This paper describes a language that is intended to support software engineers in the development of information systems throughout the software lifecycle. This language is not a programming language. Following the example of a number of other software engineering projects, our work is based on the premise that information system development is knowledge-intensive and that the primary responsibility of any language intended to support this task is to be able to formally represent the relevant knowledge.

This paper presents an introduction for the ESPRIT community of the recently started ESPRIT 11 project, PLUS (P5254). The goal of the project is the production of a robust natural language dialogue system integrating linguistic and non-linguistic knowledge in a principled way, based on the pragmatics theories of Grice and Searle, and using results in knowledge-base management systems and logic programming for the maintenance of dynamic contextual knowledge bases. We present the background assumptions, an overview of the system conceptual design, of the empirical research that has already been undertaken on real corpora and of re-usable system components. 1