NOAH: A CSP-based language for describing the behaviour of coupled models

• Published in: Software, practice & experience Vol. 38; no. 2; pp. 135 - 159
• Main Authors: Armstrong, C. W., Ford, R. W., Freeman, T. L., Riley, G. D.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01-02-2008
• Subjects: automatic code generation; coupled modelling; CSP; deadlock; FCA
• ISSN: 0038-0644; 1097-024X
• DOI: 10.1002/spe.822

Scientists in many fields rely on computational simulations that are built from a collection of separate, inter‐communicating single models (e.g. Earth System Models often consist of single models of the ocean, atmosphere and land processes); these simulations are called coupled models. Coupled models allow scientists to simulate richer scientific phenomena than is possible by running single models alone. Scientific interest is typically focused on the investigation served by a coupled model, rather than the complex and inadequately supported software engineering activity of constructing it. In response to this lack of support, a coupling methodology called the Flexible Coupling Approach (FCA) has been developed at the University of Manchester together with a tool that implements this approach, the Bespoke Framework Generator (BFG). Whilst being adequate for a large class of coupled models (e.g., many Earth System Models), the BFG is unable to handle coupled models with complex behavioural requirements (in terms of the scheduling and inter‐communication of single models). To capture these more complex expressions of behaviour, this paper introduces NOAH, a domain‐specific language that is implemented in the formalism Communicating Sequential Processes (CSP), and which is used by a new implementation of the FCA, called the CSP‐based Framework Generator (CFG). NOAH is introduced through two example coupled models which have complex behavioural requirements. NOAH represents the first attempt to bring the advantages of using formal descriptions of coupled models to application scientists, providing a language in which to specify coupled model behaviour precisely and the ability to check that a coupled model is deadlock free using tools such as the Failures‐Divergence Refinement (FDR) model checker. Copyright © 2007 John Wiley & Sons, Ltd.