Dimensional Data Modeling - Semantic Layer
About
A semantic layer is a semantic data model that shows to the business user:
It will create/model a logical star schema by:
- tagging:
- the tables as dimension or fact table
- the columns as measure or description
- creating derived measure (calculation)
- defining:
- the relationship between tables
- the dimensional hierarchy and its level
Once the semantic layer has been build, the business user will see a logical star schema that it can query (business query). This query is called a semantic query.
The semantic layer will translate:
- to a sql query.
It's a key components of business intelligence / data analysis application because it provides a translation of the underlying database structures into business user oriented terms (such as revenue by year, …)
Articles Related
Example
- the logical business model for OBIEE,
- the universes for Business Object
Data Modeling Issue
While modeling the semantic layer, the developer can fall in different issues. See Semantic Layer Modeling - Issues (SQL Trap)