BRD Describes the business information of the client.once we are clear abt BRD of the client then only we can create more acurate solutions.this is the initial document that helps to create Business models in Cognos and ReportNet.Actually this information we are getting by KT(Knowledge Transfer) session.

Usecase Document helps to create test case document during unit testing ,actually use case document contains testcase id and i/p values that should use during testing , we are using this id only in Test case document instead of specifying all these i/p values and some other ,that id itself describing all that.so we can say use case is the foundation document for test case document.