The Meta Entity helps you to create your own customized
concepts that the metamodel does not handle in a standard manner.
There are different types of Meta Entities: Meta Entity Type, User
Entity, Meta Data Aggregate. When a Meta Entity instance is defined
and described, it is handled as any other Pac instance. User Entities
are instances of a given Meta Entity.
- META ENTITY TYPE 'CR'
- When a ta2 file is imported in a workspace, a project Database_Name.INTER is
created automatically at the root of all projects. Thus, the project
can be shared by all other projects. It contains an instance of Meta
Entity Type named "CR", which is the standard structure used
by all entities to add references between entities. Its description
is available in the editors of all entities with the tab CR
Lines. 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
only by an administrator who can add new fields but cannot delete
existing fields which are required. But it is forbidden to modify
the Composition tab in the Meta Entity Type
CR.
- META ENTITY/USER ENTITY
- You can customize the information saved in a database to adapt
it to the specificity of your business by creating new entities: Meta
Entities and User instances, which are the instances of Meta Entities.
- You must create a Meta Entity first and then describe the structure
of its User Entities in the Composition tab
of the Meta Entity editor. The description of a User Entity entirely
depends on the composition of the corresponding Meta Entity defined
by the user. In the Meta Entity you must define User relations for
the fields included in a User Entity and defined with a Reference
type in the Meta Entity it is related to. User entities are managed
in the same way as standard entities. You can assign them keywords
and comments. For each User Entity, you can enter values in the description
tab for each component entered in the associated Meta Entity.
Example: For a Meta Entity "Service" containing
two Data Elements: "Type of service" and "Number of employees",
you can define the User Entity "Info" which can be completed
as follows: "Computing Service" and "50 Employees".
- META ENTITY TYPE
- You can also create Meta Entity Type instances to extend Pac standard
entities and thus add descriptions to an entity Type. When a Meta
Entity Type instance is created, it is associated with the type of
Pac entity that you defined in the Meta Entity Type creation wizard.
As a consequence, a new tab is added to the editor of the extended
Pac entity. By default, it takes the label of the Meta Entity Type,
or its name if no label is specified. There are as many description
tabs added to the extended entity editor as Meta Entity Type instances
created for this entity type.
Example: If
you want to extend the description of a Program entity and if you
create two Meta Entity Type instances ("Program 1" and "Program
2") which apply to the Pac Program entity, you find then in the
Program editor two additional tabs ("Program 1" and "Program
2") . The descriptions are saved in the entity itself, so you do
not need to create a User Entity. The tab corresponding to the extension
of the entity description is the same as the description tab of a
User Entity.
- META DATA AGGREGATE
- To create a hierarchy of data that is to be used in several Meta
Entities you can create Meta Data Aggregates. These are entities that
you create, define, and compose as you do for Meta Entities. When
it has been defined and described, you can reuse a Meta Data Aggregate
in your Meta Entities or in your Meta Entity Type. However, a Meta
Data Aggregate contains a specificity, as when you create a Meta Data,
a root is automatically inserted in the Composition tab
of the Meta Data editor. This root is given the name of the Meta Data
Aggregate by default, and it cannot be modified nor deleted.
Example of Meta Data Aggregate reuse in a Meta Entity: - A Meta Data Aggregate "Address"
- A Meta Entity "Customer" with two fields "Name" and "Address"
- And a Meta Entity "Seller" with two fields "Name" and "Address"