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ANSI Four Schema Model |
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A description of the four main types of data model originally created by ANSI in the 1970s. The model defines four categories of data model:
- External Schemas: A collection of inconsistent requirements from individual stakeholders
- Conceptual Schema: A consistent, but usually incomplete, consolidation of requirements
- Logical Data Model: A consistent and complete description independent of any particular implementation
- Physical Data Model: An implementation targeted at a particular technology (such as Oracle or an OODB)
Relation to Information Architecture
The task of data modelling has traditionally focused on the creation of efficient ways to represent the required information. Information Architecture's role in contrast is usually to define the constraints that the users impose on the eventual system.
This means that Information Architects must be careful to not indulge themselves in "data modelling", they must document what the users need, not how to provide it for them. Even if the person acting as the Information Architect and the Data Modeler are the same person a clear "separation of concerns" will help in the long run.
Links to this page
The following pages link to here: Conceptual Schema, Data Model, Data Modeling Language, External Schemas, Logical Data Model, Physical Data Model