Content is verified to assure that it is within normal
specifications or to detect particular content.. Examples include
verification of parameter values on operating system calls, examination of
inbound shipments, and real-time detection of known attack patterns.
Complexity: In a limited function system, content checking is limited by the
ability to differentiate between correct and incorrect values within the
valid input range, while in systems with unlimited function, most of the key
things we commonly wish to verify about content are undecidable.