Section: New Results
Advanced programming models for the Grid
In our past work, we developed the -calculus and HOCL , a Higher-Order Chemical Language based on the -calculus. HOCL has been used to express workflow enactment and autonomic systems. This was the subject of Yann Radenac's PhD thesis, defended and published in April 2007  .
In 2008, we have investigated how to use HOCL to express dynamicity in scientific workflow. This is a joint research activity between SZTAKI (Hungary) and University of Vigo (Spain) that is being carried out within the CoreGRID network of Excellence. Dynamicity is a recurrent topic in traditional workflow systems. The need and feasibility to perform changes in workflow process instances while they are being executed has been a main (and to a long extend yet unsolved) challenge. We first analyzed dynamicity scenarios and requirements in scientific workflows. This work led to the publication of a CoreGRID technical report  within which we identified five general scenarios involving different dynamicity needs and illustrated byt concrete examples. These scenarios were used to identify a set of dynamicity requirements for scientific workflows support. After this initial phase, we introduced a proposal for a scientific workflow execution system based on HOCL. This proposal led to several publications  ,  .
We also studied how to express service orchestration using the Chemical Metaphor. We have shown in  that chemical programming can be a good candidate for service programming, such as the composition and coordination of services.
A collaboration has been set up with ICT (China) under the framework of the UNCONV INRIA associated team and the FP6 IST EchoGRID project. We studied how HOCL can give a formal semantics to GSML (Grid Service Markup Language). GSML is a programming language that has been designed at ICT for grid end-users to overcome the programming hurdle and the high learning curve associated with Grid infrastructures that are complex distributed computing systems. This work led to a joint publication  . This paper describes the translation of GSML programs into HOCL allowing to give a precise definition of the concepts of GSML, especially sessions. The semantics also bridges the GSML and chemical computing paradigms. Another topics is being investigating to design an autonomic map&reduce framework for the execution of parallel applications over a Desktop Grid.
Finally, we started a collaboration with STFC (UK) under the framework of the CoreGRID Network of Excellence to study security engineering of distributed systems, such as Grids, when following the chemical-programming paradigm. We have analysed in  , how to model secure systems using HOCL. Emphasis is on modularity, hence we advocate for the use of aspect-oriented techniques, where security is seen as a cross-cutting concern impacting the whole system. We show how HOCL can be used to model Virtual Organisations (VOs), exemplified by a VO system for the generation of digital products. We also develop security patterns for HOCL, including patterns for security properties such as authorisation, integrity and secure logs.