In a complex framework there are many ``domains'' where a tool must be available [Garl92]. In the case of an executable tool, it is desirable to have this tool available on the task level (i.e. in LISP in VISTA). Another case may be a C function in a library, which should be available to C, FORTRAN, and LISP applications. We say that C is the implementation domain and FORTRAN and LISP are the target domains of these functions or ``tools'' (in a general meaning, see [Hala94]). Since it is tedious and error-prone work to code language bindings from the implementation to the target domains manually, the TAC (Tool Abstraction Concept) was created, which uses an abstract description of a tool or function encoded in the implementation domain (i.e. a formal comment describing a C function, its arguments and its return value) from which language bindings to the target domains can be created automatically.