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The "Theory" section covers conceptual and logical models for data warehouse design. To get a detailed description about the different models, please choose a model from the list below:

These models may be classified according to the following 3-layer design schema:

Figure M.1 - The three abstraction layers

Conceptual models ("Dimensional Fact Model" and "Aggregation Path Array") represent an abstraction of the real world. Various objects, their attributes and relationships are selected to construct a simplified view of reality. Conceptual models are completely independent from the database used in the implementation, they represent the user's point of view. The Entity-Relationship Model is an example for a common, non-data-warehouse-specific conceptual design method.

Logical models ("Star Schema" and its derivatives) are a representation of the structure of the data stored, they depend on the type of database used. The dominant logical model is the relational model.

Physical models (not covered by this webtrainer) describe the physical implementation of the database itself using indices, pointers, directories, and other structures for building database systems. They depend on the database application chosen for implementation as well as the storage media used.