The ACIS checking functionality (or the Checker) is provided to help customers to detect bad or invalid data in their models. ACIS operations may not work on invalid models and operations on invalid models may become ill-defined.
The architecture for which the Checker is designed is that applications will read ACIS data from an outside source (for instance reading a SAT file), and then use the Checker to identify problems within that data. Any invalid entities that are detected should be either discarded or repaired. At the end of the checking process, the application should have a model that is free of any known defects, and ACIS operations can then be called with confidence.