We propose a new domain model for representing software functional requirements that can help the subsequent phases of design, development, and testing. The model consists of a use-relationship between the operations and the data-items and a finite-state model for the valid sequences of those operations. We show how this model can help us in the analysis and structuring of the requirements via the identification of submodels, which in turn can simplify the design and other phases. We also give an algorithm to compute the use-relationship for an objectoriented source-code as a reengineering step for requirements verification. We give several detailed examples.