Operation Conditions

Click the Conditions button on the Operation tab to open the Operation Conditions dialog box. Use this dialog box to configure options that verify that certain conditions, such as pre-conditions, required attributes, and/or error patterns, have been satisfied before an operation is evaluated during execution. The CheckOperationConditions command will fail if the condition fails during evaluation, which results in an operation exception at runtime. In order for these conditions to be verified, the CheckOperationConditions command is required as the first command in the operation. To cancel any changes and return to the default settings, click the Revert button.

The following options are available:

Pre-condition: Assigning a pre-condition to an operation means that the pre-condition will have to be satisfied in order for this operation to be executed. To create a pre-condition for this operation, click the Edit button to open the Condition Edit dialog box.
Required attributes: To require that certain attributes are written to before validation of an operation, select the Required check box for one or more attributes.
Error patterns: Error patterns enable you to set up user-defined errors in your model. A pattern is a candidate for being an error pattern if it is not considered to be part of an entity signature. By default, all auto-generated and manually created patterns are configured to be a part of the entity signature. In order to change this setting, clear the Use in entity signature box on the Pattern tab.

Tip: A good candidate for an error pattern might be an error message that appears on the terminal screen when a nonexistent account number is sent to the host.

The following options are available to configure error patterns:

Available—Select a pattern and click the right arrow button to add it to the Error patterns list.
Error patterns—Once a pattern becomes an error pattern, it is possible to create return text that is displayed when this pattern is encountered during an operation.
Return text—Select this option to create any return text that will be displayed if the error pattern is encountered during execution of this operation.
Return attribute contents—Select this option to return one or more attribute values as the contents of your error message. Select the attribute from the Unused list and click the right arrow button to add it to the Return list. You will see an exception of the type 'user defined' indicating that an error pattern was trapped, followed by the name of the pattern and the contents of the attribute. Attributes are returned in listed order.

Post-condition: Assigning a post-condition to an operation means that the post-condition will have to be satisfied after the operation has been executed in order for it to be evaluated during operation execution. If the post-condition fails during evaluation, an operation exception will be issued at runtime. To create a post-condition for an operation, click the Edit button to open the Condition Edit dialog box.