Typically identifies problems with requirements defnition and uncover gaps between business stakeholder expectations and the actual deliverables being produced.

UAT and Business Driven Testing can be executed in parallel.Specifically UAT is constructive test of the software from the business perspective.In other words ,the users are asking "Will this system work in our daily business environment?". All areas of the business that will use the system should be representated during Success crieteria for UAT will be defined in the Test Strategy document .The business case owner who will verify that application was tested by complete representation of knowledgeable business users during UAT signoff.

User Review and UAT execute the same test cases at different times .User Review will take place as soon as the system is stable in the System Test Environment.User Review checks at a high level that the software addressed meets the business need .In some cases a two phased UAT may not be necessary ,but is usually beneficial because there is more time for remediation after User Review.