The implementation of nonlocal dependency relationship in interactive environment

The attribute grammar is a convenient tool for specifying the semantics of programming languages. It has been used widely in the development of interactive programming environments. To date, many environments are constructed based on attribute evaluation. However, in traditional attribute grammar, a lot of copy rule chains must be used due to its essential limitations, which results in severe time and space problems. To improve the efficiency, the attribute grammar is extended by allowing a nonlocal dependency relationship (NDR). The use of this NDR avoids semantic information flowing through copy rule chains. The representation of NDR is described. An approach to maintaining the consistency of NDR in the semantic tree during program development is presented. The implementation of the NDR is discussed