A data model is a great way to und myerstand the structure of a system. It requires the acceptance of the concept of an “entity”. A data model depicts the relationships between the entities that make up a “real world” system. A data model differs from a mathematical model in that it neither requires mathematical provability nor must it be expressed in numbers and symwbols as a mathematical model does. A data model also differs from a process model in that it does not represent the dynamic changes in a system over time, it depicts the structure of a system, the way the parts of a system fit together.
A data model can be either a representation of the physical reality of a system or a non-physical representation. The latter is usually called either a “conceptual model” or a “logical model”. Though both of these phrases mean something non-physical they are not completely interchangeable with one another. A conceptual model is a model of ideas, while a logical model is a model of the semantic relationships between entities and requires a shared and agreed upon vocabulary for it to be useful.
Birkdale Computing 
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