**3.3.3 VOMS**

VOMS [41] stands for Virtual Organization Management Service and is one of the most commonly used Grid technologies needed to provide user access to Grid resources. It works with users that have valid Grid certificates and represents a set of tools to assist authorization of users based on their affiliation. It serves as a central repository for user authorization information, providing support for sorting users into a general group hierarchy - users are grouped as members of Virtual Organizations (VOs). It also keeps track of users' roles and provides interfaces for administrators to manage the users. It was originally developed for the EU DataGrid project.
