Levels of a data model

There are three different levels of Data Model, this makes the model either at a very broad and high level conceptual view, or a more detailed logical or physical view.

The levels of different models are given below,

1. Conceptual data model (CDM) or Subject area model (SAM).
2. Logical data model (LDM).
3. Physical Data Model (PDM).

Let us briefly look about these models in this post, each of this level of models will be discussed in details in the future posts.

Conceptual Data Model (CDM) 

A conceptual data model or subject area model (SAM) represents the business at very high level. It is a very broad view containing only the basic and critical concepts for a given scope. Here, basic means that the subject area is usually mentioned a hundred times a day in normal conversation. Critical means that without this subject area scope of the data model would be greatly changed. Some subjects areas are common to all organisations, such as Product, Customer and Employee. Other subject are very industry or department specific such as Raw Materials for Manufacturing Industry.

Logical Data Model (LDM)

A logical data model (LDM) represents a detailed business solution. It is how the modeler captures the business requirements without complicating the model with implementation concerns such as software and hardware.

Physical Data Model (PDM)

A physical data model (PDM) represents a detailed technology solution. PDM which is the 'incarnation' or 'instantiation' of the LDM, the Logical data model usually needs to be modified to make it usable. A PDM is optimized for a specific context (such as specific software or hardware). A physical data model is the logical data model modified with performance-enhancing techniques for the specific environment in which the data will be created, maintained and accessed.

I hope this post will give you an basic understanding of the different levels of data model, in the next post let us discuss about the entities in data model.