NSV-11b Physical Data Model
The Physical data model is used for the analysis of a system's data implementation aspect, with consideration for a specific product. They can also be used to:
• Provide as much detail as possible on the data elements exchanged between systems to reduce the risk of interoperability problems.
• Provide the data structures for use in the system design process, if necessary.
• Provide a common dictionary of data implementation elements (e.g. tables and records in a relational database schema) to consistently express subviews wherever physical-level data elements are included in the descriptions.
The physical data model specifies how the logical data model will be instantiated in a particular product. The most predominant of such products are the relational database management systems, such as those supplied by Oracle and Microsoft (in which case the physical data model is often called a 'database schema'). Object repository products also exist, but are less often encountered.
The essential elements of a physical data model (in the case of a relational database) are: tables, records and keys. In a true object-oriented data model, all data elements are expressed as objects; whether they are classes, instances, attributes, relationships, or events.