GenVoca generators synthesize software systems by composing components from reuse libraries. GenVoca components are designed to export and import standardized interfaces, and thus be plug-compatible, interchangeable, and interoperable with other components. We examine two different but important issues in software system synthesis. First, not all syntactically correct compositions of components are semantically correct. We present simple, efficient, and domain-independent algorithms for validating compositions of GenVoca components. Second, components that export and import immutable interfaces are too restrictive for software system synthesis. We show that the interfaces and bodies of GenVoca components are subjective, i.e., they mutate and enlarge upon instantiation. This mutability enables software systems with customized interfaces to be composed from components with "standardized" interfaces.

Generators synthesize software systems by composing components from reuse libraries. In general, not all syntactically correct compositions are semantically correct. We present domain independent algorithms for the GenVoca model of software generators to validate component compositions. Our work relies on attribute grammars and offers powerful debugging capabilities with explanation based error reporting. We illustrate our approach by showing how compositions are debugged by a GenVoca generator for container data structures.