2.4 System requirements modelling using case study Requirement modelling is an important activity in the process of designing and managing enterprise architectures. Requirements modelling helps to understand, structure and analyse the way business requirements are related to Information Technology requirements, and vice versa, thereby facilitating the business-IT alignment. It includes actors, use cases and use case scenario. Each of these is further describe in following subsection:
Actors: An actor is a user or external system with which a system being modelled interacts. For example, in our inventory management system involves various types of users, including supplier, inventory management system, human resources, and manufacturer. These all users are actors. At the same time, an actor is external to a system that interacts with the system. An actor may be a human user or another system, and has some goals and responsibilities to satisfy in interacting with the system.
It is also necessary to generate actor who giving compact overview of the whole model. We have to prepare requirement specification model that incorporates the package details diagram, showing package use cases, their associations with actors and relationships between use cases including uses cases. For making good requirement modelling system engineer prepares activity diagrams visualizing scenarios of complex use cases. In model, the activities should be nested within appropriate use cases and assigned as their behaviours. And finally we describe use cases according to pre-defined templates, e.g. rational unified process use case document, actors in Figure 5.