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Image A Constraint Logic Programming Tool

Prolog IV offers a powerful, high performance programming tool for all applications based on mathematical optimisation.


The development of Prolog IV, a new constraint logic programming (CLP) language, is an outstanding achievement. The product of decades of fundamental and applied research and systems development, Prolog IV brings with it significant improvements in power and performance compered to its predecessor Prolog III. The richness of the constraint language enables Prolog IV to be applied to a very wide range of problems including scheduling or industrial planning applications, financial forecasting, or complex modelling in physics and chemistry.

Business perspective

Potential users of Prolog IV span a broad range of industries, services and commerce. Firstly, manufacturing industries are increasingly looking for tools to help plan, schedule and manage their production processes. For example, CLP systems have been used for the development of industrial scheduling and optimal stock-cutting applications.

Likewise, in the service sector CLP has been used to solve similar optimisation problems such as the development of banking forecast applications. Secondly, Prolog IV may be used in more traditional Prolog applications, such as the filtering and comparing of files according to various criteria. Its advantage here is to combine the powerful knowledge representation framework inherited from Prolog, with a powerful numberial handling package.

Finally, CLP is often taught as part of an advanced computer science curriculum, and in France, PrologIA is the leading supplier of logic programming and CLP to universities for teach support. The strong theoretical background of Prolog IV will make it a useful educational tool, to be used throughout Europe.

Technical perspective

CLP languages have become increasingly popular because they require a high level of formalization of a problem, enabling it to be used by a wider audience and as a training tool to teach the resolution of difficult problems. CLP technology also provides a high level of tools, allowing users to concentrate on the formalization and programming of a problem, rather than low-level implementation details such as memory management. Of the CLP languages, Prolog IV has the advantage of being theoretically sound, and, as it is inherited from Prolog, very simple. It will prove particularly useful as a prototyping tool, as the constraint approach is a very natural way of defining a problem, and the efficient algorithms used in Prolog IV will improve the prototype's performance. Finally, a Prolog IV program is easy to install into a large software package as great care has been given to the interface between Prolog IV and other languages and systems.


Prolog IV has been used to optimize crew scheduling for the Air Littoral airline company, which owns 26 planes, operates 1000 flights per week between 44 European cities and employs around 100 crew members. Using a wide range of parameters and constraints, the program provides a set of optimal duties, a set of duty summaries and a first proposal for a crew roster. This program is characterized by its simplicity whilst meeting all performance levels of its competitors.

Three new esprit projects are also using Prolog IV in the development and demonstration of new products, further validating its industrial value. These include the a Long Term Research project DISCipl and two esprit Trial Applications projects, VOCAL and TACIT.

Contact Point

Fabienne Leleu
PrologIA Parc Technologique de Luminy
Case 919
F-13288 Marseille
Cedex 09

e-mail (email removed)


Research Area Software Technologies

Project : 5246 PRINCE

Keywords constraint logic programming, parallel; knowledge-based systems; Prolog IV;

Project Participants
Banque la Henin FR
Katholieke Universiteit Leuven BE
PrologIA FR
Robert Bosch GmbH DE
Universidad Politecnica de Madrid ES
University of Bristol UK

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