1. A method of representing model-operative patterns, comprising: specifying a pattern codification for a particular pattern, the pattern codification comprising a structural definition portion and a behavioral definition portion, wherein: the pattern codification for the particular pattern is decoupled from executable code that carries out each operation for implementing the particular pattern; the structural definition portion defines each of at least one role used in the particular pattern and each of at least one relationship used in the particular pattern, wherein each of the at least one relationship involves at least one of the at least one role; when the particular pattern is composed from other composited patterns, the behavioral definition portion specifies each of at least one constraint that must be met before the particular pattern can be applied and identifies how to use ones of the at least one role of the particular pattern and the at least one relationship of the particular pattern for constraining expressions that are defined using at least one role and at least one relationship of the other composited patterns; and when the particular pattern is not composed from other composited patterns, the behavioral definition portion identifies the executable code that carries out each of at least one operation to invoke for implementing the particular pattern when the particular pattern is applied; comprehending the particular pattern in a particular model by identifying elements of the model that are candidate participants for each of the at least one pattern role of the particular pattern, for each of the at least one relationship involving the each role; executing a pattern operation using the comprehended pattern to determine whether each of the at least one constraint of the particular pattern is met; and responsive to determining that each of the at least one constraint is met, concluding that the identified elements of the model together comprise an occurrence of the particular pattern.