Hi kumarrohit,
The use cases describe typical interactions between the users of the system and the system itself. They provide a narrative of how the system is used and each use case focuses on a common user goal. Examples from the famous ATM use case are: "get cash", "get balance".
The functional requirements describe the system's functionality like:
· The system should grant access to the user after he provides username and password;
· The system should provide access to the following pre-defined reports…. Followed by the list of reports;
· Etc.
Often they are listed under different project specific groups like user access, reporting, user interface, etc.
When you look at the above examples for use cases and functional requirements it is easy to see that the use case of "get balance" corresponds to the functionality "The system should provide access to pre-defined reports… “These are the similarities.
The difference is in the way the information is presented. The use cases describe what should happen for example when the user enters the wrong username and password, while the functional requirement may only state that the “system should grant access to the user after he provides username and password.” In addition, the use cases are backed up by activity, sequence, state, etc. UML diagrams. This use case model might be also published on the intranet, via the tool used to create the diagrams, and might be further linked to the logical and physical database models.
There could be variations depending on the standards established at the place you work, the specific project at hand, and the familiarity of the project team with use cases and UML.
Let me know if this helps,
Vessela