Conceptual, Logical, Physical Design Models PDF

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Conceptual, Logical, and Physical Models

Conceptual model

Logical model

Physical model

We can see that the complexity increases from conceptual to logical to physical. This is why we always first start with the conceptual data model (so we understand at high level what are the different entities in our data and how they relate to one another), then move on to the logical data model (so we understand the details of our data without worrying about how they will actually implemented), and finally the physical data model (so we know exactly how to implement our data model in the database of choice). In a data warehousing project, sometimes the conceptual data model and the logical data model are considered as a single deliverable. Database Design Cycle The figure below shows the key tasks and deliverables in the overall task of database design, of which data modeling is a part. Note that this diagram is a deliberate over-simplification of what is involved; each task shown is inevitably iterative, involving at least one cycle of review and modification.

In the figure you can see that there are three different data models produced as we progress from business requirements to a complete database specification. The conceptual data model is a (relatively) technologyindependent specification of the data to be held in the database. It is the focus of communication between the data modeler and business stakeholders, and it is usually presented as a diagram with supporting documentation. The logical data model is a translation of the conceptual model into structures that can be implemented using a database management system (DBMS). Today, that usually means that this model specifies tables and columns, as we saw in our first example. These are the basic building blocks of relational databases, which are implemented using a relational database management system (RDBMS). The physical data model incorporates any changes necessary to achieve adequate performance and is also presented in terms of tables and columns, together with a specification of physical storage (which may include data distribution) and access mechanisms....