Data modeling: Difference between revisions

Revision as of 23:33, 26 February 2006

Revision as of 09:06, 28 February 2006

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Structured data is described by data models. In the early phases of a software development project, emphasis will be on the design of a [[conceptual schema|conceptual data model]]. This can be detailed into a [[logical data model]] sometimes called a [[functional data model]]. In later stages, this model may be translated into [[physical data model]].

The term ''data modeling'' actually refers to two very different things. In the first sense, a data model is a description of the structure of the data within a given ___domain of concern, and by implication of the underlying structure of that ___domain itself. For example, a model may representsrepresent classes of things of significance about which a company wishes to hold information (''entity classes''), the nature of that information (''attributes''"), and relationships among those things. The organization of data presented is all about describing the organization and is not concerned with how data might be represented in a computer system.

The entity classes represented can be the tangible things seen by the people in the business, but these tend to be very concrete and subject to change over time. A more robust approach is "conceptual" identifying more fundamental things of significance--of which the things the business sees are examples. For example, an entity class that might appear in a given model is PERSON, representing all the people that an organization is concerned with. [NOTE: Except for the word "NOTE" words in all capital letters refer to entity class names.] Entity classes like VENDOR and EMPLOYEE are not appropriate, because each of these describes a role played by a PERSON not the person themself.