During the preparation of my Ph. D. I have mainly studied pure theoretical problems like formal languages, automata, high-level languages, linear shifting, stochastic structures and context-free languages.

    After my Ph. D., I have been working in the research lab of MBLE-Philips in Brussels. We have implemented RHIL and FQL, both relational database languages of different levels. In that period I also studied the relational algebra, the functional dependencies and the multivalued dependencies in a relational database.
    More specifically I introduced a generalization of the numerous dependencies that were studied in that period. I looked at their properties and their inference rules. We proved a complete set of rules. It is important here to find a syntax and a semantics for expressing this kind of inference rules.

    The general dependencies also deduce a complex decomposition of a relational database. As a result of this we could define a new normal form. The latter was verified in a number of applications.

    We defined a basic property for database languages, which was called later on the BP-completeness (Bancilhon-Paredaens completeness) and was related to genericity.

    Classical dependencies give rise to vertical decompositions. We studied horizontal decompositions that were induced by a new kind of constraint. In this way we could isolate the exceptions of functional dependencies.

    Join dependencies are well known. The acyclic join dependencies have been studied earlier. We studied the cyclic join dependencies and describe some cases where these dependencies are meaningful.

    Decision Support Systems are complex information systems where updates and interactions with the outside world play an important role. Their formal definition has been given and isomorphisms and equivalences were studied.
    A special language has been defined to specify DSSs. This language was implemented in the TU Eindhoven.

    Distributed Database Systems communicate by sending transactions between their sites. We studied a number of properties of such distributed systems.

    Systolic systems are multi-process systems where a central managing clock synchronizes all the processes. Different aspects were studied and an implementation above Ada was realized.

    Structured Query Language (SQL) is the standard relational query and data managing language for relational databases. It was developed by IBM. Many implementations of SQL have been studied and compared.
    We developed a nested relational algebra with aggregation and recursion. We studied subclasses of this algebra and characterized its expressive power. We also introduced a two-dimensional notation for schemata as well as for instances. This study was closely related to subjects as complex objects, the nested relational model, nesting and unnesting and the expressive power of adding recursion and powerset.

    The Grammatical Data Model is a generalization of the hierarchical data model. We used grammars and the theory of formal languages in order to represent the structure of data, schemata and instances.

    We also developed 'MicroPakket', a number of programs used in secondary schools. It contains MicroPascal, MicroTekst and MicrEuclide, all of them implemented on MS-DOS and AppleII, with a user interface in Dutch.

    GOOD, a graphical interface, was developed. The fundamental properties of a graphical interface of a database were described, and on this base a formal graphical interface was designed and a prototype was built. It was implemented in Unix. In GOOD the user can query, update and restructure the database. This research was in cooperation with the Technical University of Eindhoven.
    G-log is a graphical deductive logical language. In this language one can deductively make use of rules to describe a problem on a non-procedural way. It is comparable with Prolog, but the rules are special graphs that describe conditions on the answers. These rules can include negation in the condition as well as in the conclusion, and are as such very powerful. This research was in cooperation with the University of Milano.

    Formal and fundamental aspects of object oriented databases were studied in the context of persistency, inheritance, object identity and encapsulation.
    We were more particularly interested in the influence of object orientation and set manipulation on the expressive power of a database language.

    A subject that is independent of databases is the design and implementation of software for handicapped persons, which has done in cooperation with Modem.

    In the context of spatial databases we studied topological aspects associated to genericity and using the polynomial data model for representation. This was generalized in a co-authored book on constraint databases.

    In data mining we studied different kinds of patterns. Association rules and frequent sets are the most important. Their interaction and their inference rules are used in several algorithms

    During the nineties XML became important as an intermediate format for documents and information in general. This was the start of XML-databases.
    First we studied XPath as an elegant but simple XML language. Our contribution in this field was the measure of the expressive power on document level. More powerful is XQuery, a Turing complete XML query language. We designed a sublanguage, LightXQuery, with its formal syntax and semantics. We also added update and restructuring operators to the language.

    We formalized some aspects of workflows by using Petri Nets. In this way we want to integrate the process and the data description of a workflow. On the other hand this gives the bases and the formal properties to build and characterize a workflow.


    Courses given in the period from 1970:

    At the 'Université Libre de Bruxelles'
    At the 'Vrije Universiteit Brussel'
    At the 'Universitaire Instelling Antwerpen'-'Universiteit Antwerpen'
    At the 'Technische Universiteit Eindhoven'



    Referee of several international journals, mainly:
    Chairman of several international conferences and scientific organizations, mainly :
    Member of the Program Committee of several international scientific conferences, mainly :


    Important scientific cooperation with several colleagues, mainly :



    In the University of Antwerp :

    Abroad :


    [1]Gabriel M. Kuper, Leonid Libkin, and Jan Paredaens, editors. Constraint Databases. Springer, 2000.
    [2]Joachim Biskup, T. Demetrovic, Jan Paredaens, and Bernhard Thalheim, editors. Proc. of the First Symposium on Mathematical Fundamentals of Database Systems. Number 305 in Lecture Notes in Computer Science. Springer-Verlag, Dresden, GDR, 1996.
    [3]L. Tanenbaum and Jan Paredaens, editors. Advances in Database Systems, Implementation and Applications. Number 347 in Advances in Database Systems, Implementation and Applications. CISM Courses and Lectures. Springer-Verlag, 1994.
    [4]Paul De Bra, Henk Olivié, and Jan Paredaens. Leren programmeren met Pascal. C. Kluwer Bedrijfswetenschappen, Deventer, 1992.
    [5]Jan Paredaens, Paul De Bra, Marc Gyssens, and Dirk Van Gucht. The Structure of the Relational Database Model. Springer-Verlag, 1989.
    [6]Henk Olivié and Jan Paredaens. Leren Programmeren met Turbo Pascal en Pascal. H.E.Stenfert Kroese B.V., 1988.
    [7]Henk Olivié, Jan Paredaens, and P. Schavey. Aan het werk met MicroPascal. H.E. Stenfert Kroese B.V., 1987.
    [8]Jan Paredaens. Databases. Academic Press, 1987.
    [9]J. Lewi and Jan Paredaens. Data Structures of Pascal, Algol 68, PL/1 and Ada. Springer-Verlag, 1986.
    [10]Henk Olivié and Jan Paredaens. Leren Programmeren met Pascal. H.E.Stenfert Kroese B.V., 1982.


    Publications of Jan Paredaens