This project continues NSF previously funded research in Distributed Language-based Environments. The objective of this project is to develop a formal model, underlying algorithms and proof-of-concept implementation of change propagation, which is modelled as parallel and distributed incremental evaluation of an attribute grammar defining centralized or decentralized attributed parse trees in response to multiple asynchronous subtree replacements on a tree. In this project, algorithms for several aspects of such change propagation will be investigated, including support for multiple agents initiating subtree replacements, maintenance of underlying data structures, and coordination of evaluation processes, with particular consideration to tradeoffs between attribute evaluation and bookkeeping costs. The initial application is to multi-user distributed language-based programming environments, where programmers employ workstations connected by a local area network and modify segments (modules) in a decentralized attributed parse tree (program).
