Online Documentation for SQL Administrator for SQL Server
Precedence constraints
Use the Precedence constraints section to establish relationships between the tasks.
Preceding executables
In this area define tasks after which the configured maintenance task should run.
After that choose whether 
To execute the task all constraints must be True (Logical AND) or To execute the task one constraint must be True (Logical OR).
Subsequent executables
Here define tasks that should run after the configured maintenance task.
Using the context menu of both areas you can:
Add a new constraint
Edit an existing constraint
Delete constraint
Alternatively, you can use the 'Insert' button to create a constraint, 'Enter' button to edit constraint and 'Delete' button to drop a constraint.
The second task (the Constrained executable) executes only if the execution result of the first task (the Preceding executable) matches specified criteria. You can set this criteria by checking the 
Preceding execution result is and/or Expression evaluates to True.
The execution result may be specified as Success, Failure or Completion.
Success requires that the precedence executable succeed, Failure requires that the precedence executable fail, and Completion indicates that the constrained executable should run regardless of whether the precedence task succeeds or fails.
Expression evaluates to True
An expression that is evaluated to determine whether the constrained executable runs. If the expression evaluates to true, the constrained executable runs.
See also:
