Sotirios Liaskos

On Goal-based Variability Acquisition and Analysis

We introduce a variability-intensive approach to goal decomposition that is tailored to support requirements identification for highly customizable software. The approach is based on the semantic characterization of OR-decompositions of goals. We first show that each high-level goal can be associated with a set of concerns, in response to which, alternative refinements of the goal can be introduced. A text corpus relevant to the domain of discourse can be used to derive such variability concerns that are specific to the problem. In parallel, contextual facts that can vary while a goal is being fulfilled are modeled. Then, a high-variability goal model is constructed aiming at responding to the predefined variability concerns completely, while contextual factors are used to test whether it addresses all realistic background circumstances. We apply our approach in a study from the geriatric health care domain

Requirements-driven design of autonomic application software

Autonomic computing systems reduce software maintenance costs and management complexity by taking on the responsibility for their configuration, optimization, healing, and protection. These tasks are accomplished by switching at runtime to a different system behaviour - the one that is more efficient, more secure, more stable, etc. - while still fulfilling the main purpose of the system. Thus, identifying the objectives of the system, analyzing alternative ways of how these objectives can be met, and designing a system that supports all or some of these alternative behaviours is a promising way to develop autonomic systems. This paper proposes the use of requirements goal models as a foundation for such software development process and demonstrates this on an example.

Requirements analysis for customizable software: a goals-skills-preferences framework

Software customization has been argued to benefit both the productivity of software engineers and end users. However, most customization methods rely on specialists to manually tweak individual applications for a specific user group. Existing software development methods also fail to acknowledge the importance of different kinds of user skills and preferences and how these might be incorporated into a customizable software design. We propose a framework for performing requirements analysis on user goals, skills, and preferences in order to generate a customizable software design. We illustrate our methodology with an email system and review an on-going case study involving users with traumatic brain injury.

Towards requirements-driven autonomic systems design

Autonomic computing systems reduce software maintenance costs and management complexity by taking on the responsibility for their configuration, optimization, healing, and protection. These tasks are accomplished by switching at runtime to a different system behaviour - the one that is more efficient, more secure, more stable, etc. - while still fulfilling the main purpose of the system. Thus, identifying and analyzing alternative ways of how the main objectives of the system can be achieved and designing a system that supports all of these alternative behaviours is a promising way to develop autonomic systems. This paper proposes the use of requirements goal models as a foundation for such software development process and sketches a possible architecture for autonomic systems that can be built using the this approach.

Consistency Checking of Conceptual Models via Model Merging

Requirements elicitation involves the construction of large sets of conceptual models. An important step in the analysis of these models is checking their consistency. Existing research largely focuses on checking consistency of individual models and of relationships between pairs of models. However, such strategy does not guarantee global consistency. In this paper, we propose a consistency checking approach that addresses this problem for homogeneous models. Given a set of models and a set of relationships between them, our approach works by first constructing a merged model and then verifying this model against the consistency constraints of interest. By keeping proper traceability information, consistency diagnostics obtained over the merge are projected back to the original models and their relationships. The paper also presents a set of reusable expressions for defining consistency constraints in conceptual modelling. We demonstrate the use of the developed expressions in the specification of consistency rules for class and ER diagrams, and i* goal models.

Representing and reasoning about preferences in requirements engineering

The priorities that stakeholders associate with requirements may vary from stakeholder to stakeholder and from one situation to the next. Differing priorities, in turn, imply different design decisions for the system to be. While elicitation of requirement priorities is a well-studied activity, modeling and reasoning with prioritization has not enjoyed equal attention. In this paper, we address this problem by extending a state-of-the-art goal modeling notation to support the representation of preference (“nice-to-have”) requirements. In our extension, preference goals are distinguished from mandatory ones. Then, quantitative prioritizations of the former are constructed and used as criteria for evaluating alternative ways to achieve the latter. To generate solutions, an existing preference-based planner is utilized to efficiently search for alternatives that best satisfy a given set of mandatory and preferred requirements. With such a planning tool, analysts can acquire a better understanding of the impact of high-level stakeholder preferences on low-level design decisions.

From goals to high-variability software design

Software requirements consist of functionalities and qualities to be accommodated during design. Through goal-oriented requirements engineering, stakeholder goals are refined into a space of alternative functionalities. We adopt this framework and propose a decision-making process to generate a generic software design that can accommodate the full space of alternatives each of which can fulfill stakeholder goals. Specifically, we present a process for generating complementary design views from a goal model with high variability in configurations, behavioral specifications, architectures and business processes.

Integrating Preferences into Goal Models for Requirements Engineering

Requirements can differ in their importance. As such the priorities that stakeholders associate with requirements may vary from stakeholder to stakeholder and from one situation to the next. Differing priorities, in turn, imply different design decisions for the end system. While elicitation of requirements priorities is a well studied activity, though, the modeling and reasoning side of prioritization has not enjoyed equal attention. In this paper, we address this by extending a traditional goal modeling notation to support the representation of optional and preference requirements. In our extension, optional goals are distinguished from mandatory ones. Then, quantitative prioritizations of the former are constructed and used as criteria for evaluating alternative ways to achieve the latter. A state-of-the-art preference-based planner is utilized to efficiently search for alternatives that best satisfy the given preferences. This way, analysts can acquire a better understanding of the impact of high-level stakeholder preferences to low-level design decisions.

Reverse engineering goal models from legacy code

A reverse engineering process aims at reconstructing high-level abstractions from source code. This paper presents a novel reverse engineering methodology for recovering stakeholder goal models from both structured and unstructured legacy code. The methodology consists of the following major steps: 1) Refactoring source code by extracting methods based on comments; 2) Converting the refactored code into an abstract structured program through statechart refactoring and hammock graph construction; 3) Extracting a goal model from the structured programs abstract syntax tree; 4) Identifying nonfunctional requirements and derive soft goals based on the traceability between the code and the goal model. To illustrate this requirements recovery process, we refactor stakeholder goal models from two legacy software code bases: an unstructured Web-based email in PHP (SquirrelMail) and a structured email client system in Java (Columba).

Configuring common personal software: a requirements-driven approach

We investigate the personalization capabilities of common personal software systems. We use a typical e-mail client as an example of such a system, and examine the configuration screens it offers to its users. We discover that each configuration value reflects each of the ways with which the user goals can be satisfied. Thus, we construct a goal model in which alternative ways for satisfying high level goals are matched with alternative system configurations. This way, automatic configuration of the system by reasoning about the overlaying goal model can be achieved. We find that the vast majority of the configuration options that refer to system functionality can be configured using this method, facilitating thereby the personalization tasks for users with no technical background, and ensuring, at the same time, consistency and meaningfulness in the configuration result.