Modeling and Tracing Stakeholders' Goals across Notations using RE-Tools

Abstract

The ability to represent stakeholders' goals and their operationalizations, through tasks, resources, system requirements and specifications, helps better ensure that the projected system meets its intended goals. To offer such an ability, various notations have been developed, but somewhat independently of each other, each for its own concepts and with its own tool. As a result, it is difficult to establish end-to-end traceability among the various concepts. This paper presents RE-Tools - a toolkit towards an integrated modeling of such concepts, using i *, the NFR framework, KAOS and Problem Frames. RE-Tools uses a meta-model approach to representing and integrating the notations, which includes shared, generalized meta-classes and cross-notational goal achievement contribution links. This approach is intended to allow for a uniform application of the Label Propagation Procedure in determining goal achievement across the supported notations, using either the open or closed world assumption.

Status Industry use

RE-Tools[1] 2.0

http://www.utdallas.edu/~supakkul/tools/RE-Tools i * [ 2 ], NFR Framework [ 3 ], KAOS [ 4 ], Problem Frames [ 5 ], UML Modeling and reasoning support, foundation for other tools [ 6 ] Integrated modeling environment, automated and integrated Label Propagation Procedure using open or closed world assumption, UML Profile-based meta-model, navigatable inmemory models, interchangeable XMI/XML file format, extension via plug-in and APIs, open-source, Windows OS supported.

Publicly available since 2009, with around 1,300 downloads from around 65 countries to date, for use in teaching, research, and industrial practice, including Australia, Brazil, Canada, China, France, Italy, the Philippines, Spain, UK, and the US Internal use at Sabre and Pentathlon Systems Resources 2

Integrated Modeling and Tracing Goal Achievement RE-Tools previously supported independent modeling of the supported notations and limited integration [ 1 ]. The tool has recently been enhanced to support a more comprehensive integration across multiple notations. Fig. 1 illustrates the key features of the enhancements, with the corresponding meta-classes shown in blue. Suppose the Record ambulance location Requirement in Problem Frames is determined to be satisficed (denoted by a check mark) by the system. Using the Label Propagation Procedure [ 7 ], the satisficing is propagated across the Make(++) contribution to derive that the Ambulance location recorded Goal in KAOS is also satisficed. The propagation is then repeatedly applied across the next contribution links in a cascading fashion upward the graph until the propagation cannot proceed any further because the needed information along the various paths is not available (e.g., the achievement of some sub-goals of an AND decomposition is undefined) or it has reached and evaluated the top-level Agents’ goals (e.g., Timeliness[Ambulance arrived at scene] Softgoal).

To support the integrated modeling and reasoning, achievement contributions are represented as links between a parent Proposition and its offspring Proposition(s). Proposition is captured as a generalized meta-class in the meta-model, which is shared by the concepts in the supported notations (e.g., Hardgoal, Softgoal, BehavioralGoal, Task, Resource, Requirement). By applying the Label Propagation Procedure at the shared generalized Proposition meta-class level, RE-Tools performs reasoning about goal achievement generically and uniformly across the different notations. 3

Discussion and Future Work The notion of (hard) goal achievement in i * and KAOS are generally treated in an absolute sense (satis ed or (absolutely) denied ), while the notion of Softgoal achievement in the NFR Framework is “good enough”, reflecting the more subjective, interacting, relative nature (satis ced, weakly satis ced, denied, weakly denied ). To support a more general and uniform label propagation, RE-Tools adopts and applies the weaker notion (satisficing) with an assumption that satis ced and (soft) denied could at least roughly be translated to the notions of satis ed and (absolutely) denied in some cases. However, additional research is required to better understand this approach, compare it with other integration approaches, as well as understand how to use multiple notations together.

Additionally, RE-Tools currently requires human intervention to trigger the automatic cascading label propagation process by first manually labelling the goal achievement of leaf-level nodes, which could be inaccurate or time-consuming. We are investigating ways to help alleviate these problems in some situations by integrating RE-Tools with other development notations and tools (e.g., BMPN [ 8 ] and URN [ 9 ]), and simulation tools [ 10 ] to automatically obtain the actual or simulated goal achievement of the leaf-level nodes. Furthermore, from the requirements modeling perspective, the tool may need to be extended to support other ontological concepts, such as quality constraints and domain assumptions.

References

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