Abstract not found

The task of the knowledge-based presentation system WIP is the generation of a variety of multimodal documents from an input consisting of a formal description of the communicative intent of a planned presentation. WIP generates illustrated texts that are customized for the intended audience and situation. We present the architecture of WIP and introduce as its major components the presentation planner, the layout manager, the text generator and the graphics generator. An extended notion of coherence for multimodal documents is introduced that can be used to constrain the presentation planning process. The paper focuses on the coordination of contents planning and layout that is necessary to produce a coherent illustrated text. In particular, we discuss layout revisions after contents planning and the influence of layout constraints on text generation. We show that in WIP the design of a multimodal document is viewed as a non-monotonic planning process that includes various revisions of preliminary results in order to achieve a coherent output with an optimal media mix. 1

The acceptance of natural language generation systems strongly depends on their capability to facilitate the exchange of information with human users. Current generation systems consider the influence of situational factors on the content and the form of the resulting utterances. However, the need to time their processing flexibly is usually neglected although temporal factors play a central part when directly addressing a human communication partner. A short response time of a system is crucial for its effective use. Furthermore, some applications --- e.g., the simultaneous description of ongoing events --- even necessitate the interleaving of input consumption and output production, i.e. the use of an incremental processing mode. We claim that incremental processing is a central design principle for developing flexible and efficient generators for speech output. We discuss the advantages of parallel processing for incremental generation and several aspects of control of the generator...

Multimodal interfaces combining, e.g., natural language and graphics take advantage of both the individual strength of each communication mode and the fact that several modes can be employed in parallel, e.g., in the text-picture combinations of illustrated documents. It is an important goal of this research not simply to merge the verbalization results of a natural language generator and the visualization results of a knowledgebased graphics generator, but to carefully coordinate graphics and text in such a way that they complement each other. We describe the architecture of the knowledge-based presentation system WIP which guarantees a design process with a large degree of freedom that can be used to tailor the presentation to suit the specific context. In WIP, decisions of the language generator may influence graphics generation and graphical constraints may sometimes force decisions in the language production process. In this paper, we focus on the influence of graphical constraints on text generation. In particular, we describe the generation of cross-modal references, the revision of text due to graphical constraints and the clarification of graphics through text.

Current research in natural language generation is situated in a computational linguistics tradition that was founded several decades ago. We critically analyse some of the architectural assumptions underlying existing systems and point out some problems in the domains of text planning and lexicalization. Guided by the identification of major generation challenges viewed from the angles of knowledge-based systems and cognitive psychology, we sketch some new directions for future research.

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

Exploiting an incremental and parallel processing scheme is useful to improve the performance of natural language generation systems. TAG--GEN is a TAG--based syntactic generator that realizes both principles. It is shown how the demands of incremental and parallel generation influence the definition, the design, and the processing of syntactic rules on the basis of Tree Adjoining Grammars. Keywords Natural Language Generation, Incremental Processing, Tree Adjoining Grammar 1 Introduction The growing importance of natural language for human--computer interfaces motivates researchers in the field of artificial intelligence to search for methods that improve the performance of those systems. We developed the flexible and efficient syntactic generator TAG-- GEN as part of the text--generation module of the multi--modal presentation system WIP 1 (cf. [Wahlster et al. 92], [Wahlster et al. 93]). The design of TAG--GEN has been influenced by a number of goals (see [Kilger & Finkler 93])...

This paper describes the construction of syntactic structures within an incremental multi-level and parallel generation system. Incremental and parallel generation imposes special requirements upon syntactic descr:.ption and processing. A head-driven grammar represented in a unification-based formalism is introduced which satisfies these demands. Furthermore the basic mechanisms for the parallel processing of syntactic segments are presented.

The majority of existing language generation systems have a pipeline architecture which offers efficient sequential execution of modules, but does not allow decisions about text content to be revised in later stages. However, as exemplified in this paper, in some cases choosing appropriate content can depend on text length and formatting, which in a pipeline architecture are determined after content planning is completed. Unlike pipelines, interleaved and revision-based architectures can deal with such dependencies but tend to be more expensive computationally. Since our system needs to generate acceptable hypertext explanations reliably and quickly, the pipeline architecture was modified instead to allow additional content to be requested in later stages of the generation process if necessary. 1

This paper shows how the use of reversible grammars may lead to efficient and flexible natural language parsing and generation systems. In particular a mechanism is described which ensures that only non-ambiguous utterances are produced. This mechanism uses the parsing component to monitor the generation component. The relevant communication between the two components is performed using derivation trees. For this reason the proposed mechanism only makes sense for systems in which a single grammar is used for both parsing and generation. Furthermore we define a variant of the monitoring strategy which can be used to paraphrase a given input sentence (for interactive disambiguation). In this case, the generation component is used to guide the parsing system. Again the proposed technique is possible only in the case of a single, reversible grammar.