Raj, here is what you need to do to transform Business requirements into functional requirements. Also Make use case for each function of system
a) Create project-initiation diagrams flow that includes business use case activity diagram workflow, diagrams flow charts, etc.
b) Determine project scope and derive context diagrams and project use cases from the business diagrams
c) Detail the use cases by using activity diagrams or other techniques
d) Create high level analysis dataflow diagrams, domain class diagrams, and entity-relationship diagrams from the use cases or other high level diagrams
e) Recognize and understand the various design models including the other relevant types of UML diagrams detailed design entity-relationship diagrams and decomposed dataflow diagrams
f) Determine when to use which modeling technique following them through a project life cycle and understand which diagrams are derived from others
g) Understand the basic concepts of normalization and decomposition so can converse intelligently on the topic and review diagrams that have been normalized or decomposed.
I hope this helps.........
Manoj