1. Apparatus for monitoring transactions in a computer system, comprising: a processor, which is arranged to monitor events reported by components of the computer system responsively to a flow of the transactions through the system, to apply a state machine model to the monitored events so as to identify transaction-level events, to apply a rule-based model to the monitored events so as to identify business-level events, to perform at least one action selected from a group of actions consisting of modifying, responsively to at least one of the business-level events identified by the rule-based model, a first criterion applied by the state machine model in identifying one or more of the transaction-level events, and modifying, responsively to at least one of the transaction-level events identified by the state machine model, a second criterion applied by the rule-based model in identifying one or more of the business-level events, and to assess a status of the flow of the transactions responsively to the transaction-level events and the business-level events; and a user interface, which is arranged to interact with a user so as to permit the user to configure the state machine model and the rule-based model and to present the assessed status to the user.