The standardization and broad adoption of Service Oriented Architectures, Web Services, and Cloud Computing is raising the complexity of ICT systems. Hence, assuring correct system behavior with regard to established design and business constraints is of the utmost importance. Run-time monitoring, where the outcomes of an observed system are continuously checked against what is expected of it, is one possible approach to providing the required oversight. In this paper, we discuss this notion of rule expectations, their violation and/or fulfillment, and use these concepts to define the concept of an Event-Condition-Expectation (ECE-) rule, a variation of the traditional Event-Condition-Action rule pattern. To demonstrate these concepts, we present extensions to the syntax used by the production rule engine, Drools, and describe their use in a medical case study. The clinical decision support system being developed monitors rule evaluations and expectations, detects constraint violations and is able to take recovery/ compensation actions as appropriate.