Towards Modelling and Reasoning Support for Early-Phase Requirements Engineering درس مهندسی نیازمندی ها استاد دکتر عبداله زاده دانشجو خیرالنسا مرچانت

Introduction  Increasing attention in RE  Early stages of the system development life cycle are crucial to the successful development and subsequent deployment and ongoing evolution of the system  computer systems play increasingly important roles in organizations  there is a need to pay more attention to the early stages of requirements engineering itself

Stating the problem  Much of requirements engineering research has taken as starting point the initial requirements statements, which express customer ’ s wishes about what the system should do ambiguous incomplete inconsistent informal

Importance of RE  System development involves a great many assumptions about the embedding environment and task domain  Users need help in coming up with initial requirements in the first place  Systems personnel are increasingly expected to contribute to business process redesign

Importance of RE (Cont.)  Having well-organized bodies of organizational and strategic knowledge would allow such knowledge to be shared  As more and more systems in organizations interconnect and interoperate, it is increasingly important to understand how systems cooperate  Dealing with change is one of the major problems

The i* modelling framework  The i* framework was developed for modelling and reasoning about organizational environments and their information systems The Strategic Dependency (SD) model The Strategic Rationale (SR) model  The central concept in i* is that of the intentional actor

Strategic Dependency model  Consider a computer-based meeting scheduler for supporting the setting up of meetings

Defects of requirements models  Why is it necessary to schedule meetings ahead of time?  Why does the meeting initiator need to ask participants for exclusion dates and preferred dates?  Why is a computer-based meeting scheduler desired? And whose interests does it serve?  Is confirmation via the computer-based scheduler sufficient? If not, why not?  Are important participants treated differently? If so, why?  They tend to focus on the “ what ” rather than the “ why ”

Strategic Dependency model for meeting scheduling, without computer based scheduler

Strategic Dependency model for meeting scheduling with computer-based scheduler

Modelling stakeholder interests  The Strategic Dependency model provides one level of abstraction for describing organizational environments and their embedded information systems Showing External relationships among actors Hiding the intentional constructs within each actor

Modelling stakeholder interests (Cont.)  In the framework, the Strategic Rationale model provides a more detailed level of modelling by looking “ inside ” actors to model internal intentional relationships

Strategic Rationale model for meeting scheduling

Strategic Rationale model for a computer-supported meeting

The modelling and reasoning support needs of early-phase RE  Knowledge representation and reasoning  Degree of formality  Incorporating intentionality  Multi-lateral intentional relationships

The modelling and reasoning support needs of early-phase RE (Cont.)  Distributed intentionality  Means-ends reasoning  Organizational actors

Conclusions  Understanding “ why ” has been considered an important part of requirements engineering since its early days  Frameworks and techniques to explicitly support the modelling of and reasoning about agents ’ goals and rationales have recently been developed in RE  making a distinction between early-phase and late-phase RE could help clarify the ways in which concepts and techniques could be applied to different RE activities

Reference  Eric S. K. Yu, "Towards Modeling and Reasoning Support for Early-Phase Requirements Engineering," re, p. 226, Third IEEE International Symposium on Requirements Engineering (RE'97), 1997