The Constraint Package

There are three types of CONSTRAINTs in the constraint package. There are constraints that are specifically for defining types of ENTITYs (main grouped by ENTITYVALUE) and there are constraints for defining certain kinds of EVENTs. Each of these constraints is a powerful tool in and of itself, but a third type of constraint gives the systems of CONSTRAINTs an even greater power: boolean logic CONSTRAINTs. The purpose of each constraint is well documented in the DataManager API.

It is important for Constraint writers to note, however, that even though the the public API method is accepts(), the appropriate method to implement in a new constraint is describes(). The mechanism for accepts() is implemented in the Kernel package. See Section 2.5 for a description of how this works and why we did it.



1999-12-13