Stakeholder Requirements Use Scenario Use scenario One basic

Stakeholder Requirements Use Scenario

Use scenario • One basic structuring mechanism for discussing capability requirements is the operational or use scenario. • Scenarios provide an excellent method for exploring requirements with stakeholders • Stakeholder requirements use the notion of a scenario as a means of establishing a framework in which meaningful dialogue can take place.

Use Scenario • The scenario encourages the stakeholders to think about the job that they are doing and how they would like to do it. • Once the scenario has been agreed, individual requirements can be generated to define precisely what the stakeholders would like to be able to do at each point in the scenario • The purpose of creating a scenario is to promote understanding and communication. • A scenario is not itself a requirement; it is rather a structure for elicitation of requirements.

Use Scenario • A scenario is the sequence of results produced (or states achieved) through time for the stakeholders. • a use scenario may be represented as a hierarchy of goals and represents the capabilities provided by the system to the stakeholder – without saying how to provide them.

• Scenario is seen to be beneficial for the following reasons: - enables stakeholders to step through operational use; - missing steps can be found; - different stakeholders can have different scenarios; - time constructs can be identified

• The basic question to ask the stakeholder is: – ‘What do you want to achieve’? – ‘What state do you want to be in’? • If the system is completely new stakeholders need to use their imagination and postulate what they want to happen or achieve at each step.

Goal Hierarchy • Procedure:

Example

• The example covers all the aspects of the trip starting with loading the boat on to the car, getting ready to sail, sailing and returning home. • The scenario: - follows a time sequence; - its nodes are high-level capabilities; - shows alternatives; - shows periodic repeated behavior; - shows where sequence is not important (parallel branches); - shows exceptions.

• missing capabilities: - able to transport the loaded boat - able to launch boat

Constraints • A constraint is a type of requirement that does not add any capability to a system. • Instead, it controls the way in which one or more capabilities are to be delivered. • For example, consider the following: 'A customer shall be served within 15 minutes of placing the order'.