Data Items (CDM)

A data item is an elementary piece of information, which represents a fact or a definition in an information system, and which may or may not have any eventual existence as a modeled object.

You can attach a data item to an entity (see Entities (CDM/LDM) ) in order to create an entity attribute (see Attributes (CDM/LDM)), which is associated with the data item.

There is no requirement to attach a data item to an entity. It remains defined in the model and can be attached to an entity at any time.

Data items are not generated when you generate an LDM or PDM.

Example

In the information system for a publishing company, the last names for authors and customers are both important pieces of business information. The data item LAST NAME is created to represent this information. It is attached to the entities AUTHOR and CUSTOMER, and becomes entity attributes of those entities.

Another piece of information is the date of birth of each author. The data item BIRTH DATE is created but, as there is no immediate need for this information in the model, it is not attached to any entity.

Creating a Data Item
You can create a data item from the Browser or Model menu. Data items are automatically created when you create entity attributes.
Data Item Properties
To view or edit a data item's properties, double-click its Browser or list entry. The property sheet tabs and fields listed here are those available by default, before any customization of the interface by you or an administrator.
Controlling Uniqueness and Reuse of Data Items
You can control naming restraints and reuse for data items with CDM model options, by selecting ToolsModel Options .

Parent topic: Conceptual and Logical Diagrams