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WebSiteModel is the single Logical model and the MySql and SQLite models are the corresponding physical models.

One Logical and Multiple Physical Models

ER-Designer supports a hub and spoke, logical-physical database design model. A natural separation exists between the logical aspects of database schema and the physical DBMS specific implementation of the schema. The logical level elements can be shared across multiple different DBMS systems (e.g. SQLite, MySql) where as concrete physical properties that are DBMS specific cannot be shared.

ER-Designer exploits this natural separation between logical and physical schema designs to allow a single logical design to be implemented in multiple different physical DBMS systems. The screen snap shot on the right of ER-Designer's Model tree shows the logical model (WebSiteModel) and two DBMS specific models (MySql and SQLite).

A model merge system allows a DB architect to work at the logical level and a database application developer to work at the physical level, and have their work shared, merged, and deployed across multiple DBMS systems.

In addition to the logical-physical separation ER-Designer can perform conceptional transformations. As an example, shown in the following screen snap shots, is a logical non-specific relationship transformed into two relationships and an association table in the physical model.


A logical non-specific relationship is transformed into two physical non-identifying mandatory relationships and an association table.