. This article presents saturation-based algorithms for processing the complete language of CLLS. It also gives an overview of previous results on questions of processing and complexity.Liegt nicht vor

Beta reduction constraints

The constraint language for lambda structures (CLLS) can model lambda terms that are known only partially. In this paper, we introduce beta reduction constraints to describe beta reduction steps between partially known lambda terms. We show that beta reduction constraints can be expressed in an extension of CLLS by group parallelism. We then extend a known semi-decision procedure for CLLS to also deal with group parallelism and thus with beta-reduction constraints

NP coordination in underspecified scope representations

Accurately capturing the quantifier scope behaviour of coordinated NPs can be problematic for underspecification systems that define constraints over semantic constructors. We present an extension to a hole-semantics like language that allows a natural representation of coordinated NPs, and a translation from partial scope requirements into constraints on the constructors. We conclude that the efficient decision procedures developed for constraints on semantic constructors enable the possible meanings of sentences containing coordinated NPs to be fully underspecified

Parallelism and tree regular constraints

Parallelism constraints are logical descriptions of trees. Parallelism constraints subsume dominance constraints and are equal in expressive power to context unification. Parallelism constraints belong to the constraint language for lambda structures (CLLS) which serves for modeling natural language semantics. In this paper, we investigate the extension of parallelism constraints by tree regular constraints. This canonical extension is subsumed by the monadic second-order logic over parallelism constraints. We analyze the precise expressiveness of this extension on basis of a new relationship between tree automata and logic. Our result is relevant for classifying different extensions of parallelism constraints, as in CLLS. Finally, we prove that parallelism constraints and context unification remain equivalent when extended with tree regular constraints

A new algorithm for normal dominance constraints

Dominance constraints are logical descriptions of trees. Efficient algorithms for the subclass of normal dominance constraints were recently proposed. We present a new and simpler graph algorithm solving these constraints more efficiently, in quadratic time per solved form. It also applies to weakly normal dominance constraints as needed for an application to computational linguistics. Subquadratic running time can be achieved employing decremental graph biconnectivity algorithms

A parser system for extensible dependency grammar

This paper introduces a parser system for the meta grammar formalism of Extensible Dependency Grammar (XDG). XDG is a generalisation of Topological Dependency Grammar (TDG) (Duchier-Debusmann01). The XDG parser system comprises a constraint-based parser for all possible instances of XDG, a statically typed grammar input language, and a flexible backend for handling parser output. A powerful graphical user interface provides for easy accessibility of all the functionality of the system. In the future, we will use the XDG parser system to accomodate new dependency grammar formalisms such as Semantic Topological Dependency Grammar (STDG), and to experiment with other interesting XDG instances

Constraint programming in computational linguistics

Constraint programming is a programming paradigm that was originally invented in computer science to deal with hard combinatorial problems. Recently, constraint programming has evolved into a technology which permits to solve hard industrial scheduling and optimization problems. We argue that existing constraint programming technology can be useful for applications in natural language processing. Some problems whose treatment with traditional methods requires great care to avoid combinatorial explosion of (potential) readings seem to be solvable in an efficient and elegant manner using constraint programming. We illustrate our claim by two recent examples, one from the area of underspecified semantics and one from parsing

An efficient graph algorithm for dominance constraints

Dominance constraints are logical descriptions of trees that are widely used in computational linguistics. Their general satisfiability problem is known to be NP-complete. Here we identify normal dominance constraints and present an efficient graph algorithm for testing their satisfiablity in deterministic polynomial time. Previously, no polynomial time algorithm was known