The Extension Objects Pattern
Erich Gamma
IFA Consulting
Ceresstrasse 27
CH-8034 Zurich
gamma@ifa.ch

The Extension Objects pattern describes a way to extend a class with
additional interfaces and behaviour. It encapsulates an extension into
a separate object and provides a mechanism to negotiate for a
particular extension. The Extension Objects pattern can be applied
when you need to support the addition of new or unforeseen interfaces
to existing classes.