Goal-Centric Traceability: Using Virtual Plumblines to Maintain Critical Systemic Qualities

Successful software development involves the elicitation, implementation, and management of critical systemic requirements related to qualities such as security, usability, and performance. Unfortunately, even when such qualities are carefully incorporated into the initial design and implemented code, there are no guarantees that they will be consistently maintained throughout the lifetime of the software system. Even though it is well known that system qualities tend to erode as functional and environmental changes are introduced, existing regression testing techniques are primarily designed to test the impact of change upon system functionality rather than to evaluate how it might affect more global qualities. The concept of using goal-centric traceability to establish relationships between a set of strategically placed assessment models and system goals is introduced. This paper describes the process, algorithms, and techniques for utilizing goal models to establish executable traces between goals and assessment models, detect change impact points through the use of automated traceability techniques, propagate impact events, and assess the impact of change upon systemic qualities. The approach is illustrated through two case studies.

1 Introduction

A plumbline is a simple yet effective tool used in the construction industry to measure whether a wall is vertically aligned. The Cambridge dictionary defines it as “a piece of string with a weight fixed to one end, which is used … to test whether something vertical, such as a wall, is exactly straigh….” As such, the plumbline provides an essential tool for measuring a fundamental, yet critical quality of a building. In much the same way, a virtual plumbline can be used to evaluate the compliance of a software-intensive system with its critical stakeholders’ goals by providing the means to assess whether system components measure up to carefully defined evaluation functions. The technique, which is named Goal-Centric Traceability (GCT), creates virtual plumblines for assessing the long-term compliance of a design and runtime system with the stakeholders’ system level goals. GCT focuses on quality goals, typically referred to as the “ilities” and specified as nonfunctional requirements (NFRs) or constraints. They represent a wide variety of attributes such as performance, reliability, safety, security, and usability, all of which can be challenging to implement and maintain correctly in a software system [7], [19].