Building a Data Model - High-Performance Web Databases: Design, Development, and Deployment - page 216

Exhibit 14-3. ANSI/X3/SPARC three-schema architecture.
property he or she is renting. It probably would include more details about
that one property, such as days for garbage pickup and location of the
nearest liquor store.
As the integrated view of all the business's data, the conceptual schema
is a consolidation of all relevant data models. A conceptual schema can be
developed as a prerequisite deliverable before implementing any data-
bases. Or, more practically, a conceptual schema can evolve by consolidat-
ing data models as they are built. The conceptual schema will help ensure
consistency of multiple data models, defined to support different user
groups or different areas of the business. Existence of one (even evolving)
conceptual schema will also aid in designing shared databases or internal
schemas that support multiple external schemas. Finally, the conceptual
schema will help ensure consistency across multiple database implemen-
tations or internal schemas (e.g., making use of different technological
strengths). Thus, a user can maintain one view (one external schema) of
the data regardless of underlying implementations (internal schemas).