Consistent Change Propagation in Software Design Models

Design models describe different viewpoints of a software system separating functionality, from structure, behavior, or usage. While these models are meant to be separate in their description, they are nonetheless related by manifold dependencies. After all, they describe the same system. It is necessary to understand this network of dependencies to understand how the various models are connected. Yet, this network of dependencies is also the most significant reason for failure during software modeling. It is the root cause for failure to propagate changes correctly and completely. Although change propagation as a whole is a daunting challenge to tackle, this proposed work suggests an approach for solving this problem in context of software models. In context of such models, incorrect or incomplete changes are detectable if these changes cause inconsistencies among the models involved. This proposed work thus builds on technology we pioneered under a predecessor project (FWF project P21321- N15 titled "Inconsistencies and their Impact on Software Design Models"). That project developed a methodology for understanding how inconsistencies are caused and what changes can repair them. That predecessor project is now in its final stages and this proposed work will build on its results to develop a methodology for change propagation in software design models. Models change continuously and if a change is not correctly applied to all models of a software system then inconsistencies are caused. Since there are often near infinite choices for repairing inconsistencies, this project will tailor the repairing of inconsistencies by not seeing inconsistencies in isolation but by understanding the cumulative effect of changes over time (during propagation). The basic observation is that change propagation may cause further inconsistencies and their repair should not contradict earlier changes. This simple idea forms the basis for understanding relationships among inconsistencies which in turn helps us explore the computationally expensive space of change combinations based on a novel idea that is analogous to triangulation. This work will 1) research the methodology for change propagation across arbitrary design models governed by constraints, 2) develop a proof-of-concept tool to demonstrate the approach, and 3) evaluate the methodology and tool on industrial models available to us. As we did in the predecessor project, we will continue to publish the research results in the best peer-reviewed journals and conferences; and pursuit its transition to industrial use. This proposal requests funding for two PhD students and one Master`s student only plus their travel needs.

Software models let engineers describe systems from different points of views. This has the benefit that engineers can separate the modeling of different parts of systems, different domains, or even different functionality. However, these different models do have to fit together and today many consistency rules exist that let engineers define relationships among models. Consistent change propagation is then simply about the ability to propagate changes among these software models without causing (further) inconsistencies. If an engineer changes a model then this change may cause inconsistencies with other models if the change was not carried through correctly and completely. An inconsistency in this case is not an error but rather a symptom for incomplete change propagation. Resolving such inconsistencies (by repairing them) is then equivalent to continuing the change propagation. The problem of incomplete change propagation has been a significant contributor to many high profile engineering failures. This project showed that consistent change propagation is feasible and is applicable to a wide range of engineering domains. We demonstrated this on model/meta model co-evolution, the consistent merging of models, and software/systems evolution in other domains.