Description of Wireless Intelligent Network Services with Use Case Maps Daniel Amyot and Rossana Andrade 1 TSERG, School of Information Technology and Engineering, University of Ottawa 150 Louis Pasteur, Ottawa, Ontario, K1N 6N5, Canada E-mail: {damyot | randrade}@site.uottawa.ca Abstract. Increasing complexity in telecommunications services requires ever more complex standards, and therefore the need for better means to write them. Over the years, scenario-driven approaches have been introduced in order to describe functional aspects of systems at several levels of abstraction. Their application to early stages of design and standardization processes raises new hopes in editing concise, descriptive, maintainable, and consistent documents that need to be understood by a variety of readers. In this context, this paper investigates a recent visual notation for causal scenarios called Use Case Maps. The goal is to better describe distributed systems and telecommunication standards, and to fill the gap between the stage where services are described informally and the stage where message sequence information is generated. As an example, this paper focuses on the Incoming Call Screening service of the new Wireless Intelligent Network standard. Keywords. Causal Scenarios, Message Sequence Charts, Telecommunication Standards, Use Case Maps, Wireless Intelligent Network. 1. INTRODUCTION Emerging telecommunications services require industries and standardization bodies (ANSI, ETSI, ISO, ITU, TIA, etc.) to describe increasingly complex functionalities, architectures, and protocols. This is especially true of wireless systems, where the mobility of users and of terminals brings an additional dimension of complexity. In that context, special attention has to be brought to the early stages of the design and standardization processes, where the focus should be on system and functional views rather than on details belonging to a lower level of abstraction, or to later stages in those processes. Nowadays, communication services and features are commonly described using an amalgam of informal operational and declarative descriptions, tables, and visual notations such as Message Sequence Charts (MSCs) [15]. As these descriptions evolve, they quickly become error-prone and difficult to manage. There is an urgent need for high-quality documents that are concise, descriptive, maintainable, consistent, and understandable by readers with different needs and perspectives (designers, engineers, testers, marketing people, etc.). Over the years, several approaches have attempted to provide such documents. Proponents of formal methods have claimed to solve the problem by providing unambiguous and mathematical notations and verification techniques, but the penetration of these methods in industry and in standardization bodies remains, unfortunately, low [3]. Scenario-driven approaches have raised a higher level of interest and acceptance, mostly because of their intuitive representation of services [3][16]. This paper presents such a methodology, but with an approach to the level of scenario abstraction slightly different from that of most popular techniques. It focuses on the very first stage of design and standardization processes, where many information and design decisions are often lost or hidden behind implementation details. Such details should be omitted at this stage, whereas the general flow of responsibilities should be emphasized. 1 Professor at the Computer Science Department, Federal University of Ceará, Brazil, and sponsored by CAPES (Brazilian Federal Agency of Graduate Studies).