Unintended function

Computer Virus A program that alters other programs to include a copy of itself and executes when the host program is executed. The execution of a virus program compromises a computer system by performing unwanted or unintended functions that may be destructive. [Defined for this book.]... 

Requirements are necessary (i.e., limit the potential for unintended functions in the system or for unintended functions to be induced in interfacing systems. 

Verification demonstrates intended function and confidence of no unintended function impacts to safety. 

Each software module shall be checked with a process review, simulation and testing (i.e., dynamic analysis and white box testing when the source code is available with test cases from boundary value analysis) to determine that the intended function is correctly executed and unintended functions not are executed. 

The application software tests shall verify that all of the application software modules and com-ponents/subsystem interact correctly with each other and with underlying embedded software to perform their intended function and do not perform unintended functions. 

The SRECS shall be integrated according to the specified SRECS design. As part of the integration of all subsystems and subsystem elements into the SRECS, the SRECS shall be tested according to the specified integration tests. These tests shall verify that all modules interact correctly to perform their intended function and not perform unintended functions. 

NOTE Tests should also be carried out to oonfirm that the software does not perform unintended functions that jeopardize its safety requirements. 

The supplement introduces flie notion of model coverage analysis, analogous to structural coverage analysis. The purpose of model coverage analysis is to detect unintended functions in the model. 

Requirements should be traceable to design design should be traceable to code requirements, design and code should be traceable to tests. Traceabihty should be maintained when changes are made. There should also be traceabihty in the reverse direction, to ensure that no unintended functions have been created. 

Functional test including input partitioning, boundary values, unintended functions and nonspecified input values ... 

Unintended functions tested on critical paths and formal structured test management ... 

Systems are often designed with unintended functions that are not recognized. 

Functional verification of the models by using requirements based test vectors to ensure compliance of the models with the requirements and that no unintended functionality is implemented ... 

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