Artifact: Data Model

Data Model	The data model is a subset of the implementation model which describes the logical and physical representation of persistent data in the system. It also includes any behavior defined in the database, such as stored procedures, triggers, constraints, and so forth.
UML representation:	A top-level Package stereotyped as «data model», containing a set of Components which represent the physical storage of persistent data in the system.
Role:	Database Designer
More information:	Guidelines:Data Model Guidelines:Reverse-engineering Relational Databases Checkpoints:Data Model
Optionality:	Optional if the system has no persistent data
Purpose Properties Timing Responsibility Tailoring

Input to Activities:

Identify Targets of Test

Identify Test Ideas

Implement Component

Database Design

Output from Activities:

Database Design

Purpose

The data model is used to describe the logical and possibly physical structure of the persistent information managed by the system. The data model is specifically needed where the persistent data structure cannot be automatically and mechanically derived from the structure of persistent classes in the design model. It is used to define the mapping between persistent design classes and persistent data structures, and to define the persistent data structures themselves. It is most frequently needed when the design model is an object model and the persistent storage mechanism is based upon a relational database, although it is generally needed whenever the persistent storage mechanism is based upon some non-object-oriented technology.

Properties

Property Name	Brief Description	UML Representation
Introduction	A textual description that serves as a brief introduction to the model.	Tagged value, of type "short text".
Packages	The packages used for organizational grouping purposes.	Owned via the association "represents", or recursively via the aggregation "owns".
Tables	The tables in the data model, owned by the packages.	Components, stereotyped as «table».
Relationships	The relationships between tables in the model.	Associations, stereotyped as «foreign key».
Columns	The data values of the tables.	Attributes, stereotyped as «column».
Diagrams	The diagrams in the model, owned by the packages.	- " -
Indexes	Data access structures used to speed access along specified paths.	Components, stereotyped as «index».
Triggers	Event-activated behavior associated with tables.	Operation, stereotyped as «trigger».
Procedures	Explicitly invoked behavior, associated with tables or with the model as a whole.	Component, stereotyped as «procedure».

Timing

The Data Model is created in the Elaboration phase, based upon architecturally significant persistent classes. The Data Model is refined and expanded during the Construction phase.

Responsibility

A database designer is responsible for the integrity of the data model, ensuring that the data model as a whole is correct, consistent, and understandable.

Tailoring

Needs to be adapted to the semantics of the database, which may vary slightly between RDBMSes. Object Database systems have quite different semantics and the model described above needs to be modified accordingly.