Rational Programming Patterns for System z

Meta Entity (Type) or Meta Data Aggregate composition

The composition of a Meta Entity or Méta Data must be done in the Composition tab, which is common to the Meta Entity, Meta Entity Type and Meta Data Aggregate editors. For the Meta Entities, the information entered in this tab helps you to define the structure of the User entities which are created from the current Meta Entity. In this window, you define the composition of the Meta Data Aggregates which are used then in Meta Entities, or to give the composition of a Meta Entity Type which is used to extend a Standard Entity.

About this task

A Meta Entity (Type) or Meta Data Aggregate have sometimes several levels of descriptions, that is, a description can call a child description, which can also call a child description, and so on. But all Meta Entity descriptions must have a root element of type 'DataAggregateDescription' or 'Pac Data Element'. The root element is unique and it is not possible to change its cardinality. In a root description of type 'DataAggregateDescription', you can have 'Data Aggregate Descriptions' with Data Element Descriptions, Pac Data Elements, and Meta Data Aggregates.

Procedure

  1. Open the Composition tab of an Entity. To do so, select a Meta Entity (Type)/Meta Data Aggregate in the Design Explorer view and double-click, or right-click and select Open. Then you can access the Composition tab from the Overview tab or by clicking directly the Composition tab in the Entity editor.
  2. For a Meta Entity or Meta Entity Type, if the description pane is empty, it means that no description has been added. If so, click Add and select Add Data Aggregate Description to create a description root. Enter a name for the description and a label in the definition pane which automatically opens up. For a Meta Data Aggregate, the root is created automatically, it takes the name of the Meta Data, and cannot be modified, neither deleted.
  3. Click again Add and select Add Data Aggregate Description to create the first Data Aggregate description, in which the Data Element Descriptions, Pac Data Elements and Meta Data Aggregates are included then.
  4. Then, click Add and select Add Data Element Description if you want to have Data Element Descriptions at this level of the tree structure. For a Data Element description, you must enter its type, its definition, its allowed values, and its intervals in the definition pane which shows up.
  5. To insert a Data Element call in the description tree, click Add and select Add Pac Data Element. A selection wizard opens up, you can click a Data Element instance or create a new one. When the Data Element displays in the composition tree. You do not have to enter any definition for this Data Element as it has been described and previously defined in the Data Element editor. You can also add Meta Data Aggregates by following the same procedure as for the Pac Data Elements.
  6. To create another level of description in the tree, click the Data Aggregate description root, then click Add, and select Add Data Aggregate Description. Give the description a name and a label in the definition pane. The number of descriptions in a Meta Entity/Meta Data Aggregate is unbounded.

What to do next

CAUTION:
Do not modify a Meta Entity when it contains User Entities. It may occur errors.

Do not forget to complete the fields in the definition panes which open up when you insert or select a composition line in the tree.


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