In CSI(C&F) only fuzzy variables must be declared before use. This seems to be convenient, as it combines the declaration of variable with the binding of a fuzzy variable to a certain ParameterSet-object. All other declarations are made implicitly by context. One exception is the EVALTREE object; in a first step you can create such an object explicitly by the contemporaneous definition of its structure. In a second step various evaluated FUYYZVAR objects can be inserted in this tree, but this is not the only way to create an EVALTREE. If you try to insert a FUZZYVAR object in an empty tree or in a not existent branch, a new tree or branch will be generated automatically. Nevertheless, CST(C&F) gives you a warning message in such a case.