Today’s computing environments are anything but static. Hardware is constantly being replaced and newer machines typically require recent operating systems and/or versions.

WLCG needs tools that go beyond what is commercially available to satisfy the dynamically changing demands of the HEP community. We depend upon many other grid projects for the supply of much of the specialized software used to manage data distribution and access, as well as job submission and user authentication and authorization, and software known collectively as the Grid middleware.

The four main component layers to WLCG are: