Atlas: A Case Study in Building a Web-Based Learning Environment Using Aspect-oriented Programming

The Advanced Teaching and Learning Academic Server (Atlas) is a software system that supports web-based learning. Students can register for courses, and can navigate through personalized views of course material. Atlas has been built according to Sun Microsystem's Java (TM) Servlet specification using Xerox PARC's aspect-oriented programming support called AspectJ (TM). Since aspect-oriented programming is still in its infancy, little experience with employing this paradigm is currently available. In this paper, we start filling this gap by describing the aspects we used in Atlas and by discussing the effect of aspects on our object-oriented development practices. We describe some rules and policies that we employed to achieve our goals of maintainability and modifiability, and introduce a straightforward notation to express the design of aspects. Although we faced some small hurdles along the way, this combination of technology helped us build a fast, well-structured system in a reasonable amount of time.