Limitations in the current Implementation

The current implementation of active rules in ConceptBase has several limitations.

• The dependency graph of ECA rules may contain cycles, i.e. rule R1 executes an action, which fires the rule R2 and R2 has an action which fires R1. The current algorithm for detecting cycles tests the dependency graph during compile time. The cycle checker prints a warning message on the console if it has detected a possible cycle, but the compilation of the rule is not aborted, because it is still possible that the cycle does not occur during the execution of the rule. The user must take care, that cycles are avoided.
• Because of the current transaction processing of ConceptBase, it is not possible to use Tell and Untell events and actions in any combination, i.e. you can not tell and untell the same object in one transaction.
• Instantiations and specializations of system classes (Proposition, Attribute, InstanceOf, ...) are not detected in the event manager. We don't think, that this is a real problem, because an ECArule with a system class in the event expression does not make sense.
• As QueryClasses, ECArules can not be updated after they have been telled (e.g. change the event, condition or actions). The only updateable attribute of ECArule is active. If you set this attribute to FALSE, you can deactivate the rule for a certain time. Deleting or setting the attribute to TRUE re-activates the ECArule. If you don't want to use an ECArule anymore, you can untell it.