An Active Hypertext Model for System Requirements 1 . Introduction 2 . Conversational Model

We are developing tools to support a conversational metaphor for requirements definition and analysis. Our conversational model consists of three components: (1) a hypertextual representation of requirements and their interrelations, (2) an issue-based speech act model, and (3) a typology of changes. These components act together in a model we call the Inquiry Cycle. We discuss requirements analysis activities supported by the conversational model, including information retrieval and navigation, rationale management, and agenda management. We have implemented a prototype active hypertext system, and we have applied our model and implementation to the requirements for an ATM banking system, an example we use in the paper for illustration. We are developing tools to support a conversational metaphor for requirements definition and analysis. We view requirements definition as an extended dialogue between stakeholders who are planning the capabilities of a new system. Our emphasis lies firmly in inquiry and questioning during the production process, not the linguistic details of the product or the transformational properties of the production process. We pay particular emphasis to where information needs to come from and when. We have developed a conversational framework, the inquiry cycle, that underpins our technology development. To support the inquiry cycle, we have developed the concept of active hypertext. Our hypertexts consist of interconnected fragments of semi-structured information (usually text) about the requirements. They are active in three senses: (1) they capture the process by which the requirements become elaborated and agreed upon, and not just a snapshot of the current or final state of the requirements, (2) they directly support the ongoing process of inquiry and scrutiny so that users of the hypertext know what information needs to be sought and what decisions or assumptions are pending, and (3) they support information consolidation, so that information of only transitory interest can be simplified and summarized once a decision has been made. The conversational metaphor, the inquiry cycle and active hypertext technology are our responses to the difficulties faced in requirements definition situations for real computer-based systems. Lubars, Potts and Richter (1993a) in their field study of requirements practices in 23 project organizations discovered that the principal problems faced by project teams were communication, agreement and change. The elaboration of requirements is an inquiry-driven iterative process. Particularly in the case of market-driven projects, definition and analysis, expression and validation, requirements and design are tightly interwoven. The next section describes our conversational model. It consists of three components: (1) a hypertextual representation of requirements and their interrelations, (2) a speech act model, and (3) a typology of changes. These components act together in a model we name the Inquiry Cycle. Section 3 discusses requirements analysis activities that must be supported by the conversational model. These include information retrieval and navigation, rationale management, and agenda management. Requirements validation, and the specific analyses that help in validation, are regarded as special forms of information retrieval. Throughout, we illustrate our points by referring to the requirements for an ATM banking system. Section 4 describes the current status of our work, particularly the prototype active hypertext system. Section 5 discusses related and previous work, and Section 6 contains our plans for future work. A conversation consists of four things: participants, shared information, speech acts, and effects. In the case of system requirements, the participants are ‘stakeholders’, those with a stake in the outcome. We leave this term deliberately vague in preference to defining conversational roles such as ‘customer’, ‘requirements analyst’, ‘end user’, etc. Although the prototype active hypertext system to be described later lends itself to use primarily by analysts working in customer-specific projects with an originating requirements document to start from, other implementations of the conversational metaphor could equally support participatory design. The remaining three components and their interrelationships are depicted in Figure 1. In the next An Active Hypertext Model for System Requirements