Middleware

Although WLCG depends on the underlying Internet – computer and communications networks – it is novel software that enables the user to access computers distributed over the network.

This software is called 'middleware' because it sits between the operating systems software of the computers and the physics applications software that solves a particular problem. It is a series of cooperating programs, protocols and agents designed to help users access the resources of a grid.

Middleware is essential for WLCG to work – without it WLCG would not exist.

The most important grid middleware stacks in WLCG are:

• EMI (European Middleware Initiative), combining the key middleware providers of ARC, gLite, UNICORE and dCache
• Virtual Data Toolkit
• Globus Toolkit developed by the Globus Alliance