Difference between revisions of "Preliminary Use Cases"
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Revision as of 07:45, 15 May 2009
What
Preliminary Use Cases - Short and simple diagrams that describe the user's interaction with the system in different situations.
How
The Dish
Preliminary Use Cases. Ingredients
Process
Read and understand the stories from the storycards or the story from the storytelling.
Draw diagrams that visualise the stories focused on the user's requests and the system's answers to his requests.
Do not focus on exception handling and functions which would be considered as details in the system. Keep focus on the main functions which the system was actually meant to handle; things like: "Insert money to account", but not things like: "What happens if the power disappears during a money transfer?"
Use arrows to connect the user's requests and the system's answers, so that it is possible to see a flow through the dialogue. Thereby it becomes easier to read and understand for the non-technical customer.
When the diagrams have been drawn, consult the customer and ask him if he can recognise the pattern in the diagram, and if the system's answers to the user's request are as he had expected. If the user has to many changes to the diagrams, then it could be necessary to redraw it and consult the customer again.
Why
The main goal of the preliminary use cases is to present the stories from storytelling and/or the storycards in a slightly more technical way. The purpose is to let the developer use them as a link between the non-technical stories and the more technical class diagrams and state machine diagrams. It can be difficult to draw a sequence diagram or other more technical tasks, depending only on the stories. The preliminary use cases give the developer an overview of the complexity of the system-to-be.
It is important to remember that it is not expensive to make changes at this early stage of the project, therefore you should consult the customer and explain the various diagrams, so that he/she can reflect upon them.
Example
This is a simple example of how to use preliminary use cases to describe the communication between a heating system and a user. The communication medium is a web browser.
