Data item

Chapter 2 Conceptual Data Model Basics

Data item

You can choose to use one or both of the following data item options in the current model:

Option	Description
Unique code	When selected, requires that data items have unique codes
Allow reuse	When selected, makes it possible to reuse one data item as an attribute for more than one entity provided the attributes have same name and data type and do not belong to a primary key. When deselected or when the attribute belongs to a primary key, the data item cannot be reused. In this case, if the Unique code check box is selected, a new data item with identical name but different code is created, otherwise a new data item with identical name and code is created

Option

Description

Unique code

When selected, requires that data items have unique codes

Allow reuse

When selected, makes it possible to reuse one data item as an attribute for more than one entity provided the attributes have same name and data type and do not belong to a primary key.

When deselected or when the attribute belongs to a primary key, the data item cannot be reused. In this case, if the Unique code check box is selected, a new data item with identical name but different code is created, otherwise a new data item with identical name and code is created

Deleting entity attributes

When you delete an entity or entity attributes, data item options determine whether or not the corresponding data items are also deleted.

The following rules apply to deleted entity attributes:

Data item options	Result of deleting an entity attribute
Unique Code Allow Reuse	Deletes entity attribute Does not delete corresponding data item
Unique Code only	Deletes entity attribute Does not delete corresponding data item
Allow Reuse only	Deletes entity attribute Deletes corresponding data item if it is not used by another entity
None	Deletes entity attribute Deletes corresponding data item