Reconciling Use Cases and Operational Profiles

Greg Butler
Adrian Cretu
Ferhat Khendek
ABSTRACT
Location Register(VLR), which is the local database of
information on subscribers utilizing this cell or region. Our trial incorporated information for operational proles into a few use cases that had been developed for the VLR logical node.
SWITCH BASE STATION
Keywords
VLR
SWITCH
1 INTRODUCTION
MOBILE STAtext for Mobile Telephony Example We will have two running examples: (Ex1) is a highlevel simpli ed view of telephony that is intended to be understood by the general reader and to avoid the technical details within the switch; and (Ex2) is the VLR case study, where the distinction between requirement functions and implemented operations is not so clear cut, because the VLR node is quite close to the hardware. It should be kept in mind that all our probabilities given in pro les are purely ctitious. We present the background material on use cases and operational pro les together with the description of a simple formal model of event sequences that underlies both use cases and operational pro les. Section 5 presents a combined view of the concepts from both use cases and operational pro les. In the conclusion we highlight the bene ts of the combined approach. There are many de nitions of use cases and its associated terminology. Most of our work was settling on the appropriate set of de nitions in order to make the reconciliation with operational pro les comprehensive. In contrast, the terminology for operational pro les is well-de ned in the literature.
2 USE CASES
This section provides background on use cases and de nitions of the terminology. It is divided into a discussion
of context in terms of the host system, de nitions of use cases and scenarios, then a presentation of the many ways to describe scenarios, and a discussion of methodology. We end with a discussion of how use cases are applied throughout the software life-cycle. There are many viewpoints of use cases in the literature. Our viewpoint is drawn mainly from Cockburn 4] and Regnell 14].
Host System
Figure 3: Two (Host,Target) Contexts
sibility that must be ful lled 4, 8].
Reconciling Use Cases and Operational Pro les
Dept of Computer Science Dept of Elec. & Computer Eng. Dept of Elec. & Computer Eng. Concordia University Concordia University Concordia University Montreal H3G 1M8 Canada Montreal H3G 1M8 Canada Montreal H3G 1M8 Canada Tel: +1-514-848-3000 Tel: +1-514-848-3100 gregb@cs.concordia.ca khendek@ece.concordia.ca
A reconciliation of use cases and operational pro les is presented as a means for requirements engineering, prioritizing development and testing, and allowing statistical use testing and reliability estimation. We have trialed the combined application of use cases and operational pro les in an industrial setting. use case, operational pro le, requirements engineering, reliability Use cases capture the functionality of a system. They have been shown to improve requirements gathering as they are accessible to users. Use cases have also been used as the basis of project management, and for traceability across development and test phases. Operational pro les capture quantitative usage information of a system. They allow statistical use testing and reliability estimation, as well as prioritization of tasks during the software process. A reconciliation of uses cases and operational pro les is presented as a means for requirements engineering, prioritizing development and testing, and allowing statistical use testing and reliability estimation. The reconciliation shows how the use case model for a system can include an operational pro le, thus capturing both functional speci cation and a quantitative usage specication. We have trialed the combined application of use cases and operational pro les in an industrial setting 6] from mobile telephony. Figure 1 gives the overall context showing the Home Location Register(HLR), which is a database of subscriber information, and the Visitor
Mobile Telephony System
Switching System
Subscriber Callee
Operator
Switch VLR-2
HLR
Switching System
VLR
Host System Environment
Use cases capture the functionality of a system, called the target system, as it is meant to behave in a given environment called the host system. A use case describes how a group of external entities, called actors, make use of the system under consideration. The use they make is modeled by the passing of signals or information between the actors and the system. We will call these messages. Sometimes it is useful to distinguish between stimuli, which are messages from actors to the system, and responses, which are messages from the system to actors. Figure 2 illustrates one view of the host system, where the target system is just one of the actors. All actors interact, as shown by the arrows, but use cases model only the interactions with the target system (the solid arrows). Many descriptions of the target system's requirements do not model the other interactions, although they are important 7, 18].