A goal-oriented approach for the generation and evaluation of alternative architectures

There is a recognized gap between requirements and architectures. There is also evidence that architecture evaluation, when done at the early phases of the development lifecycle, is an effective way to ensure the quality attributes of the final system. As quality attributes may be satisfied at a different extent by different alternative architectural solutions, an exploration and evaluation of alternatives is often needed. In order to address this issue at the requirements level, we propose to model architectures using the i* framework, a goal-oriented modelling language that allows to represent the functional and non-functional requirements of an architecture using actors and dependencies instead of components and connectors. Once the architectures are modelled, we propose guidelines for the generation of alternative architectures based upon existing architectural patterns, and for the definition of structural metrics for the evaluation of the resulting alternative models. The applicability of the approach is shown with the Home Service Robot case study.Peer ReviewedPostprint (author's final draft

A metrics definition framework for i*

Measuring is a central task in the any engineering discipline, and modelling is not an exception. The need for measuring properties over i* models arises in different contexts. We have analysed this need over i* models of organizations, projects, systems and architectures. As a result, we have proposed a framework which includes: (a) a metamodel of i* that defines the elements that build the model; (b) a framework for the definition of metrics; (c) a collection of metrics (currently under construction) of different nature built with the framework. In this work, we present these basic concepts and discuss the applicability of the approach.Peer ReviewedPostprint (published version

On the adequacy of i* models for representing and analyzing software architectures

In order to work at the software architecture level, specification languages and analysis techniques are needed. There exist many proposals that serve that purpose, but few of them address architecture and requirements altogether, leaving a gap between both disciplines. Goal-oriented approaches are suitable for bridging this gap because they allow representing architecture-related concepts (components, nodes, files, etc.) and more abstract concepts (goals, non-functional requirements, etc.) by using the same constructs. In this paper we explore the suitability of the i* goal-oriented approach for representing software architectures. For doing so, we check its properties against the ones suitable for Architecture Description Languages and we define some criteria for solving the unfulfilled aspects in representing the architectures. This paper assumes basic notions on i*.Peer ReviewedPostprint (author's final draft

Style-Based Model Transformation for Early Extrafunctional Analysis of Distributed Systems

International audienceIn distributed environments, client-server, publish-subscribe, and peer-to-peer architecture styles are largely employed. However, style selection often remains implicit, relying on the designer's know-how regarding requirements. In this paper, we propose a framework to explicitly specify distributed architectural styles, as independent models of the application functionalities. To justify feasibility and further benefits of our approach, we formally define three classical distributed architectural styles in a process calculus. Our proposal then opens up the way to a systematic composition of functional models with architectural style models as an endogenous transformation. Comparative analysis of extrafunctional properties could then be proposed at the early design stages to guide the architect in stylistic choices

i* in practice: identifying frequent problems in its application

Several notations have been proposed in the last decades to support information system architecting, design and implementation. Although some of them have been widely adopted, their practical application remains cumbersome. Reasons are manifold: ambiguous semantics, confusing graphical representation, lack of safe guidelines, etc. In this paper, we explored the use of the i* framework in industry for modeling organizational context. We review the models resulting from 36 industrial collaborations conducted in the last five years, where i* has been intensively used by novice modellers, without previous exposure to i*, acting as junior consultants in the organizations. We identify and categorize the main problems that they faced and as a result, we propose a set of guidelines to improve the adoption and practical application of the framework.Peer ReviewedPostprint (author's final draft

An i*-based Reengineering Framework for Requirements Engineering

Avui en dia, els sistemes d'informació són un actiu clau en les organitzacions i sovint els proporcionen un avantatges competitiu. Per a que això segueixi així, han de ser mantinguts i evolucionats d'acord amb els objectius estratègics de la organització. Aquesta evolució inclou els requeriments del sistema d'informació, la tecnologia emprada i els processos suportats. L'impacte dels canvis pot anar des de petites modificacions al desenvolupament d'un nou sistema d'informació i, per aquest motiu, l'evolució dels sistemes d'informació s'analitza durant la fase de requeriments, on es possible avaluar-ne la magnitud utilitzant menys recursos. Des d'aquest punt de vista, els mètodes de l'enginyeria de requeriments i els de la reenginyeria de processos sovint comparteixen els mateixos objectius i es pot considerar que la reenginyeria de processos es adequada tant per al desenvolupament com per al manteniment dels sistemes d'informació. El llenguatge i* està orientat a objectius i permet modelar els sistemes d'informació en termes d'actors i dependencies entre ells. El llenguatge i* s'utilitza en l'enginyeria de requeriments i en la reenginyeria de processos de negoci, però no existeixen gaires propostes comunes a ambdues disciplines. Amb l'objectiu d'utilitzar el llenguatge i* en la reenginyeria de processos, s'ha definit PRiM, un mètode basat en i* per a la reenginyeria de processos (Proces Reenginieering i*-based Method). PRiM assumeix que ja existeix un procés que s'utilitzarà com a punt de partida per l'especificació o l'evolució del nou sistema d'informació. El mètode PRiM consta de sis fases: 1) l'anàlisi dels processos i dels sistemes d'informació actuals, 2) la construcció del model i*, 3) la reenginyeria dels processos actuals, 4) la generació de models i* representant les diferents alternatives, 5) l'avaluació de les alternatives utilitzant mètriques estructurals i 6) l'especificació del nou sistema d'informació a partir del model i* escollit. En les sis fases de PRiM, s'utilitzen diferents mètodes i tècniques algunes creades expressament pel mètode i d'altres provinents de l'enginyeria de requeriments i la reenginyeria de processos. Tot i això, hi ha altres mètodes i tècniques que poden ser utilitzades enlloc d'aquestes i que poden ser mes convenients quan les condicions d'aplicació del mètode canvien. Per tal de permetre la selecció i inclusió d'altres tècniques, es proposa l'aplicació de l'enginyeria de mètodes (Method Engineering). Aquesta disciplina permet construir nous mètodes a partir de parts de mètodes ja existents, i s'ha utilitzat per definir un mètode marc per a la reenginyeria anomenat ReeF (Reengineering Framework). A ReeF, les sis fases de PRiM es presenten de forma genèrica per tal de permetre la selecció de la tècnica més apropiada per cada una de les fases, a partir de l'experiència de l'usuari com dels seus coneixements de l'aplicació. Com a exemple d'aplicació de ReeF, s'ha definit el mètode SARiM.Les contribucions principals de la tesis son dues. En primer lloc, els dos mètodes basats en i* definits (PRiM per a la reenginyeria de processos, i SARiM, per a la reenginyeria d'arquitectures software). En segon lloc, les diferents tècniques i* definides en PRiM i que poden ser utilitzades per construir models i*, generar alternatives i avaluar-les amb mètriques estructurals. Aquestes tècniques i mètodes s'han obtingut a partir de l'estudi de l'estat de l'art i s'han validat en diferents casos d'estudi formatius i en un cas d'estudi industrial. Com a suport, s'han desenvolupat dues eines: 1) REDEPEND-REACT, que permet la modelització gràfica de models i*, la generació d'alternatives i la definició de mètriques estructurals, i 2) J-PRiM, que dóna suport a les fases de PRiM mitjançant el tractament textual dels models i*.Information Systems are a crucial asset of the organizations and can provide competitive advantages to them. However, once the Information System is built, it has to be maintained and evolved, which includes changes on the requirements, the technology used, or the business processes supported. All these changes are diverse in nature and may require different treatments according to their impact, ranging from small improvements to the deployment of a new Information System. In both situations, changes are addressed at the requirements level, where decisions are analysed involving less resources. Because Requirements Engineering and Business Process Reengineering methods share common activities, and the design of the Information System with the business strategy has to be maintained during its evolution, a Business Process Reengineering approach is adequate for addressing Information Systems Development when there is an existing Information System to be used as starting point. The i* framework is a well-consolidated goal-oriented approach that allows to model Information Systems in a graphical way, in terms of actors and dependencies among them. The i* framework addresses Requirements Engineering and Business Process Reengineering but none of the i*-based existing approaches provides a complete framework for reengineering. In order to explore the applicability of i* for a reengineering framework, we have defined PRiM: a Process Reengineering i* Method, which assumes that there is an existing process that is the basis for the specification of the new Information System. PRiM is a six-phase method that combines techniques from the fields of Business Process Reengineering and Requirements Engineering and defines new techniques when needed. As a result PRiM addresses: 1) the analysis of the current process using socio-technical analysis techniques; 2) the construction of the i* model by differentiating the operationalization of the process form the strategic intentionality behind it; 3) the reengineering of the current process based on its analysis for improvements using goal acquisition techniques; 4) the generation of alternatives based on heuristics and patterns; 5) the evaluation of alternatives by defining structural metrics; and, 6) the specification of the new Information System from the selected i* model.There are several techniques from the Requirements Engineering and Business Process Reengineering fields, that can be used instead the ones selected in PRiM. Therefore, in order to not enforce the application of a certain technique we propose a more generic framework where to use and combine them. Method Engineering is the discipline that constructs new methods from parts of existing ones and, so, it is the approach adopted to define ReeF: a Reengineering Framework. In ReeF the six phases of PRiM are abstracted and generalized in order to allow selecting the most appropriate techniques for each of the phases, depending on the user expertise and the domain of application. As an example of the applicability of ReeF, the new method SARiM is defined. The main contributions of this work are twofold. On the one hand, two i*-based methods are defined: the PRiM method, which addresses process reengineering, and SARiM, which addresses software architecture reengineering. On the other hand, we provide several i*-based techniques to be used for constructing i* models, generating alternatives, and evaluating them using Structural Metrics. These methods and techniques are based on exhaustive review of existing work and their validation is done by means of several formative case studies and an industrial case study. Tool support has been developed for the approach: REDEPEND-REACT supporting the graphical modelling of i*, the generation of alternatives and the definition of Structural Metrics; and J-PRiM supporting all the phases of the PRiM method using a textual visualization of the i* models

Quality Goal Oriented Architectural Design and Traceability for Evolvable Software Systems

Softwaresysteme werden heute z.B. aufgrund sich ändernder Geschäftsprozesse oder Technologien mit häufigen Veränderungen konfrontiert. Die Software und speziell ihre Architektur muss diese Änderungen zur dauerhaften Nutzbarkeit ermöglichen.Während der Software-Evolution können Änderungen zu einer Verschlechterung der Architektur führen, der Architekturerosion. Dies erschwert oder verhindert weitere Änderungen wegen Inkonsistenz oder fehlendem Programmverstehen. Zur Erosionsvermeidung müssen Qualitätsziele wie Weiterentwickelbarkeit, Performanz oder Usability sowie die Nachvollziehbarkeit von Architekturentwurfsentscheidungen berücksichtigt werden. Dies wird jedoch oft vernachlässigt.Existierende Entwurfsmethoden unterstützen den Übergang von Qualitätzielen zu geeigneten Architekturlösungen nur unzureichend aufgrund einer Lücke zwischen Methoden des Requirements Engineering und des Architekturentwurfs. Insbesondere gilt dies für Weiterentwickelbarkeit und die Nachvollziehbarkeit von Entwurfsentscheidungen durch explizite Modellabhängigkeiten.Diese Arbeit präsentiert ein neues Konzept, genannt Goal Solution Scheme, das Qualitätsziele über Architekturprinzipien auf Lösungsinstrumente durch explizite Abhängigkeiten abbildet. Es hilft somit, Architekturlösungen entsprechend ihrem Einfluss auf Qualitätsziele auszuwählen. Das Schema wird speziell hinsichtlich Weiterentwickelbarkeit diskutiert und ist in ein zielorientiertes Vorgehen eingebettet, das etablierte Methoden und Konzepte des Requirements Engineering und Architekturentwurfs verbessert und integriert. Dies wird ergänzt durch ein Traceability-Konzept, welches einen regelbasierten Ansatz mit Techniken des Information Retrieval verbindet. Dies ermöglicht eine (halb-) automatische Erstellung von Traceability Links mit spezifischen Linktypen und Attributen für eine reichhaltige Semantik sowie mit hoher Genauigkeit und Trefferquote.Die Realisierbarkeit des Ansatzes wird an einer Fallstudie einer Software für mobile Serviceroboter gezeigt. Das Werkzeug EMFTrace wurde als eine erweiterbare Plattform basierend auf Eclipse-Technologie implementiert, um die Anwendbarkeit der Konzepte zu zeigen. Es integriert Entwurfsmodelle von externen CASE-Tools mittels XML-Technologie in einem gemeinsamen Modell-Repository, wendet Regeln zur Linkerstellung an und bietet Validierungsfunktionen für Regeln und Links.Today software systems are frequently faced with demands for changes, for example, due to changing business processes or technologies. The software and especially its architecture has to cope with those frequent changes to permanently remain usable.During software evolution changes can lead to a deterioration of the structure of software architectures called architectural erosion, which hampers or even inhibits further changes because of inconsistencies or lacking program comprehension. To support changes and avoid erosion, especially quality goals, such as evolvability, performance, or usability, and the traceability of design decisions have to be considered during architectural design. This however often is neglected.Existing design methods do not sufficiently support the transition from the quality goals to appropriate architectural solutions because there is still a gap between requirements engineering and architectural design methods. Particularly support is lacking for the goal evolvability and for the traceability of design decisions by explicit model dependencies.This thesis presents a new concept called Goal Solution Scheme, which provides a mapping from goals via architectural principles to solution instruments by explicit dependencies. Thus it helps to select appropriate architectural solutions according to their influence on quality goals. The scheme is discussed especially regarding evolvability, and it is embedded in a goal-oriented architectural design method, which enhances and integrates established methods and concepts from requirements engineering as well as architectural design. This is supplemented by a traceability concept, which combines a rule-based approach with information retrieval techniques for a (semi-) automated establishment of links with specific link types and attributes for rich semantics and a high precision and recall.The feasibility of the design approach has been evaluated in a case study of a software platform for mobile robots. A prototype tool suite called EMFTrace was implemented as an extensible platform based on Eclipse technology to show the practicability of the thesis' concept. It integrates design models from external CASE tools in a joint model repository by means of XML technology, applies rules for link establishment, and provides validation capabilities for rules and links

A Goal-Oriented Approach for the Generation and Evaluation of Alternative Architectures

Abstract. There is a recognized gap between requirements and architectures. There is also evidence that architecture evaluation, when done at the early phases of the development lifecycle, is an effective way to ensure the quality attributes of the final system. As quality attributes may be satisfied at a different extent by different alternative architectural solutions, an exploration and evaluation of alternatives is often needed. In order to address this issue at the requirements level, we propose to model architectures using the i * framework, a goal-oriented modelling language that allows to represent the functional and non-functional requirements of an architecture using actors and dependencies instead of components and connectors. Once the architectures are modelled, we propose guidelines for the generation of alternative architectures based upon existing architectural patterns, and for the definition of structural metrics for the evaluation of the resulting alternative models. The applicability of the approach is shown with the Home Service Robot case study.

A goal-oriented approach for the generation and evaluation of alternative architectures

There is a recognized gap between requirements and architectures. There is also evidence that architecture evaluation, when done at the early phases of the development lifecycle, is an effective way to ensure the quality attributes of the final system. As quality attributes may be satisfied at a different extent by different alternative architectural solutions, an exploration and evaluation of alternatives is often needed. In order to address this issue at the requirements level, we propose to model architectures using the i* framework, a goal-oriented modelling language that allows to represent the functional and non-functional requirements of an architecture using actors and dependencies instead of components and connectors. Once the architectures are modelled, we propose guidelines for the generation of alternative architectures based upon existing architectural patterns, and for the definition of structural metrics for the evaluation of the resulting alternative models. The applicability of the approach is shown with the Home Service Robot case study.Peer Reviewe