The Identity type attribute supports automatic generation of integer values according to a Sequence ID specified when the attribute is created. The Sequence ID is an alpha-numerical identifier. The values generated will be unique within the specified sequence.
The Sequence ID must always be specified for an identify attribute.
Defining a Sequence Without any Formatting
To generate an integer value without any prefix or other formatting, simply enter 'Counter' in Sequence id.
Defining a Sequence With Formatting
Using a prefix and a separator (such as a hyphen) between a prefix and the integer is optional and would be defined as follows:
<Prefix string> + "-" + <Sequence identifier>
In other words, the prefix will come first, followed by a hyphen symbol, and the integer value will come last. The value displayed in the Explorer client will include the prefix, hyphen and identifier.
Example String Definition
Things to Consider
- Identity attributes cannot be cloned. Objects created via cloning will get new, unique values.
- Default values cannot be specified.
- The "Allow empty value" option does not apply to identity attributes. The values are always auto-generated.
- Identity attributes cannot be imported as an identity attribute ("You cannot explicitly set values of identity attributes"). Because they are auto-generated, it would cause a problem if you imported, for example, an ID=1 when there already exists an ID=1 in the target database. To import an identity attribute, you must first create a string-type attribute in your target meta model and then import the identity attribute values to the new string attribute via mapping in the XML import file.