Issues in the design and specification of class libraries

Abstract

The design and specification of an extensible class library presents a difficult challenge: because extensibility comes from allowing the user to override parts of the implementation, more of the internal structure must be exposed to the user than in a typical procedure library. This raises issues in both how the library is designed and how its specification is written. Specification of the CLOS Metaobject Protocol required a combination of new and existing techniques to address these issues. We present those techniques, and discuss their relation to the underlying issues.