Meta Entities and Meta Entity Types can be used to create
customized concepts that the metamodel does not manage in a standard
manner. Meta Entity Types extend all the model entities that are managed
by Rational Programming Patterns.
When a Meta Entity instance is defined and described, it is managed
as any other instance. User Entities are instances of a Meta Entity.
- Meta Entity and User Entity
- You can customize the information of a database to adapt it to
the specificity of your business. To do so, you must create your own
entities from Meta Entities and their instances, which are called
User instances.
- You must create a Meta Entity and define it. Then, you must describe
the structure of its User Entities in the Composition tab
of the Meta Entity editor. The description of a User Entity mirrors
the composition of the corresponding Meta Entity. In the Meta Entity,
you must define user relations for the fields that are defined with
a Reference type and that are linked to other
entities. User entities are managed in the same way as standard entities.
You can assign them keywords and comments. Each User Entity contains
a Description tab in which you enter the values
of the fields that are specified in the Meta Entity.
Example: For a Department Meta
Entity that contains two fields: Type of department and Number
of employees, you can define the Account User
Entity and specify Accounting department and 50
Employees.
- Meta Entity Type
- You can also create Meta Entity Type instances to extend standard
entities by adding descriptions to them. When a Meta Entity Type instance
is created, it is associated with the entity type that was specified
in the Meta Entity Type creation wizard. As a consequence, a new tab
is added to the editor of the extended entity. By default, it takes
the label of the Meta Entity Type or its name (if no label is specified).
A description tab is added to the editor of the extended entity for
each Meta Entity Type that is created for this entity type.
Example: To extend the description of the
Program entity, you can create two Meta Entity Type instances that
apply to the Program entity: Program 1 and Program
2. Two tabs are then added to the Program editor: Program
1 and Program 2. The description
is saved in the entity itself, so you do not need to create a User
Entity. The tab that extends the entity description is the same as
the description tab of a User Entity.
- Meta Entity Type "CR"
- This Meta Entity applies to the Pacbase facet only.
If
you migrate a Pacbase database,
a Database_Name.INTER project is automatically
created at the root of all the projects when the ta2 file
is imported. The project can then be shared by all the other projects.
It contains an instance of the Meta Entity Type "CR", which is
the standard structure that is used by all the entities to add references
between entities. Its description is available in the editors of all
the entities with the CR Lines tab. With this
tab, you can add new references that are not defined in the design
of entities. The contents of CR Lines in the INTER project
can be modified by an administrator only who can add fields but cannot
delete the required fields. However, it is forbidden to modify the Composition tab
in the Meta Entity Type CR.
- Meta Data Aggregate
- To create a hierarchy of data that can be used in several Meta
Entities, you can create Meta Data Aggregates. You create, define,
and describe them as Meta Entities. Then, you can reuse them in Meta
Entities or Meta Entity Types.
When you create a Meta Data Aggregate,
a root is automatically inserted in the Composition tab
of the Meta Data Aggregate editor. By default, it takes the name of
the Meta Data Aggregate. It cannot be modified or deleted.
Example of a Meta Data Aggregate reuse in a Meta Entity: - A Meta Data Aggregate Address,
- A Meta Entity Customer with two fields: Name and Address,
- A Meta Entity Seller with two fields: Name and Address.