We describe the Monitoring-aided Checking and Steering (MaCS) framework
that assures the correctness of software execution at run-time.
Checking is performed based on a formal specification of system requirements
to ensure that the current system behavior is in compliance with these
requirements. When the system behavior violates these requirements,steering
is innvoked to correct the system. Our framework bridges the gap between
formal verification and testing. The former is used to ensure the correctness
of a design specification rather than an implementation, whereas the latter is
used to validate an implementation. The paper presents an overview of the
framework and the three scripting languages, which are used to specify what
to observe from the running program, the requirements that the program should
satisfy and how to steer the running program to a safe state. An important
aspect of the framework is clear separation between the 
implementation-dependent
description of monitored objects and the high-level requiremennts
specification. Another saliennt feature is automatic instrumentation of
executable code for monitoring and steering. This paper also describes
our current prototype implemenntation n Janva.