unified code generation interface for form-compilers

 UFC (Unified Form-assembly Code) is a unified framework for finite element
 assembly. More precisely, it defines a fixed interface for communicating low
 level routines (functions) for evaluating and assembling finite element
 variational forms. The UFC interface consists of a single header file ufc.h
 that specifies a C++ interface that must be implemented by code that complies
 with the UFC specification. Examples of form compilers that support the UFC
 interface are FFC and SyFi.