Lynette van Zijl

South African Sign Language Machine Translation System

The South African Sign Language Machine Translation System (SASL-MT System) takes as its input English text, and outputs an avatar signing the equivalent SASL. This paper describes our experiences to date with the implementation of a signing avatar, in the light of the specific requirements of Sign Language.

South African sign language machine translation project

We describe the South African Sign Language Machine Translation project, and point out the role that the project is playing in the larger context of South African Sign Language and accessibility for the South African Deaf community.

The South African sign language machine translation project: issues on non-manual sign generation

We report on the South African Sign Language Machine Translation project, and more specifically on our experience in extending a synchronous tree-adjoining grammar parser approach in order to generate non-manual signs and construct a suitable signing space. We show that post-processing of the target language tree, after transfer rules have been applied, results in a simple and efficient mechanism to generate information on non-manual signs for use in a signing avatar.

On binary ⊕-NFAs and succinct descriptions of regular languages

We prove a new lower bound for the number of distinct languages accepted by binary symmetric difference automata (⊕-NFAs), and compare that to Domaratzkis results (J. Automata Languages Combin. 7(4) (2002) 469) for (traditional) binary nondeterministic finite automata (NFAs). We also show that there are certain regular languages which are accepted by succinct ⊕-NFAs, but for which no succinct traditional NFA exists.

The MERLin Environment Applied to *-NFAs

There are known mechanisms to succinctly describe regular languages, such as nondeterministic finite automata, boolean automata, and statecharts. The MERLin project is an investigation into and comparison of different description mechanisms for the regular languages. In particular, we are concerned with descriptions which, for a specific application domain, often achieve succinctness. To this end we implemented a Modelling Environment for Regular Languages (MERLin). This paper describes the application of the MERLin system to analyze the behaviour of selective nondeterministic finite automata.

Minimal DFA for symmetric difference NFA

Recently, a characterization of the class of nondeterministic finite automata (NFAs) for which determinization results in a minimal deterministic finite automaton (DFA), was given in [2]. We present a similar result for the case of symmetric difference NFAs. Also, we show that determinization of any minimal symmetric difference NFA produces a minimal DFA.

Reducing nondeterministic finite automata with SAT solvers

We consider the problem of reducing the number of states of nondeterministic finite automata, and show how to encode the reduction as a Boolean satisfiability problem. This approach improves on previous work by reducing a more general class of automata. Experimental results show that it produces a minimal automaton in almost all cases and that the running time compares favourably to the Kameda-Weiner algorithm.

Implementation experience with collision avoidance in signing avatars

We describe our experience with collision in signing avatars -- that is, avatars which are required to execute Sign Language. We present a generalized high-level automata-based model for collision avoidance in signing avatars, and illustrate it with an application of a fingerspelling hand for the International Sign Alphabet.

Random Number Generation with +-NFAs

We prove that unary symmetric difference nondeterministic finite automata have the same state cycle as linear feedback shift registers. This leads to the application of these automata for random number generation.

Ambiguity of unary symmetric difference NFAs

Okhotin [9] showed an exponential trade-off in the conversion from nondeterministic unary finite automata to unambiguous nondeterministic unary finite automata. In this paper, we consider the trade-off in the case of unary symmetric difference finite automata to finitely ambiguous unary symmetric difference finite automata. Surprisingly, the trade-off is linear in the number of states of the finite automaton. In particular, for every n-state unary nondeterministic symmetric difference finite automaton, there is an equivalent finitely ambiguous n-state unary symmetric difference nondeterministic finite automaton. We also note other relevant ambiguity issues in the unary case, such as the ambiguity of k-deterministic finite automata.