A method and system that enables data to be shared across application systems via a table substitution scheme. Tables are identified in the legacy application system that are candidates for substitution of tables in the core application system containing similar data. Table structure meta data corresponding to these "substituted" tables are then extracted from the legacy system schema, and stored in a repository. In accordance with the meta data, business logic is defined to remap columns in the core tables to corresponding columns in the substituted tables. Accordingly, when the core application system performs data access (e.g., reads, inserts, updates, etc.), it accesses the remapped columns in the substituted tables instead of original columns in the core tables. At the same time, the legacy application system is enabled to concurrently access the substituted tables without require any changes to the business logic of the legacy application system.