Visualizing Early Aspects with Use Case Maps - Transactions on Aspect-Oriented Software Development - page 135

the composition algorithm. When the next aspect is added incrementally to the
system, the original base model is used to identify the joinpoints for the new
aspect. Based on the joinpoints and the original base model, the composition
algorithm then makes further changes to the copy of the base model in order to
weave the new aspect into the system. The order in which aspects are dealt with,
however, is irrelevant for the matching and composition algorithms presented in
this paper.

5 Conclusion and Future Work

This paper is the first to discuss in detail AoUCM and algorithms for tool sup-
port. It shows how to define aspects with UCMs, presents an algorithm for
matching pointcut expressions (defined by pointcut maps) against maps in the
UCM model, presents an algorithm for composing and visualizing aspects and
the base model together, and extends the URN metamodel with aspect concepts.
Compared to other scenario-based approaches to aspect-oriented requirements
engineering, AoUCM do not require any new notational concepts, aspects can
be modeled unobtrusively, and everything can be modeled visually for an aspect,
including parameterized pointcut expressions.
No new notational concepts. AoUCM make use of the same set of modeling
elements as traditional UCMs, making it easier to switch from traditional model-
ing to aspect-oriented modeling. Most significantly, stubs are used to link advice
and pointcut expression as well as to visualize the composed system. Jacobson
and Ng [25] add the concept of pointcut to use case modeling and change the
meaning of extension points. Moreira et al. [12, 28, 29] require several extensions
to UML diagrams in order to visualize aspects. Zdun and Strembeck [42] add
start and end nodes for aspects. Whittle and Araujo [13, 41], de Bruin and van
Vliet [22], as well as Barros and Gomes [15], however, do not require changes to
modeling notations (note that stereotyping does not really change the modeling
notation).
Modeled unobtrusively. AoUCM allow aspects to be defined without influ-
encing the base model as parameterized pointcut expressions are linked with the
base through a matching algorithm. This is a crucial point of aspect-orientation
often referred to as obliviousness as the base model must not be polluted by
aspect-specific information. Jacobson and Ng violate this point by requiring ex-
tension points to be defined in the base. Similarly, de Bruin and van Vliet require
Pre and Post stubs to be added to the base model. All other techniques men-
tioned in the paragraph above, however, model aspects also unobtrusively. Note
that the approach by Zdun and Strembeck is not applicable to this category
because it is not concerned with defining aspects but visualizing the composed
system only.
Visual aspects (including parameterized pointcuts). AoUCM can model
visually every part of an aspect including parameterized pointcuts, therefore
avoiding a modeling paradigm break. Visual models are usually the preferred