Based on a few constraint programming languages which support the storage of basic constraints and the waking and resuspension of constraint agents, the technology has achieved a number of remarkable successes on benchmarks and, more importantly, real industrial applications. A recent survey of practical applications of constraint programming (Wallace, 1996) estimated the annual revenue from constraint technology at around 100 million dollars per annum.
One early application, developed in 1990, was to container port planning in Hong Kong. The application was built by ICL, using finite domain constraints. Another early user was Siemens, who have applied Boolean constraints to problems of circuit design and integration. Both Siemens and Xerox are now applying constraints to real time control problems.
Constraints are used for graphical interface design and implementation at Object Technology International. Constraint-based scheduling has made a big impact in the USA, with applications in heavy industry, NASA and the Army. The application developers are typically small companies such as Recom, Red Pepper and the Kestrel Institute.
One company, ILOG, has sold constraint technology both in the USA and Europe. ILOG also have applications in south east Asia. Its French rival, Cosytec, is perhaps the only company to make all its business from constraint technology and applications. (Cras, 1993) gives a survey of industrial constraint solving tools.
Areas where constraint programming has proven very successful include scheduling, rostering and transportation. Constraints are used for production scheduling in the chemical industry, oil refinery scheduling, factory scheduling in the aviation industry, mine planning and scheduling, steel plant scheduling, log cutting and transportation, vehicle packaging and loading, food transportation scheduling, nuclear fuel transportation planning and scheduling, platform scheduling, airport gate allocation and stand planning, aircraft rescheduling, crew rostering and scheduling, nurse scheduling, personnel rostering, shift planning, maintenance planning, timetabling, and even financial planning and investment management.
There is a regular conference on the Practical Applications of
Constraint Technology, presented on
http://www.demon.co.uk/ar/PACT/