![]() Every use case must involve a system-external actor, otherwise you're not describing the system from the outside.Ī better set of actors for a forum system would probably be Poster, Reader and Manager (and possibly a System Administrator as well). Use case diagrams are simply another diagram type which represents a users interaction with the system. ![]() In other words, if you find yourself using actors which are in fact concepts from within the system, you've taken a wrong turn somewhere. Why? Because the interaction is actually between the system and a person, whereas a user (account) is an in-system representation of a person's privileges. There is of course no right or wrong, but generally speaking it's a bad idea to use actors such as "logged in user" etc, and in fact you should avoid employing a "user" actor at all. In Microsoft Visio 2007, you can find UML Model Diagram by following like this: Click File > New > Software and Database > UML Model Diagram (Metric) / UML. Visio is a diagramming app that you can use to create flow charts, network diagrams. Create data-driven Visio diagrams in Microsoft Excel. Elaboration is typically done using an activity diagram which describes how the interaction between the actor and the system proceeds, eg Poster initiates post System checks poster's privileges System rejects post if privileges are insufficient etc. In this step-by-step tutorial, learn how to get and use Microsoft Visio. The next step is to elaborate your use cases, and that's where you can start talking about conditions. The number of use cases does not translate directly into system complexity, and a large number of clearly defined use cases is better than a small number of large, ambiguous ones. You should not be overly concerned with the number of use cases at this stage. To a person using a forum, it does make sense that creating a post is a separate activity from updating one (or responding to one), so that seems like a sensible start to me. You want to keep that description simple and succinct.Įach use case should in some way make sense to the actor. A set of use cases is intended to provide an overview of the system's functionality, and each use case describes an interaction between the system and one or more actors. You shouldn't get into conditions and ifs and buts in use cases diagrams.
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