The constraint-based paradigm: integrating object-oriented and rule-based programming

The authors introduce a novel formalism that combines the object-oriented and rule-based paradigms in an elegant and orthogonal way. The constraint-based model is a generalization of traditional object-oriented paradigms and is based on three orthogonal subparadigms. The first is constraint-based invocation, which is a generalization of the traditional invocation where dispatch is done based on the types of the arguments. In constraint-based invocation, dispatch is done based on constraints that are arbitrary user-defined predicates. The second subparadigm is instance inheritance, a dual to the concept of class inheritance in the sense that class inheritance structures classes and instance inheritance structures instances. The third is procedural attachments (also known as active values or access-oriented programming), where a function is called in a data-driven manner. The semantics of this concept are generalized to all objects in the constraint-based model. A central philosophical argument is that so-called multiparadigm languages should be developed not by combination of paradigms in a partially integrated system, but by their synergistic unification under a new, subsuming paradigm