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.

We introduce a new subclass of Allen's interval algebra we call "ORDHorn subclass," which is a strict superset of the "pointisable subclass." We prove that reasoning in the ORD-Horn subclass is a polynomial-time problem and show that the path-consistency method is sufficient for deciding satisfiability. Further, using an extensive machine-generated case analysis, we show that the ORD-Horn subclass is a maximal tractable subclass of the full algebra (assuming<F NaN> P6=NP). In fact, it is the unique greatest tractable subclass amongst the subclasses that contain all basic relations. This work has been supported by the German Ministry for Research and Technology (BMFT) under grant ITW 8901 8 as part of the WIP project and under grant ITW 9201 as part of the TACOS project. 1 1 Introduction Temporal information is often conveyed qualitatively by specifying the relative positions of time intervals such as ". . . point to the figure while explaining the performance of the system . . . "...

We review basic premises underlying the application of conceptual modelling to the development of information systems and point out a fundamental problem arising from the broad range of concepts that need to be modelled. We then argue that conventional conceptual models are weak for such broad domains of discourse because they come with built-in collections of primitive notions in terms of which conceptual modelling is to be done. Telos is then introduced as a conceptual modelling language designed for capturing knowledge about information systems and it is argued that, unlike its peers, it offers facilities not only for modelling an application but also the notions used to model an application. The presentation of features of the language is eclectic and generally non-technical. Details about Telos can be found in [Mylopoulos90] and [Koubarakis89].

1 Relational integrity checking technology can be transfered to deductive object bases by utilizing a simple logical framework for objects. The principles of object identity, aggregation and classification allow a more efficient constraint control by finer granularity of updates, composite updates and semantic constraint simplification. In many cases, meta-level constraints and deductive rules can be handled efficiently by a stepwise compilation approach. An extended integrity subsystem with these features has been implemented in the deductive object base ConceptBase. 1 This work was supported in part by the Commission of the European Community under ESPRIT Basic Research Action 3012 (CompuLog). A version of this paper will also appear in the Proc. Second Int. Conf. on Deductive and Object-Oriented Databases, Munich, Dec. 1991 1. Introduction Comprehensive and efficient integrity maintenance has been quoted as one of the major problems in next-generation databases. Systems l...

1 . Deductive object bases are extended database systems which amalgamate structural object-orientation with logical specification. Queries in such a system are regarded both as classes and as deduction rules. Besides a general architecture for query processing in deductive object bases, two specific query optimization techniques are presented: semantic query optimization with structural axioms of the object base, and view maintenance optimization. The approach has been formalized in the language Telos and implemented in the system ConceptBase. 1 This work has been supported in part by ESPRIT BRA 3012 Compulog. A version of this paper also appears in Freytag, Maier, Vossen (eds.): Query processing in objectoriented, complex-object, and nested relation databases, Morgan Kaufmann, 1992. 1 1. Introduction Traditionally, databases are systems for storing and accessing large amounts of shared persistent data in a secure way. Database research has always been concerned with pro...

This paper presents the architecture and basic features of the Ithaca Application Development Environment based on a Software Information System for enhancing reusability of both software components and artifacts about development of these components. Object-oriented techniques are used in the Environment at all levels of the development of an application: requirement specification, scripting, implementation through class refinement and tailoring. In the Environment, it is tracked how the various products of the development phases were produced by providing tools for the Application Engineer who is responsible for abstracting application skeletons and development information and storing these as Application Frames into a Software Information Base. In particular, the paper describes the Requirement Collection And Specification Tool (RECAST) and the Visual Scripting Tool (Vista) of the Ithaca Development Environment. *.In ACM SIGOIS Bulletin., Vol. 13, No. 2, Aug. 1992, pp. 38-47...

Abstract. This paper defines and analyses a computational model of similarity which detects analogies between objects based on conceptual descriptions of them, constructed from classification, generalization relations and attributes. Analogies are detected(elaborated) by functions which measure conceptual distances between objects with respect to these semantic modelling abstractions. The model is domain independent and operational upon objects described in non uniform ways. It doesn’t require any special forms of knowledge for identifying analogies and distinguishes the importance of distinct object elements. Also, it has a polynomial complexity. Due to these characteristics, it may be used in complex tasks involving intra or inter-domain analogical reasoning. So far the similarity model has been applied in the domain of software engineering. First, to support the specification of software requirements by analogical reuse and second, to enable the integration of requirements specifications, generated by the multiple agents involved in information system development. Details of these applications can be found in sited references. Also, we have conducted an empirical evaluation of: (i) the consistency of the estimates generated by the model against human intuition about similarity and (ii) its recall performance in tasks of analogi-cal retrieval, the results of which are presented in this paper. 1.

We present a logical framework for modeling and reasoning about requirements evolution in the construction of information systems. We illustrate how a sufficiently rich meta-level logic can formally and accurately capture intuitive ways of handling incompleteness and inconsistency in requirements and how operators that map between theories of this meta-level logic can provide a formal basis for requirements evolution. Specifically, our framework views a requirements model as a theory of some nonmonotonic logic, while requirements evolution involves mapping one such theory to another. We argue that the AGM theory of belief change [1] should provide the formal basis for the theory change component. We demonstrate our ideas by using the THEORIST system for nonmonotonic reasoning. As a demonstration of the utility of our framework, we analyze operators in the Telos system for requirements modeling to identify some obvious shortcomings. We then show how such problems can be addressed by def...

The CoAUTHOR system provides a real-time-oriented environment for multiple authors who wish to collaborate on the production of hypermedia documents. In this report, we describe a model of hypermedia document authoring, consider the group aspects of co-authoring, and the technical communication and coordination tools we areusing as a baSis for the implementation of a CoAUTHOR prototype. The interactions among the members of the authoring team concerning idea processing, document design and generation as well as group-specific activities such as critiquing issues, negotiating divergent-opinions, and treating inconsistent or incoin~ plete specifications are shown to be fairly knowledge-intensive and thus require maintenance facilities provided by a sophisticated knowledge base management system underlying the hypermedia surface. 1

The notion of context appears in several disciplines, including computer science, under various forms. In this paper, we are concerned with a notion of context in the area of conceptual modeling. First, we present a simple definition whereby a context is seen as a set of objects, within which each object has a set of names and possibly a reference: the reference of the object is another context which "hides" detailed information about the object. Then, we enhance our simple notion of context by structuring its contents through the traditional abstraction mechanisms, i.e. classification, generalization, and attribution. We show that, depending on the application, our notion of context can be used either as an alternative way of modeling or as a complement of the traditional abstraction mechanisms. Finally, we study the interactions between contextualization and the traditional abstraction mechanisms as well as the constraints that govern such interactions.