John R. W. Glauert

Term graph rewriting

Graph rewriting (also called reduction) as defined in Wadsworth [1971] was introduced in order to be able to give a more efficient implementation of functional programming languages in the form of lambda calculus or term rewrite systems: identical subterms are shared using pointers.

The development of language processing support for the ViSiCAST project

ViSiCAST is a major new project funded by the European Union, aiming to provide improved access to services and facilities for deaf citizens through sign language presented by a virtual human, or avatar. We give here an outline of the project, and describe early work in the area of linguistics and language processing. This work covers two distinct but related areas: first, the development of an XML-compliant notation for deaf sign language gestures, which can be used to drive the signing avatar; and, second, the development of a framework supporting the translation of natural language text into this gesture-orientated notation.

Linguistic modelling and language-processing technologies for Avatar-based sign language presentation

Sign languages are the native languages for many pre-lingually deaf people and must be treated as genuine natural languages worthy of academic study in their own right. For such pre-lingually deaf, whose familiarity with their local spoken language is that of a second language learner, written text is much less useful than is commonly thought. This paper presents research into sign language generation from English text at the University of East Anglia that has involved sign language grammar development to support synthesis and visual realisation of sign language by a virtual human avatar. One strand of research in the ViSiCAST and eSIGN projects has concentrated on the generation in real time of sign language performance by a virtual human (avatar) given a phonetic-level description of the required sign sequence. A second strand has explored generation of such a phonetic description from English text. The utility of the conducted research is illustrated in the context of sign language synthesis by a preliminary consideration of plurality and placement within a grammar for British Sign Language (BSL). Finally, ways in which the animation generation subsystem has been used to develop signed content on public sector Web sites are also illustrated.

Providing signed content on the Internet by synthesized animation

Written information is often of limited accessibility to deaf people who use sign language. The eSign project was undertaken as a response to the need for technologies enabling efficient production and distribution over the Internet of sign language content. By using an avatar-independent scripting notation for signing gestures and a client-side web browser plug-in to translate this notation into motion data for an avatar, we achieve highly efficient delivery of signing, while avoiding the inflexibility of video or motion capture. Tests with members of the deaf community have indicated that the method can provide an acceptable quality of signing.

Dactl: An Experimental Graph Rewriting Language

Dactl is an experimental language programming language based on fine grain graph transformations. It was developed in the context of a large parallel reduction machine project. The design of the language is outlined, and examples given of its use both as a compiler target language and as a programming language. Dactl has a formal semantics and stable implementations on a number of platforms.

Towards an intermediate language based on graph rewriting

Lean is an experimental language for specifying computations in terms of graph rewriting. It is based on an alternative to Term Rewriting Systems (TRS) in which the terms are replaced by graphs. Such a Graph Rewriting System (GRS) consists of a set of graph rewrite rules which specify how a graph may be rewritten. Besides supporting functional programming, Lean also describes imperative constructs and allows the manipulation of cyclic graphs. Programs may exhibit non-determinism as well as parallelism. In particular, Lean can serve as an intermediate language between declarative languages and machine architectures, both sequential and parallel.

Sign Language Recognition, Generation, and Modelling: A Research Effort with Applications in Deaf Communication

Sign language and Web 2.0 applications are currently incompatible, because of the lack of anonymisation and easy editing of online sign language contributions. This paper describes Dicta-Sign, a project aimed at developing the technologies required for making sign language-based Web contributions possible, by providing an integrated framework for sign language recognition, animation, and language modelling. It targets four different European sign languages: Greek, British, German, and French. Expected outcomes are three showcase applications for a search-by-example sign language dictionary, a sign language-to-sign language translator, and a sign language-based Wiki.

Relative Normalization in Deterministic Residual Structures

This paper generalizes the Huet and Levy theory of normalization by neededness to an abstract setting. We define Stable Deterministic Residual Structures (SDRS) and Deterministic Family Structures (DFS) by axiomatizing some properties of the residual relation and the family relation on redexes in an Abstract Rewriting System. We present two proofs of the Relative Normalization Theorem, one for SDRSs for regular stable sets, and another for DFSs for all stable sets of desirable ‘normal forms’. We further prove the Relative Optimality Theorem for DFSs. We extend this result to deterministic Computation Structures which are deterministic Event Structures with an extra relation expressing self-essentiality.

Relative Normalization in Orthogonal Expression Reduction Systems

We study reductions in orthogonal (left-linear and non-ambiguous) Expression Reduction Systems, a formalism for Term Rewriting Systems with bound variables and substitutions. To generalise the normalization theory of Huet and Levy, we introduce the notion of neededness with respect to a set of reductions π or a set of terms \(\mathcal{S}\) so that each existing notion of neededness can be given by specifying π or \(\mathcal{S}\). We imposed natural conditions on \(\mathcal{S}\), called stability, that are sufficient and necessary for each term not in \(\mathcal{S}\)-normal form (i.e., not in \(\mathcal{S}\)) to have at least one \(\mathcal{S}\)-needed redex, and repeated contraction of \(\mathcal{S}\)-needed redexes in a term t to lead to an \(\mathcal{S}\)-normal form of t whenever there is one. Our relative neededness notion is based on tracing (open) components, which are occurrences of contexts not containing any bound variable, rather than tracing redexes or subterms.

Discrete Normalization and Standardization in Deterministic Residual Structures

We prove a version of the Standardization Theorem and the Discrete Normalization Theorem in stable Deterministic Residual Structures, Abstract Reduction Systems with axiomatized notions of residual, which model orthogonal rewrite systems. The latter theorem gives a strategy for construction of reductions Levy-equivalent (or permutation-equivalent) to a given, finite or infinite, regular (or semi-linear) reduction, based on the neededness concept of Huet and Levy. This and other results of this paper add to the understanding of Levy-equivalence of reductions, and consequently, Levys reduction space. We demonstrate how elements of this space can be used to give denotational semantics to known functional languages in an abstract manner.