ISIM’s main product is the Dynamic System Simulation tool ESL. ESL was born out of a research contract undertaken in 1980/81 by the University of Salford, UK for the European Space Agency (ESA) to evaluate simulation algorithms for parallel computer architectures.

One outcome the this research project was a proposal for a new standard for Continuous System Simulation Languages (CSSL 81) which incorporated, amongst other innovations, special features to allow the use of multiple parallel processors to simulate physical systems (the ESL segment structures).

Other features of the new standard included a hierarchical model – submodel structure; the concept of an experiment region and a mechanism for specifying and accurately detecting discontinuities.

There followed a series of contracts with ESTEC at Noordwijk (ESA’s technical division) to implement the proposed standard and the ESL Simulation Language was created.

Since that time, the underlying simulation language has remained largely unchanged but today’s modern product with its graphical user interface (ESL-Studio) and many features has evolved.