Constraints in concurrent object-oriented environment

A constraint is a numeric or geometric relationship between objects. Constraints have a declarative nature. Constraints are a natural way for describing relationships between objects. Combining constraint systems and object-oriented programming (OOP) appears hard. All existing systems implicitly compromise the encapsulation principle of OOP. This paper proposes a mechanism that provides for constraints in an object-oriented environment. Constraints are triggered by messages that are being sent to objects. Constraints are resolved through local propagation of known state. We claim that this is the most practical technique in a concurrent or parallel object environment. No compromise has been made to the OOP paradigm. Therefore a truly object-oriented approach to constraint programming is the result.