Formal refinement patterns for goal-driven requirements elaboration

Abstract

Requirements engineering is concerned with the identification of high-level goals to be achieved by the system envisioned, the refinement of such goals, the operationalization of goals into services and constraints, and the assignment of responsibilities for the resulting requirements to agents such as humans, devices and programs. Goal refinement and operationalization is a complex process which is not well supported by current requirements engineering technology. Ideally some form of formal support should be provided, but formal methods are difficult and costly to apply at this stage.This paper presents an approach to goal refinement and operationalization which is aimed at providing constructive formal support while hiding the underlying mathematics. The principle is to reuse generic refinement patterns from a library structured according to strengthening/weakening relationships among patterns. The patterns are once for all proved correct and complete. They can be used for guiding the refinement process or for pointing out missing elements in a refinement. The cost inherent to the use of a formal method is thus reduced significantly. Tactics are proposed to the requirements engineer for grounding pattern selection on semantic criteria.The approach is discussed in the context of the multi-paradigm language used in the KAOS method; this language has an external semantic net layer for capturing goals, constraints, agents, objects and actions together with their links, and an inner formal assertion layer that includes a real-time temporal logic for the specification of goals and constraints. Some frequent refinement patterns are high-lighted and illustrated through a variety of examples.The general principle is somewhat similar in spirit to the increasingly popular idea of design patterns, although it is grounded on a formal framework here.

A Three-Dimensional Abstraction Framework to Compare Multi-Agent System Models

“…clusterbased internal [11] (crime); [20] (organisation); [38], [45] (joint goals and intentions); [2], [37], [43] (epidemics) behavioural [34], [29], [41], [35], [28], [9] (organisation); [49], [57], [62] (ecological) temporally global agentbased internal [47], [24], [25], [64], [63], [48] (requirements); [31], [50], [59], [4], [21], [6], [7], [10], [12], [40] (verification) behavioural clusterbased internal [24], [25], [34], [29], [30], [41], [36], [18], [55], [64], [65] (requirements, enterprise); [43], [2], [37] (epidemics); [49], [57], …”

Compositional Verification of a Multi-Agent System for One-to-Many Negotiation

“…For example, linear or branching time temporal logic are appropriate to specify various agent (system) behavioural properties. Examples of formal requirement specification languages based on such variants of temporal logic are described in [9], [10], [14], [22]. However, for adaptive agents, it might be necessary to specify adaptive properties such as 'exercise improves skill' for which we have to explicitly express a comparison between different histories.…”

Requirements-Level Semantics and Model Checking of Object-Oriented Statecharts

“…If the composition of the system with its environment is intended to achieve emergent properties E, then the requirements engineer should look for assumptions A about the environment and properties S of the system such that A and S jointly entail E. This approach puts NYAM in the same class of requirements methods as KAOS [15,16], the requirements reference approach of the Gunters, Jackson and Zave [17,18] and, to some extent, SCR [19][20][21]. We call the argument that the environment and the system jointly assure the emergent properties the systems engineering argument.…”

“…Dwyer et al [60] have found a list of eight patterns in temporal properties and in the KAOS project [15,45] goal-oriented refinement patterns have been identified. We intend to look at the problem frames identified by Jackson [18] to see if we can build a library of formally verified patterns, plus guidelines to recognise and use these patterns.…”