The DIRAC interware is a complete Grid solution for one, or more than one community of users that need to exploit distributed heterogeneous resources.
DIRAC forms a layer between a community and various compute resources to allow optimized, transparent and reliable usage. The types of resources that DIRAC can handle include:
Computing Resources, including Grids, Clouds, HPCs and Batch systems
An alternative description of the DIRAC system can be found in this presentation