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| Are use cases the functional requirements or do you think functional requirements are different from use cases? |
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Question: Are use cases the functional requirements or do you think functional requirements are different from use cases?
Statistics: (5842 Views)
(2 Additional Answers/Comments)
Posted by: sekharny on Thursday, May 01, 2008
Categories: Use Cases, Requirements Analysis (BABOK KA), Elicitation (BABOK KA), Requirements Management and Communication (BABOK KA)
Answer:
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It is generally accepted that use cases, specified in narrative form (also known as use case specifications), depict functional requirements. This is because a use case, via the main and alternate flows, shows how a user interacts with a system in order to achieve a desired result.
That's exactly the purpose of a "functional requirement" to describe the functions and behaviors that a system is or should be capable of.
Therefore, if use cases are used and narrated in detail for a project, there is no need for separate documentation to describe the functional requirements because the totality of all the use cases represent the set of functional requirements for a given system/project. |
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| Additional Answers/Comments |
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Posted by
ksimaan on
Tuesday, May 06, 2008 11:39 PM
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Use cases serve their purpose well when their syntax describes the “required” functionality from the system in response to the user interaction, without getting into the details of “how” to execute this functionality. In other words, the system is a black box from the use case perspective.
Using the above style, every use case line that states “system does …< something>”, is a function that the system is expected to perform and therefore can be a potential Functional Specification.
In the famous ATM example, the use case considers the system that operates the ATM machine as a black box. A typical scenario would be:
1- User inserts the ATM card
2- System validates the inserted card is valid to execute financial transactions on this ATM machine
3- System prompts the user to enter PIN number
4- User enters PIN number
5- System validates the PIN number
..
..
In the above example, steps 2, 3 and 5 represents a functionality that the use case author is requesting the system to perform. Or, in the “formal” functional specifications syntax, steps 2, 3 and 5 are translated to:
The system shall validate the inserted card is valid for financial transactions on this ATM machine
The System shall prompt the user to enter PIN number
The System shall validate the PIN number entered by the user
However, there may be cases where a use case line will not qualify to be a Functional Specification, although it starts with “System does something…”.
Can you come up with any examples?
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Posted by
MostafaElbarbary on
Sunday, May 25, 2008 10:12 AM
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n his book (Aspects oriented software development) Ivar Jabcoson has distinguish between two major categories of use cases: application and infrastructure use cases. Application use cases describe how users interact with the system to perform the desired functionality(to capture functional requirments). Infrastructure use cases describe what the system does to add qualities such as usability, reliability, performance, and supportability to each step of an application use case(non fncational requirements).
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