What Is a Data Model

A data model is a great way to understand 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 symbols 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 useful.  In building software that processes data, whether it’s a game, an accounting system, a machine learning model, a transportation guidance system, or anything else you can use a computer to do, all three models end up being produced whether explicitly or not. Sometimes the conceptual and logical models are only in the minds of the people who produce the software, and sometimes they are explicitly documented as part of the history of construction.  Even explicit physical data models are not always produced.   As long as a system processes data a data model will be part of the system, implied or explicit. 


One problem of non-explicit models is that the knowledge of the relationships between the parts of a system may be lost and have to be re-discovered everytime work is required to be done on the system, either to correct errors, expand it functionality, or to replace the system altogether. Six Basic Interrogatives (6BI) organizes the process of data modeling into six Business Object Categories (BOC’s) which are mutually exclusive categories of entities that give framework for answering any question that may be asked of the system.  Does it give the answers … No.  It provides a semantic framework so that answers can be shared and the concepts expressed in the answers can be compared both between systems and within a system.

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