Requirements analysis of the VoD application using the tools in TRADE

This report contains a specification of requirements for a video-on-demand (VoD) application developed at Belgacom, used as a trial application in the 2RARE project. The specification contains three parts: an informal specification in natural language; a semiformal specification consisting of a number of diagrams intended to illustrate the informal specification; and a formal specification that makes the requiremants on the desired software system precise. The informal specification is structured in such a way that it resembles official specification documents conforming to standards such as that of IEEE or ESA. The semiformal specification uses some of the tools in from a requirements engineering toolkit called TRADE (Toolkit for Requirements And Design Engineering). The purpose of TRADE is to combine the best ideas in current structured and object-oriented analysis and design methods within a traditional systems engineering framework. In the case of the VoD system, the systems engineering framework is useful because it provides techniques for allocation and flowdown of system functions to components. TRADE consists of semiformal techniques taken from structured and object-oriented analysis as well as a formal specification langyage, which provides constructs that correspond to the semiformal constructs. The formal specification used in TRADE is LCM (Language for Conceptual Modeling), which is a syntactically sugared version of order-sorted dynamic logic with equality. The purpose of this report is to illustrate and validate the TRADE/LCM approach in the specification of distributed, communication-intensive systems

Verified System Development with the AutoFocus Tool Chain

This work presents a model-based development methodology for verified software systems as well as a tool support for it: an applied AutoFocus tool chain and its basic principles emphasizing the verification of the system under development as well as the check mechanisms we used to raise the level of confidence in the correctness of the implementation of the automatic generators.Comment: In Proceedings WS-FMDS 2012, arXiv:1207.184

Mixing Formal and Informal Model Elements for Tracing Requirements

Tracing between informal requirements and formal models is challenging. A method for such tracing should permit to deal efficiently with changes to both the requirements and the model. A particular challenge is posed by the persisting interplay of formal and informal elements. In this paper, we describe an incremental approach to requirements validation and systems modelling. Formal modelling facilitates a high degree of automation: it serves for validation and traceability. The foundation for our approach are requirements that are structured according to the WRSPM reference model. We provide a system for traceability with a state-based formal method that supports refinement. We do not require all specification elements to be modelled formally and support incremental incorporation of new specification elements into the formal model. Refinement is used to deal with larger amounts of requirements in a structured way. We provide a small example using Problem Frames and Event-B to demonstrate our approach

Scrum Abandonment in Distributed Teams: A Revelatory Case

The last decade has witnessed substantial growth in the adoption of both Agile and distributed software development. However, combining Agile practices, which emphasize regular informal communication, with geographically and temporally distributed sites, which hinder regular informal communication, presents numerous challenges. Proponents of Agile, especially the Scrum project management framework, have published several case studies of successful Scrum implementations in distributed environments. However, few empirical studies examine failed or abandoned Scrum implementations. Consequently, this paper presents a revelatory case study of a geographically and temporally distributed software development team that abandoned its attempted transition to Scrum. Two factors associated with the team’s decision to abandon Scrum are identified – degradation of Scrum practices due to distribution and the undermining of the ScrumMaster’s credibility. Based on this analysis the paper proposes that task/team familiarity, group cohesion and transactive memory may be combined to understand the relationship between geotemporal distribution, process and performance

The engineering roles of requirements and specification

The distinction between requirements and specification is often confused in practice. This obstructs the system validation process, because it is unclear what exactly should be validated, and against what it should be validated. The reference model of Gunter et al. addresses this difficulty by providing a framework within which requirements can be distinguished from specification. It separates world phenomena from machine phenomena. However, it does not explain how the characterization can be used to help assure system validity. In this paper, we enhance the reference model to account for certain key elements that are necessary to expose and clarify the distinction and the link between requirements and specification. We use the enhanced version to present a more refined picture of validity, where validation has two steps that can be undertaken separately. We use this picture to question whether the “what the system will do, not how it will do it ” paradigm is useful in describing how to construct a specification, and propose an alternative. Finally, we present the requirements and specification for an illustrative example based on a runway incursion prevention system, with the ArchiTRIO formal language in a UML-like environment, to show how this might be done in practice.

Un modelo para documentar la elicitación de requisitos

Context: This work proposes a model to document the elicitation of requirements in the field of Requirements Engineering. Method: A systematic review of the literature was conducted to determine the validity and effectiveness of the existing models for documenting requirements elicitation. Results: By analyzing the results of this review, it was concluded that it is possible – and that is required – to take the best documented practices and add principles from logic, abstraction, and formal methods to them in order to structure a semi-formal model for documenting elicitation. Those currently proposed focus on techniques to collect information and pay little attention to documentation. In addition, these models are mainly based on natural language, which makes their interpretation difficult, and they generate re-processing in later stages of the life cycle due to ambiguities. Conclusions: This article describes a structured model, as well as its application and validation, by comparing it against five models found in the review.Contexto: En este trabajo se propone un modelo para documentar la elicitación de requisitos en el área de Ingeniería de Requisitos. Método: Se realizó una revisión sistemática de la literatura para determinar la validez y efectividad de los modelos que existen para documentar la elicitación de requisitos. Resultados: Analizando los resultados de esta revisión, se concluyó que es posible –y así se requiere– tomar las mejores prácticas documentadas y agregarles principios de lógica, abstracción y métodos formales para estructurar un modelo semiformal para documentar la elicitación. Los que se proponen actualmente se centran en las técnicas de recogida de información y prestan poca atención a la documentación. Además, estos modelos se basan principalmente en el lenguaje natural, por lo cual es difícil su interpretación, y generan reprocesos para las etapas posteriores del ciclo de vida debido a las ambigüedades. Conclusiones: En este artículo se describe un modelo estructurado, así como su aplicación y validación mediante la comparación con cinco modelos encontrados en la revisión