KWSys provides a platform-independent API to many common system features that are implemented differently on every platform. This library is intended to be shared among many projects. How to use KWSys from ITK: #include bool MyIsDirectory(const char* fname) { return itkkwsys::SystemTools::FileIsDirectory(fname); } How to modify KWSys: When adding a method to an existing class, make no mention of ITK. KWSys has no knowledge of ITK headers or libraries. Please also keep in mind that KWSys must be able to build on more platforms and compilers than ITK. Refer to existing code for conventions to ease this task. If you want to add a class, please contact the ITK mailing list for discussion. Please do not add a class without permission from Kitware.