[All BiBTeX entries for this year]

H.A. (Erik) Proper, and T.A. Halpin. * Conceptual Schema Optimisation - Database Optimisation before sliding down the Waterfall. *Technical report, July, Department of Computer Science, University of Queensland, Brisbane, Queensland, Australia, 1995.

In this article we discuss an approach to database optimisation in which a conceptual schema is optimised by applying a sequence of transformations. By performing these optimisations on the conceptual schema, a large part of the database optimisation can be done before actually sliding down the software development waterfall.

When optimising schemas, one would like to preserve some level of equivalence between the schemas before and after a transformation. We distinguish between two classes of equivalence, one based on the mathematical semantics of the conceptual schemas, and one on conceptual preference by humans.

As a medium for the schema transformations we use the universe of all (correct) conceptual schemas. A schema transformation process can then be seen as a journey (a schema- time worm) within this universe. The underlying theory is conveyed intuitively with sample transformations, and formalised within the framework of Object-Role Modelling. A metalanguage is introduced for the specification of transformations, and more importantly their semantics. While the discussion focusses on the data perspective, the approach has a high level of generality and is extensible to process and behaviour perspectives.

Denis Verhoef, and Th.P. van der Weide. * Gerichte ondersteuning voor systeemontwikkeling met bouwstenen. *Technical report: CSI-N9501, Maart, Radboud University Nijmegen, 1995.

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G. Barthe. * Toward a mathematical vernacular. *Technical report: CSI-N9502, July, Radboud University Nijmegen, 1995.

Although computer mathematics provide useful tools in some restricted areas of mathematics, it remains difficult to fully formalise complex mathematical theories with any of the existing systems. On the one hand, proof-development systems have the ability to capture elegantly informal logical reasoning but lack of computational power. On the other hand, computer algebra systems use a large collection of algorithms which confer it computational power but has no reasoning abilities. A new approach to design a system which could serve as a mathematical assistant is proposed, which distinguishes between the specification of such a system and its implementation. We address the issue of the specification of the system, which is a formal language called the vernacular and apply some of the ideas of the vernacular to enhance existing proof-development systems.

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J.W.G.M. Hubbers, and N.E. van Oosterom. * Modellering van interactie tussen Wegverkeerssystemen. *Technical report: CSI-N9505, Computing Science Institute, University of Nijmegen, Nijmegen, The Netherlands, 1995, In Dutch.

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Drs. J.W, and Drs. N.E. * Modellering van Interactie tussen Wegverkeerssystemen:. *Technical report: CSI-N9506, September, Radboud University Nijmegen, 1995.

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Drs. J.W, and Drs. N.E. * Modellering van Interactie tussen Wegverkeerssystemen:. *Technical report: CSI-N9507, September, Radboud University Nijmegen, 1995.

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C.H.A. Koster. * The Making of Algol 68. *Technical report: CSI-N9508, October, Radboud University Nijmegen, 1995.

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A. Valente, and P. van Bommel. * From KISS to Implementation: A Study of Problems, Solutions, and Open Issues. *Technical report: CSI-N9509, Computing Science Institute, University of Nijmegen, Nijmegen, The Netherlands, 1995.

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P.J.M. Frederiks, and Th.P. van der Weide. * Fundamentals of Object Orientation in KISS. *Technical report: CSI-N9601, May, Computing Science Institute, University of Nijmegen, 1995.

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E.S.C. van de Ven, P. van Bommel, P.J.M. Frederiks, and Th.P. van der Weide. * Natural Language Properties and Information Systems. *Technical report: CSI-N9608, Computing Science Institute, University of Nijmegen, 1995.

In this paper the concept of natural language is discussed from three perspectives: which properties does natural language have from a psychologic point of view, how are natural language sentences built, and what is their meaning? The paper serves as a basis for applying natural language in information systems engineering.

A.A.F. van der Maas, A.H.M. ter Hofstede, and P.F. de Vries Robbï¿½. * Towards formal patient case analysis:. *Technical report: CSI-R9503, March, Radboud University Nijmegen, 1995.

Patient case analysis is an elementary and crucial process clinicians are daily confronted with. The extent and complexity of this process makes the usefulness of computer assistence obvious. Any kind of computer support of patient case analysis requires unambiguous detailed representation of patient cases. The focus in this paper is on generic modelling of temporal knowledge as present in patient cases. % and the realization of computer support.The lack of a generic technique to model temporal patient specific knowledge is reflected by the fact that gathering of patient specific temporal information for the purpose of computer manipulation always is controlled and guided by a specific disease or treatment model.This paper introduces a %generic modelling technique generic patient case description language (PCDL) based on general medical temporal concepts to formalise temporal knowledge, as present in patient cases.

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F.A.M. van den Beuken. * Polymorphism in Funmath. *Technical report: CSI-R9504, May, Radboud University Nijmegen, 1995.

Polymorphic typing is an important feature for system description languages. Polymorphism makes it possible to abstract from the domain of application when specifying a system. As a result, the same polymorphic specification can be used in different application areas in a uniform manner. This paper shows how different forms of polymorphism are accomplished in the declarative functional language Funmath.To obtain a formal notion of polymorphism, a function merge operator is defined and some important properties are given. This function merge operator is then used to define the functional type merge operator, which will be used to construct polymorphic types in Funmath. The type merge operator has a very wide application domain. However, in practice it's almost exclusively used to merge simple function types. Therefore, a theorem is given which shows how the type merge operator specializes to simple function types, so that it can be used in practice more easily.Using the type merge operator and the theorem it is shown how Curry-style polymorphism can be expressed in Funmath. By regarding overloading as a finite kind of polymorphism, the same approach can also be used to give types to overloaded operators.Finally it is shown how Funmath record types can be combined with polymorphism to deal with extensible records. This is done using a subtype relation on product types, which later is extended to arbitrary function types. The resulting subtyping system with merge types is compared to an existing typing system with intersection types.

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P.G.H. Toonen, and P. van Bommel. * Markov Chain Fundamentals for Data Schema Transformations. *Technical report: CSI-R9505, Computing Science Institute, University of Nijmegen, Nijmegen, The Netherlands, 1995.

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F.J.M. Panken. * The Interdeparture Time Distribution For Each Class in The ï¿½ï¿½MS([X];i)ï¿½/Gi/1 Queue with Set-Up Times and Repeated Server Vacations . *Technical report: CSI-R9506, May, Radboud University Nijmegen, 1995.

We study the interdeparture time distribution for one class of customers arriving at a single server queue where customers of several classes are served and where the server takes a vacation whenever the system appears to be empty. Furthermore, we allow the first customer in the busy period to have an exceptional service time (set-up time), dependent of the class to which this customer belongs. Batches of customers of each class arrive according to independent Poisson processes and compete with each other on a FIFO basis. All customers who belong to a certain class are served according to a generally distributed service time. Service times, batch sizes and the arrival process are all assumed to be mutually independent. Successive vacation times of the server form independent and identically distributed sequences with a general distribution. For this queueing model we obtain the Laplace transform of the interdeparture time distribution for each class of customers whose batch size is geometrically distributed. We do not make explicit assumptions about the batch size distribution of the other classes of customers. We discuss applications of our results for a protocol which controls a shared access medium for an ATM network.

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G. Barthe. * A simple abstract semantics for equational theories. *Technical report: CSI-R9507, July, Radboud University Nijmegen, 1995.

We introduce an order-sorted logic with term-declarations QTDL and give two abstract constructions which characterise uniquely the category of algebras of a specification. The first construction uses order-sorted composita, a set-theoretical notion generalising Nerode's composita. Composita can be used to capture in a precise mathematical way the intuition that the category of algebras of most equational theories is completely characterised by one term algebra. The second construction uses order-sorted monads. In the second part of the paper, we exploit the correspondence between composita and equational theories to solve an open problem raised in [Williams, 1991], namely the embedding of an order-sorted compositum into an unsorted one.

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G. Barthe. * Formalising mathematics in UTT: . *Technical report: CSI-R9508, July, Radboud University Nijmegen, 1995.

We give a detailed account of the use of type theory as a foundational language to formalise mathematics. We develop in the type system UTT a coherent approach to naive set theory and elementary mathematical notions. In the second part of the paper, we present a fully-checked example based on our representation of naive set theory.

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G. Barthe. * Strong normalisation of quotient and subset types in higher order logic. *Technical report: CSI-R9509, July, Radboud University Nijmegen, 1995.

In {[Jacobs], 7} a new syntax for quotient types in a predicatelogic over a simple type theory is introduced. We prove that the extension preserves strong normalisation. Finally, we show how the proof can be adapted to prove strong normalisation for subset types, as introduced in {[Jacobs], 6}.

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A.H.M. ter Hofstede, E. Lippe, and Th.P. van der Weide. * A Categorical Framework for Conceptual Data Modeling: Definition, Application, and Implementation. *Technical report: CSI-R9512, November, Computing Science Institute, University of Nijmegen, Nijmegen, The Netherlands, 1995.

For successful information systems development, conceptual data modeling is essential. Nowadays a plethora of techniques for conceptual data modeling exist. Many of these techniques lack a formal foundation and a lot of theory, e.g. concerning updates or schema transformations, is highly data model specific. As such there is a need for a unifying formal framework providing a sufficiently high level of abstraction. In this paper the use of category theory for this purpose is addressed. Wellknown conceptual data modeling concepts, such as relationship types, generalization, specialization, and collection types are discussed from a categorical point of view. An important advantage of this framework is its ``configurable semantics''. Features such as null values, uncertainty, and temporal behavior can be added by selecting appropriate instance categories. The addition of these features usually requires a complete redesign of the formalization in traditional setbased approaches to semantics. Applications of the framework in the context of schema transformations and improved automated modeling support are discussed.

A.H.M. ter Hofstede, F.J.M. Bosman, and Th.P. van der Weide. * Towards a Data Modeling Shell. *Technical report: CSI-R9513, November, Radboud University Nijmegen, 1995.

Much research has been performed into improved automatedmodeling support. Ideally, a modeling support environmentis highly flexible and allows analysts to define theirown concepts and ways of working.While in general this seems an unattainable goal,for specific types of modeling techniques this mightbe achieved. In this paper, a data modeling shell is discussedwhich is based on a framework for conceptual data modelingtechniques embedded in category theory. An important propertyof the framework is its ``configurable semantics'',which means that features such as null values, uncertainty, and temporalbehavior can be added by selecting appropriate instance categories.Hence, the data modeling shell not only allows syntactic conventions,including representational aspects, to be customized for a conceptualdata modeling technique,it also allows a choice of required semantic features.

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P.J.M. Frederiks, C.H.A. Koster, and Th.P. van der Weide. * Object-Oriented Analysis using Informal Language. *Technical report: CSI-R9516, December, Computing Science Institute, University of Nijmegen, Nijmegen, The Netherlands, 1995.

In this paper we study one aspect of the analysis of information systems, viz., how to obtain a (formal) model using informal formulations. We give a general framework for this modeling process, and also discuss the cognitive identity of domain experts. The starting point of the modeling process is a set of formulations (intended as an informal specification). Initially, these formulations need not form a complete and consistent specification. In an iterative process, alternating deduction and induction, an informal specification and corresponding formal model are to be derived. Rather than aiming at one (large) model, certain partial models are derived that collectively describe the application domain in a complete and consistent fashion. This process involves both domain expert and system analyst, communicating primarily in natural language.

This communication is supported by a system analyzing informal formulations to obtain fragments of the (formal) model, and paraphrasing fragments of this model to obtain feedback. This feedback mechanism is intended to support the validation of the model, regarding both structural aspects and constraints on populations.