On Systematic Design of Protectors for Employing Ots Items on Systematic Design of Protectors for Employing Ots Items

Off-the-shelf (OTS) components are increasingly used in application areas with stringent dependability requirements. Component wrapping is a well known structuring technique used in many areas. We propose a general approach to developing protective wrappers that assist in integrating OTS items with a focus on the overall system dependability. The wrappers are viewed as redundant software employed to detect errors or suspicious activity and to execute appropriate recovery when possible; wrapper development is considered as a part of system integration. Wrappers are to be rigorously specified and executed at run time as a means of protecting OTS items against faults in the rest of the system, and the system against the OTS item's faults. Possible symptoms of erroneous behaviour to be detected by a protective wrapper are classified and a list of possible actions to be undertaken is discussed. The information required for the wrapper development is provided by traceability analysis. Possible approaches to implementing " protectors " in the standard component technologies are briefly outlined.