Predicates and Directives for a Parametric-associative Matching Mechanism for Shapes and Shape Grammars

Abstract

Predicates and directives are proposed to extend the versatility and expressivity of a shape rule specification `language'. Specifically, a predicate serves to xpress a condition on the application of a parametric-associative shape rule that cannot simply be explicated within the left-hand side shape. A directive, on the other hand, is a value specification that is required when applying a parametric-associative shape rule, where this value specification cannot be derived from or expressed within the right-hand-side shape. We discuss the benefits of a set of predicates and directives to address seemingly simple requests that might actually be hard to express otherwise. Specifically, we elaborate on the motivation for introducing predicates and directives, and demonstrate the various predicates and directives in more detail, including their implementation.