Aspect-specification based on structural type information

Aspects developed in aspect-oriented systems often need to hook onto multiple objects that share common structural characteristics - such as attributes and operations. In strongly-typed aspect-oriented systems like AspectJ these objects need to be of common type so that pointcuts may designate them and pieces of advice may interact with them. Such type-systems are typically based on nominal types, therefore, aspects cannot interact with objects according to their structural information in a common way. This paper argues that specifying aspects based on a nominal type system is not sufficient and shows that aspect-specifications based on structural characteristics overcome this problem. A corresponding extension of the nominal type systems is proposed and illustrated by means of structural types and compound types.