João Pimentel

Deriving software architectural models from requirements models for adaptive systems: the STREAM-A approach

Some quality attributes are known to have an impact on the overall architecture of a system, so that they are required to be properly handled from the early beginning of the software development. For example, adaptability is a key concern for autonomic and adaptive systems, which brings to them the capability to alter their behavior in response to changes on their surrounding environments. In this paper, we propose a Strategy for Transition between Requirements and Architectural Models for Adaptive systems (STREAM-A). In particular, we use goal models based on the i* (i-Star) framework to support the design and evolution of systems that require adaptability. To obtain software architectures for such systems, the STREAM-A approach uses model transformations from i* models to architectural models expressed in Acme. Both the requirements and the architectural model are refined to accomplish the adaptability requirement.

Requirements and architectural approaches to adaptive software systems: a comparative study

The growing interest in adaptive software systems has resulted in a number of different proposals for the design of adaptive systems. Some approaches adopt architectural models, whereas others model adaptation options, at the level of requirements. This dichotomy has motivated us to perform a comparative study between two proposals for the design of adaptive systems: the Rainbow Framework (architecture-based) and our own proposal, Zanshin (requirements-based). This evaluation paper reports on our methodology and results. It also provides a comparison between the use of architectural and requirements models as centrepieces of adaptation, offering guidelines for the future research in the field of adaptive systems.

Changing attitudes towards the generation of architectural models

Architectural design is an important activity, but the understanding of how it is related to requirements modeling is rather limited. It is worth noting that goal orientation is an increasingly recognized paradigm for eliciting, modeling, specifying, and analyzing software requirements. However, it is not clear how goal models are related to architectural models. In this paper we present an approach based on model transformations to derive architectural structural specifications from system goals. The source and target languages are respectively the i* (iStar) modeling language and the Acme architectural description language. A real case study is used to show the feasibility of our approach.

Configuring the Variability of Business Process Models Using Non-Functional Requirements

The existence of variations in the organizational environment makes the configuration of business process models a complex activity, even for experienced business analysts. The increasing adoption of business processes models by software engineers as a input for requirements analysis strengthens the importance of adressing this issue. The challenge is to configure business processes to fit the organization better. We propose an approach that combines variability analysis and non-functional requirements to drive the configuration of a business process. Applying this approach we can analyze variability in the model in order to assess the impact of the choices on the process quality constraints - the non-functional requirements. Moreover, it provides a rationale for the selection of a specific configuration.

From i* Requirements Models to Conceptual Models of a Model Driven Development Process

A good understanding of the systems requirements has a high impact in the successful development of software products. Therefore, an appropriate requirements model must provide a comprehensive structure for what must be elicited, evaluated, specified, consolidated, and modified, instead of just providing facilities for software specifications. Since there is a well-known gap between requirements specifications and final software products, we propose the integration of Goal-Oriented Requirements Engineering (GORE) and Model-Driven Development (MDD) to solve this gap. The core of our proposal is comprised by a set of guidelines to automate the process of going from an initial i* model to a final software product by means of a precise model transformation process. Finally, we use a case study that is based on a photographic agency system in order to illustrate our approach.

Taking goal models downstream: A systematic roadmap

Creating and reasoning with goal models is useful for capturing, understanding, and communicating about requirements in the early stages of information system (re)development. However, the utility of goal models is greatly enhanced when an awareness of system intentions can feed into other stages in the requirements analysis process (e.g. requirements elaboration, validation, planning), and can be used as part of the entire system life cycle (e.g., architecture, process design, coding, testing, monitoring, adaptation, and evolution). In order to understand the progress that has been made in integrating goal models with downstream system development, we ask: what approaches exist which map/integrate/transform goal-oriented languages to other software artifacts or languages? To answer this question, we conduct a systematic survey, producing a roadmap of work summarizing 174 publications. Results include a categorization of the “why?” and “how?” for each approach. Findings show that there are a wide variety of proposals with many proposed sources and targets, covering multiple paradigms, motivated by a variety of purposes. We conclude that although much work has been done in this area, the work is fragmented and is often still in a proposal stage.

A Model Transformation Approach to Derive Architectural Models from Goal-Oriented Requirements Models

Requirements engineering and architectural design are key activities for successful development of software systems. Both activities are strongly intertwined and interrelated, but many steps toward generating architecture models from requirements models are driven by intuition and architectural knowledge. Thus, systematic approaches that integrate requirements engineering and architectural design activities are needed. This paper presents an approach based on model transformations to generate architectural models from requirements models. The source and target languages are respectively the i* modeling language and Acme architectural description language (ADL). A real web-based recommendation system is used as case study to illustrate our approach.

Goal-Driven Adaptation of Service-Based Systems from Runtime Monitoring Data

Service-based systems need to provide flexibility to adapt both to evolving requirements from multiple, often conflicting, ephemeral and unknown stakeholders, as well as to changes in the runtime behavior of their component services. Goal-oriented models allow representing the requirements of the system whilst keeping information about alternatives. We present the MAESoS approach which uses i* diagrams to identify quality of service requirements over services. The alternatives are extracted and kept in a variability model. A monitoring infrastructure identifies changes in runtime behavior that can propagate up to the level of stakeholder goals and trigger the required adaptations. We illustrate the approach with a scenario of use.

Towards anticipating requirements changes through studies of the future

Whilst it is considered a good practice to focus Requirements Engineering on current stakeholder needs, the high costs implied by requirements changes and the emergence of the Autonomic Computing paradigm raised the need for dealing with issues that are not currently requirements but that may come to be in the future. This work shows how foresight techniques can be used for requirements elicitation, and discusses the impacts of studying the future to that requirements engineering activity. In particular, it addresses the use of the Futures Wheel method to enrich goal models.

From requirements to statecharts via design refinement

The derivation of statecharts from requirements has been addressed from many perspectives. All of them assume that the derivation process is a linear series of refinements resulting in a single statechart, thereby missing the opportunity to explore alternatives in the design space. We propose a multi-dimensional approach that exploits inherent variability of the design space, where alternative refinements are considered for the same intermediate problem, resulting in multiple solutions (statecharts) from a single initial problem (requirements). In order to accomplish this, we propose an extended form of goal model where architects can incrementally refine the original requirements by considering behavioral alternatives leading to design solutions. The proposed refinement process is illustrated through an example from the literature. Experimentation with randomly generated models suggests that the proposal is scalable.