Delta Changes for OO Software Adaptation: Pervasive or Invasive?

The ability for software products to adapt to future changes is essential. Whether the change, the delta, is prefixed to subclasses or postfixed to super classes, class hierarchies grow vertically, upward or downward. The horizontal expansions (infix changes) of these hierarchies have been restricted or neglected. The infix changes are better understood as crosscutting concerns. However, these concerns shall not be confused with mixins in OO technology. Although OO and AOP technologies have addressed the issue of the incremental addition to software products, the mix-and-match of software features often results in a redundant code and class hierarchies that are difficult to integrate and maintain. In this paper we present an approach that combines the advantages in both AspectJ for its join semantics and HyperJ for its merge and provides an XML-based weaving rules to incorporate the delta changes into the core class hierarchies both dynamically and statically.