When you use a workflow variable in an expression, the Integration Service evaluates the expression and returns True or False. If the condition evaluates to true, the Integration Service runs the next task. The Integration Service writes an entry in the workflow log similar to the following message:
INFO : LM_36506 : (1980|1040) Link [Session2 --> Session3]: condition is TRUE for the expression [$Session2.PrevTaskStatus = SUCCEEDED].
The Expression Editor displays the predefined workflow variables on the Predefined tab. The Workflow Manager groups task-specific variables by task and lists built-in variables under the Built-in node. To use a variable in an expression, double-click the variable. The Expression Editor displays task-specific variables in the Expression field in the following format: