This research studies the effects of 1) association changes in database semantics, 2) file composition and decomposition, and 3) the conversion of one DBMS to another to the application programs. A methodology of application program analysis and conversion based on database semantics is proposed. The semantics of both the source and target databases are described in terms of entity types and their associations. The semantics of application programs is represented by an "application structure" of language sequences which correspond to a number of access path graphs representing the general access patterns associated with entity types and their associations. Program conversion is achieved by meaning-preserving transformations of the access path graphs to account for the various types of database changes.