Abstract not found

In this paper I will discuss the properties of a tactical generation approach that has become popular recently: head-driven bottom-up generation. It is assumed that bidirectional grammars written in some unificationor logic-based formalism define relations between strings and some representation, usually called logical form. The task for a generator is to generate for a given logical form the strings that are related to this logical form by the grammar. In the paper it will be shown that the `early' approaches to this conceivement of the generation problem such as [21], [31] and [7] are not entirely satisfactory for general purposes. Furthermore I will define a simple bottom-up generator, called BUG1 for reference, as prototypical for the head-driven bottom-up approach as defended by for example [30, 5, 23, 24]. I will argue that head-driven bottom-up generation is to be preferred because the order of processing is directed by the input logical form and the information available in le...

... that interpret large, reversible grammars. Only little attention has been paid so far to the many small and simple applications that require coverage of a small sublanguage at different degrees of sophistication. The system TG/2 described in this pa- per can be smoothly integrated with deep generation processes, it integrates canned text, templates, and context-free rules into a single formalism, it allows for both textual and tabular output, and it can be parameterized according to linguistic preferences. These features are based on suitably restricted production system techniques and on a generic backtracking regime.

this paper is that neither has been implemented." ([Vaughan and McDonald, 1986], page 95). Although Meteer [1990] gives a detail description of the relationship between text structure and revision it is unclear how the proposed model could contribute to the choice problem of paraphrases (see section 5.2). How- ever, from the approach described above and from the system described in [Meteer, 1990] we can draw the following conclusions. Only the generatoFs input is marked. If the generator encounters alternative realizations the revision component is asked to make the decision. However, to be able to do this it needs detailed knowledge about the grammar. Therefore grammatical knowledge has to be duplicated. The linguistic realization component used in [Meteer, 1990] is MUMBLE-86 [McDonald, 1986]. The text structural representation level must completely specify the infor- mation to be expressed by the utterance. The mapping has to ensure that all the necessary linguistic information is present. Mumblers procedural grammar is used only for generation purposes. Therefore it is without reach for the revision model to take into account relevant sources of ambiguities

Lexica! Grammars are a class of unification g,'ammars which share a fixed rule component, for which lhere exists a simple left-recursion elimination transformation. The parsing and generation programs ae seen as two dual non-left-recursive versions of the original grammar, and are implemented through a standard top-down Prolog interpreter. Formal criteria for termination are given as conditions on lexical enlrics: during parsing as well as during generution the processing of a lexical entry consumes some amount of a guide; the guide used for parsing is a list of words remaining to be analyzed, while the guide for genration is a list of the semantics of constituents waiting to be generated.

This paper attempts to clarify two distinct notions of "reversibility": (i) Uniforraity of implementation of parsing and generation, and (ii) reversibility as an inherent (or intrinsic) property of gram- mars. On the one hand, we explain why grammars specified as definite programs (or the various related "unification grammars") lead to uni- formity of implementation. On the other hand, we define different intrinsic reversibility properties for such grammars--the most important being finile reversibility, which says that both parsing and generation are finitely enumerable (see text)-- and give examples and counter-examples of grammars which possess or do not possess these intrinsic properties. We also show that, under a certain "moderation" condition on linguistic description, finite enumerability of parsing is equivalent to finite enumerability of generation.

Alfa-informatica & BCN, University of Groningen {vannoord, gosse}Olet. rug. nl parsers and generators for natural languages. The package is written in Sicstus Prolog and Tcl/Tk. The system provides a graphical user interface with a command interpreter, and a number of visualisation tools, including visualisation of fea- ture structures, syntax trees, type hierarchies, lexical hierarchies, feature structure trees, definite clause definitions, grammar rules, lexical entries, and graphs of statis- tical information of various kinds.

this paper we develop a functor-driven approach to natm, al language generation which pairs logical forms, expressed in first-order predicte logic, with syntactically well-formed English senteuces. Granmatical knowledge is expressed in the fi'amework of categorial unification-qrammars developed by Kart- tunen (1986), Wittenburg (1986), Uszkoreit (1986), and Zeevat st. al. (1987). The semantic component of the grammar makes crucial use of the principle of minimal type assignment whose imt)ortance has been Judependently notivatcd in recent work in natural language semantics (see Partes and Rooth 1.983). The principle of type-raising as necessary which follows fi'om miuimal type assignment has been imple- mented using Wittenburg's (1987,1989) idea of su percombinators. This use of superconbinators to achieve semantic cmnpatibility o[ types generalizes Wittenburg's strictly syntactic use of such combina- tors

We discuss the problems of translatin English to Sign Language in the ViSiCAST project. An overview of the language-processing component of an EnglishText to Sign-Languages translation system is described focusing upon the inherent problems of knowledge elicitation of sign language grammar and its implementation within a HPSG framework.

this paper, we describe the linguistic solutions to some of the problems encountered in writing a reversible French grammar. This grammar is primarily intended to be one of the components of a machine translation system built using ELU, 1 an enhanced PATR-II style unification grammar linguistic environment based on the UD system described in Johnson and Rosner (1989), but it is also part of our more general experimentation with fully reversible grammars. The requirement that it be reversible imposes a stringent criterion of linguistic adequacy on a gram- mar, sitice it is not allowed to overgenerate while it must at the same time provide a large coverage for analysis (Dymetman and Isabelle (1988)). Formally, grammw that are fully reversible must be completely declarative, since no retrence can be made in the grammar rules to the process (analyzer or synthesizer) which will use them. The unification formalism makes /tt possible to write such grammar statements, because due to the associativity and commutafivity of the unitication operation, the result of unifying feature stmctures is independent of the order in which they are unitled (Appelt (1989)). Writing reversible grammars, however, presents problems which do not arise in the traditional gram- mars used for either analysis or generation. In addi- tion, the progress accomplished recenfiy in building generators for unification grammars has already revealed some of the problems posed by tmification- based reversible grandmars. 2 As shown by Russell et at. (1990), even though the grammar rules do not refer to the generation process, the generation algorithm imposes particular constraints on the grammar formal- ism. 3 This paper concentrates particularly on the problems encountered in the generation of French, specifica...