Multi-Paradigm Programming through Graph Rewriting

Progress

Objectives:

There has been much research into programming languages and systems which
combine a number of programming paradigms, thus enabling different parts of
a system to be developed using the most appropriate model in each case.

Graph rewriting has been successful as a practical computational model for
functional programming and has application to concurrent and logic languages
as well. This project builds on this success for both sequential and
parallel implementations.

Progress:

The aim of the project is to investigate techniques for practical
implementation of multi-paradigm languages. However, the combination of
different paradigms must be performed carefully so that the combined system
has clear semantics.

On the practical front, the project has developed a model known as Object
Graph Rewriting (OGRe) which can be viewed as a system for rewriting a
collection of graph terms or as a simple process calculus. The model has a
natural concurrent implementation, but is also able to be implemented
efficiently on sequential machines.

Current experiments implement the language Facile, under development at
ECRC, Munich, using Standard ML to compile to C via OGRe. Facile combines
strict functional programming with explicit concurrency. Lazy functional
programming is also being investigated.

The theory of OGRe is being researched with emphasis on proving the
correctness of implementations based on the model. It has been necessary to
make a careful study of rewriting strategies in order to understand the
interaction between the paradigms represented by the various languages in
use. Foundational work on relative normalization has been performed with
Zurab Khasidashvili, Research Associate on the project.

Interim results from the project are available in the form of published
academic papers and in prototype sequential implementations.
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