High level use cases are nothing but which include lot of functionality and its even complex to implement.Based on the functionality we write the use cases. For any use case BA need to maintain Use Case document which depict main scenarios, attributes, actors of a usecase. Use case document is nothing but a list of use cases and adjacent to each and every use case a BA should have a use case daigram so that if any one look into the daigram they should get to know what the use case is about.This is maily for SMEs(Subject Matter Experts) so called Users who dont have much time to go thru the whole use case.
A high level use case tends to be more narrative.It would be description in a paragraph or two depicting the high level requirements relative to the application
