Role of Transformations in Supertype-Subtype Relationships
A subtype relationship is a relationship between a supertype entity and a subtype entity. You can use a subtype relationship to create a hierarchical grouping of entities that share common characteristics.
When you transition from one design layer to another, or when you change a model over time, the way that you represent subtype relationships can change. You can apply a transformation to create an identifying relationship between a supertype entity and its subtype entities.
The main reasons why you apply a transformation to create an identifying relationship between a supertype entity and its subtype entities include:
- You want to simplify a model.
- The subtype relationship is not appropriate for the current design layer.
- You want to improve query performance.
The Supertype Subtype Identity transformation can be applied on an existing subtype relationship in a logical-only model, or the logical view of a logical/physical model. When you create or resolve a Supertype Subtype Identity transformation, the identifying relationships are preserved and the subtype symbol is deleted. No attribute or column is affected by the transformation. The preserved identifying relationships can be viewed in either the logical or physical model view.
Resolve to Supertype-Subtype Identity Wizard
To create an identifying relationship between a supertype entity and its subtype entities, you select the subtype relationship symbol 
, and click the Supertype-Subtype Identity 
icon on the Transformations toolbar.
Result of Creating an Identifying Relationship
When you click the Resolve to Supertype-Subtype Identity to create an identifying relationship between a supertype entity and its subtype entities, you:
- Convert the subtype relationships to identifying relationships.
|
Copyright © 2023 Quest Software, Inc. |