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.
The NSV-11b Report Template
The NSV-11b report template uses two parameters:
• The Architecture parameter, which identifies the architecture to be analyzed.
• The Database Subset parameter, which is optional. This parameter is used to reduce the scope of the study to a subset of the databases defined in the architecture. If this parameter is not set, all the databases defined in the architecture are taken into account.
The NSV-11b Physical Data Model Chapter
The Physical Data Model chapter lists the databases modeled to support the storage of data with their tables and column details.
A database table is first displayed with the short name, long name and comment of each database.
• A paragraph is dedicated to each database. This paragraph includes:
• The comment of the database.
• The diagrams describing the databases.
• The associated data models.
• The list of tables contained in the databases. This list is a table with the short name, the long name and the comment of each table contained in the database.
The database paragraphs are followed by the table paragraphs. Each table which has one of the following items is inserted in a dedicated paragraph with:
• The comment of the table.
• The list of columns (name and comment).
• The list of indexes (name and comment).
• The list of keys (name and comment).