Performing Projection in Problem Frames Using Scenarios

In the Problem Frames (PF) approach there are five basic problem frames and some variants to them. When a problem is being analysed, it is initially matched against these frames. If the problem does not fit into the basic problem frames or their variants, then problem analysis is performed. It has been recognised that `projection´ is an effective technique for analysing problems. That is, each sub-problem is considered as a projection of the main problem concerned only with the phenomena relevant to that sub-problem. The PF approach lacks a precise definition of problem projection and does not provide specific instructions on how to perform this projection. In this paper, we use the concept of projection from relational algebra and combine it with concepts from the PF and scenario-based approaches to present a conceptual model for conducting problem projection in requirements engineering. This model and ontology extend problem description at scenario level and support systematic derivation of sub-problems from scenarios. We also provide a detailed process description for performing projection for problem analysis and present the utility of our approach with a case study.