Chapter 4 Building Conceptual Data Models


Using a data item as an entity attribute

You can use the data item as an entity attribute by attaching it to an entity. This choice does not create a new data item. The resulting entity attribute has the same code as the data item.

Reusing a data item as an entity attribute

If you select Allow Reuse as a data item option, the same data item can be an entity attribute for more than one entity. However, you cannot reuse a data item that is an identifier.

Reusing a data item does not create a new data item. The data item and the corresponding entity attributes have the same code.

Note   Setting data item options
You set data item options by selecting Tools→Model Options.

A new data item can be added by creating a new one or copying an existing one as the basis for a new one. The following specific tools are available to add data items:

Tool Description/Effect of Model Options
Add Data Item This tool is only available if the Allow Reuse option is selected in Model Options.

This tool displays all model data items. If you click this tool and select a data item that is unused in the list of entity attributes, a new data item is created and added to the list.

If you click this tool and select a currently used data item, the data item is copied and used as the basis for a new data item
Reuse Data Item No new unused data item can be created with this tool.

This tool displays all model data items. If you click this tool and select a data item that is used in the list of entity attributes, the data item is copied, added to the list and used as the basis for a new data item

Steps To use a data item as an entity attribute:

  1. Select the Attributes tab in the entity property sheet to display the corresponding page.

    It lists entity attributes associated with the entity.
  2. Click the Add Data Item tool.

    A Selection box appears listing all of the available data items.
  3. Select one or more data items.
  4. Click OK.

    The selected data items are added to the list of entity attributes.
  5. Click OK in each of the dialog boxes.

 


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