Peter Haumer

A proposal for a scenario classification framework

The requirements engineering, information systems and software engineering communities recently advocated scenario-based approaches which emphasise the user/system interaction perspective in developing computer systems. Use of examples, scenes, narrative descriptions of contexts, mock-ups and prototypes-all these ideas can be called scenario-based approaches, although exact definitions are not easy beyond stating that these approaches emphasise some description of the real world. Experience seems to tell us that people react to ‘real things’ and that this helps in clarifying requirements. Indeed, the widespread acceptance of prototyping in system development points to the effectiveness of scenario-based approaches. However, we have little understanding about how scenarios should be constructed, little hard evidence about their effectiveness and even less idea about why they work.The paper is an attempt to explore some of the issues underlying scenario-based approaches in requirements engineering and to propose a framework for their classification. The framework is a four-dimensional framework which advocates that a scenario-based approach can be well defined by itsform, content, purpose andlife cycle. Every dimension is itself multifaceted and a metric is associated with each facet. Motivations for developing the framework are threefold: (a) to help in understanding and clarifying existing scenario-based approaches; (b) to situate the industrial practice of scenarios; and (c) to assist researchers develop more innovative scenario-based approaches.

Requirements elicitation and validation with real world scenes

A requirements specification defines the requirements for the future system at a conceptual level (i.e., class or type level). In contrast, a scenario represents a concrete example of current or future system usage. In early RE phases, scenarios are used to support the definition of high level requirements (goals) to be achieved by the new system. In many cases, those goals can to a large degree be elicited by observing, documenting and analyzing scenarios about current system usage. To support the elicitation and validation of the goals achieved by the existing system and to illustrate problems of the old system, we propose to capture current system usage using rich media (e.g., video, speech, pictures, etc.) and to interrelate those observations with the goal definitions. Thus, we aim at making the abstraction process which leads to the definition of the conceptual models more transparent and traceable. We relate the parts of the observations which have caused the definition of a goal or against which a goal was validated with the corresponding goal. These interrelations provide the basis for: 1) explaining and illustrating a goal model to, e.g., untrained stakeholders and/or new team members; 2) detecting, analyzing, and resolving a different interpretation of the observations; 3) comparing different observations using computed goal annotations; and 4) refining or detailing a goal model during later process phases. Using the PRIME implementation framework, we have implemented the PRIME-CREWS environment, which supports the interrelation of conceptual models and captured system usage observations. We report on our experiences with PRIME-CREWS gained in an experimental case study.

Scenario usage in system development: a report on current practice

Summary form only given. Scenario-based approaches are attracting more and more interest in requirements engineering research and practice. The research literature offers an increasing number of scenario-related methods, models and notations which highlight the consideration of concrete system descriptions from a usage-oriented perspective, prior to abstract conceptual modelling of function, data and behavior. Scenario use is also becoming a pervasive phenomenon in industrial practice, but comprehensive and expressive studies on the practical relevance of the techniques proposed by research are still rare. The European ESPRIT project CREWS (Cooperative Requirements Engineering With Scenarios) aims at a deeper understanding of the diversity of scenarios, in order to help improve methodological and tool support for scenario-based requirements engineering. The authors consider the two-pronged strategy being followed to gain this understanding.

PRIME—toward process-integrated modeling environments: 1

Research in process-centered environments (PCEs) has focused on project management support and has neglected method guidance for the engineers performing the (software) engineering process. It has been dominated by the search for suitable process-modeling languages and enactment mechanisms. The consequences of process orientation on the computer-based engineering environments, i.e., the interactive tools used during process performance, have been studied much less. In this article, we present the PRIME (Process Integrated Modeling Environments) framework which empowers method guidance through process-integrated tools. In contrast to the tools of PCEs, the process-integrated tools of PRIME adjust their behavior according to the current process situation and the method definitions. Process integration of PRIME tools is achieved through (1) the definition of tool models; (2) the integration of the tool models and the method definitions; (3) the interpretation of the integrated environment model by the tools, the process-aware control integration mechanism, and the enactment mechanism; and (4) the synchronization of the tools and the enactment mechanism based on a comprehensive interaction protocol. We sketch the implementation of PRIME as a reusable implementation framework which facilitates the realization of process-integrated tools as well as the process integration of external tools. We define a six-step procedure for building a PRIME-based process-integrated environment (PIE) and illustrate how PRIME facilitates change integration on an easy-to-adapt modeling level.

Bridging the gap between past and future in RE: a scenario-based approach

Requirements engineering (RE) investigates the impact of a future-oriented change vision, but the move towards this vision must consider a context heavily shaped by the past. As RE becomes a continuous process throughout the system lifecycle, it must achieve an effective combination of envisionment and traceability. We describe a scenario-based solution to this problem which is based on an integration of five ingredients: the persistent capture of context in the form of real world scenes captured in multimedia; formal agent-oriented modelling with a semantics that allows distributed interactive animation; message trace diagrams as a medium for exchanging animation test cases and traces; a goal model to control and record the RE process; and a process-integrated tool environment to ensure method-guidance and traceability with as little effort as possible. In addition to the basics of our approach, we also describe its prototypical implementation in the CREWS-EVE environment and demonstrate its usefulness with examples from a case study in the production industry.

Improving reviews of conceptual models by extended traceability to captured system usage

Abstract When specifying change for an existing system, the history and functionality of the system to be replaced has to be considered. This avoids neglecting important system functionality and repeating errors. The properties and the rationale behind the existing system can be elicited by analysing concrete system-usage scenarios [Pohl, K., Weidenhaupt, K., Domges, R., Haumer, P., Jarke, M., Klamma, R., 1999. Process-integrated (modelling) environments (PRIME): foundation and implementation framework. ACM Transactions on Software Engineering and Methodology (TOSEM), vol. 8, no. 4, pp. 343–410]. The results of the analysis of the existing system are then typically represented using conceptual models. To establish conceptual models of high quality reviewing the models is common practice. The problem faced with when reviewing conceptual models, is that the reviewer cannot assess and therefore understand the basis (concrete system usage) on which the conceptual models were built. In this paper, we present an approach to overcome this problem. We establish Extended Traceability, by recording concrete system-usage scenarios using rich media (e.g. video, speech, graphic) and interrelating the recorded observations with the conceptual models. We discuss the main improvements for review processes and illustrate the advantages with excerpts from a case study performed in a mechanical engineering company.