Chapter 2 Conceptual Data Model Basics

Setting Model Settings

To set Model Settings, select Tools→Model Options or right-click the diagram background and select Model Options from the contextual menu.


The options on this tab affect all the objects in the model, including those already created, while changes to the object-specific options on the sub-category tabs only affect objects created subsequently.

You can set the following options on this tab:

All Objects

Option Description
Name/Code case sensitive You can define the case sensitivity of names and codes for all objects in the current model. When this check box is selected, it implies that you can have two objects with identical name or code but different case in the same namespace.

Unlike other model options, you can modify the name and code case sensitivity during the design process. However, if you do so, make sure you run the check model feature to verify if the model does not contain any duplicate object.
Enable links to requirements Requirements are descriptions of customer needs that must be satisfied during development processes.

You can enable links to requirements for all objects in the current model. When this check box is selected, it implies that the Requirements tab is displayed in the objects property sheet. The Requirements page allows you to attach requirements to objects; these requirements are defined in the Requirements models open in the workspace. Attached requirements and Requirements models are synchronized.

For more information on requirements, see the Requirements Model User's Guide .

Notation

You can choose to use one or both of the following notation types in the current model:

Option Description
Entity / Relationships [Default – used throughout this manual] Entity/relationship notation connects entities with links representing one of four relationships between them. These relationships have properties that apply to both entities involved in the relationship
Merise Merise notation uses associations instead of relationships
E/R + Merise Both entity/relationship and Merise are used in the same model
IDEF1X Data modeling notation for relationships and entities. In this notation, each set of relationship symbols describes a combination of the optionality and cardinality of the entity next to it

When you change notation, all symbols in all diagrams are updated accordingly.

For the IDEF1X notation:

Cardinality Representation
One - Many
One - One or Many - Many
One - One dependent displays a continuous line and entity with rounded angles

PowerDesigner does not support the following notation:


or


Sub-type or inheritance symbol changes according to the Complete property:

Complete Symbol
Yes
No

Data Item

Option Description
Unique code Requires that data items have unique codes
Allow reuse 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

When you delete an entity or entity attributes, these options determine whether or not the corresponding data items are also deleted, as follows:

Options set Result of deleting an entity attribute
Both Deletes the entity attribute.
Unique Code only Deletes the entity attribute.
Allow Reuse only Deletes the entity attribute and the corresponding data item (if it is not used by another entity).
None Deletes the entity attribute and the corresponding data item.

Relationship

Option Description
Unique code Requires that relationships have unique codes.

Domain / Attribute

Option Description
Enforce non-divergence Enforces non-divergence between a domain definition and the attributes using the domain. You can select any or all of the following attribute properties:

  • Data type - Data type, length, and precision
  • Check - Check parameters, such as minimum and maximum values
  • Rules - Business rules
  • Mandatory - Entity, association and inheritance attribute mandatory property


When you apply the Enforce non-divergence options You are asked if you want to apply domain properties to attributes currently attached to the domain. If you click OK, the attribute properties are modified in order to be consistent with the properties of the domain to which they belong.



When you modify the properties of a domain The properties of the attributes attached to the domain are updated provided these properties are selected in the Model Options dialog box.



Attributes cannot be modified When you select an attribute property under Enforce non-divergence, each instance of that attribute property in the lists of attributes and the property sheets of attributes is displayed as unavailable and can not be modified.



If you want to modify an attribute property that is defined as non-divergent, you must detach the attribute from its domain, or clear the appropriate Enforce non-divergence model option.
Use data type full name Specifies that the complete data type is displayed in entity symbols.
Default data type Specifies a default data type to apply to domains and attributes if none is selected for them.

 

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