This paper is concerned with the design and implementation of an integrated software package for the optimisation of general multipurpose batch and semi-continuous plants. In particular, we describe a sophisticated graphical user interface that supports the rapid specification of scheduling, planning, design and retrofit problems in an error-free manner. These problems are posed graphically and solved under a unified framework based on the state-task network process representation and a general characterisation of all production resources, such as processing and storage equipment, utilities and manpower. This representation facilitates the specification of processing recipes of arbitrary complexity, involving material recyles, shared intermediates, batch splitting and mixing and multiple routes to the same end-product. The architecture employed shields the users from the complex mathematical. models and solution procedures that are employed, freeing lip their time for problem specification and results analysis.