ER/Studio - Embarcadero Technologies Product Documentation

USING ER/STUDIO > WORKING WITH THE DATA DICTIONARY
Domains are reusable attribute templates that promote consistent domain definitions. You construct domains as you
would attributes, specifying a name, datatype properties, null status, default values and validation rules. After creating
domains, you can re-use them in your data model by applying them to attributes and table columns. By defining a
domain, you also gain the power of propagating changes to the underlying domain definition to all attributes and table
columns that reference it.
One important method for enforcing business rules is to define and to apply domain restrictions. Domain integrity
refers to the rules governing what values an attribute can take. By restricting and validating an attribute’s values, you
can implement important business rules such as ensuring that a checking account maintains a positive balance, or
preventing the entry of invalid phone numbers.
ER/Studio lets you organize your domains using domain folders. Domain folders let you create and manage your Data
Dictionary Domains. You can classify domains in unique groups by creating different domain folders. You can create
nodes within nodes. You can move existing domains into a domain folder, or create new domains within the folder.
Domains can be dragged and dropped into a table or entity to create a column or attribute. Domains can also be
dragged onto another domain to create a subdomain, by moving the selected domain beneath the target domain.
Domains can also be copied and pasted onto another domain to create a copy of the selected domain as a subdomain
or the target domain. Note, changes to the copied domain will not be inherited by the pasted subdomain.
Domains can have nested subdomains or child domains that initially duplicate most of the attributes of the parent
domain, but can have divergent behaviors once created. A Domain Override option in the Add Domain or Edit Domain
functions creates inheritance and overrides the domain system without losing the valuable relationship with the
attributes/columns (binding information).
NOTE: When you delete a domain folder, all domains and folders within that folder are also deleted. All
bindings to any columns and attributes are unbound.
Create a Domain Folder
1 On the Data Dictionary tab, right-click the Domains node and then click New Domain Folder.
2 Enter a name for the domain and then click OK.
Create and Edit a Domain or Subdomain
1 To create a domain at the root of the Domains node, on the Data Dictionary tab, right-click the Domains node
and then click New Domain.
To create a domain within a domain folder, on the Data Dictionary tab, expand the Domains node, right-click
the node of a domain folder, and then click New Domain.
To create a subdomain (a domain within a domain folder), on the Data Dictionary tab, navigate to the domain
folder where you want to create the subdomain, right-click the domain folder, and then click New Domain.
2 Define the domain as required and then click OK to complete the editor.
TIP: Once created, you can edit the domain by double-clicking its object on the Data Dictionary tab to
launch the editor.
The following describe options that require additional explanation
Datatype tab
• Receive Parent Modifications: For subdomains, lets you synchronize changes made to the attributes of a
parent domain with a those of the child domain. Selecting this option automatically synchronizes parent and child
attributes, except those specified on the Reference Values, Naming Standards, Attachment Binding, and Binding
Information tabs. Not selecting this option creates a child domain that is initially identical to the parent domain,
except that the child domain is created without any attachment bindings. Subsequent changes to the parent
domain will not be inherited by the subdomain. Any changes you make to the subdomain will override the values
inherited from the parent domain. Henceforth, the child can only inherit attributes from the parent if these
attributes were not previously specified for the child.
EMBARCADERO TECHNOLOGIES > ER/STUDIO® 8.0.3 USER GUIDE 234