Like your summary, it's primarily for communication with users and other stakeholders. You have entities, relationships, attributes, and domains. The implementation could be in some sort of prerelational database, or even in classical files of records. It is not bound to a relational implementation. The conceptual model summarizes the semantics of the data with reference to the subject matter. The way I learned it, back in the 1980s was this: The conceptual/logical/physical layers have changed somewhat over the years, and also vary according to different schools of thought. Using these definitions I would say that all you diagrams are versions of Conceptual Models as they do not include all the integrity constraints for the data being managed and do not include any information regarding an implementation on specific hardware or database management system. It may consist of information such as storage sizing and placement access methods such as indexing and distribution such as clustering or partitioning. In which case all the data structures and integrity constraints will be formally represented only using mathematical relations.Ī Physical Model (PM) is a representation of the LM on specific hardware and database management system. The LM may be presented as a Relational Data Model (RDM). It is database management system agnostic.
it should include all the data structures and integrity constraints for the data (this is all constraints, not just that subset of constraints that are easily defined in most available database management systems). It is often presented as Entity-Relationship Diagrams.Ī Logical Model (LM) formalizes the CM into data structures and integrity constraints. It will consist of classes of entities with attributes and the business rules regarding these.
A Conceptual Model (CM) is an informal representation of the business represented in a manner that is understood by users.
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