Toward Model-Based Trade-off Analysis of Non-functional Requirements

In this paper we introduce a generic approach to analyze system design models with regard to the satisfaction of their Non-Functional Requirements (NFRs) to enable the evaluation of their NFRs´ trade-offs. NFRs and their satisfaction become especially critical and deserve more attention in certain application domains such as real-time and embedded systems. This is mainly due to the constraints and resource limitations in these systems. A design that cannot achieve the functionality of the system under these limitations can mean a failure. However, one big issue is that NFRs are interconnected and cannot be considered in isolation as they can have direct impacts on each other like security and performance. This means that a careful balance and trade-off analysis among NFRs is necessary. In doing so, the role of functional parts that contribute and are implemented to satisfy an NFR should also be taken into account. We focus on these needs and identify what information about NFRs is required in order to perform trade-off analysis and comparison of design models. We propose and explain our approach to incorporate this information into system models using UML profiling method to annotate model elements with necessary information and then calculate satisfaction values of NFRs using model transformation technique.