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Groups are simply lists of EPerson objects. Other than membership, Group objects have only one other attribute: a name. Group names must be unique, so (for groups associated with workflows) we have adopted naming conventions where the role of the group is its name, such as COLLECTION_100_ADD. Groups add and remove EPerson objects with addMember() and removeMember() methods. One important thing to know about groups is that they store their membership in memory until the update() method is called - so when modifying a group's membership don't forget to invoke update() or your changes will be lost! Since group membership is used heavily by the authorization system a fast isMember() method is also provided.

Two specific groups are created when DSpace is installed:  Administrator (which can bypass authorization) and Anonymous (which is assigned to all sessions that are not logged in).  The code expects these groups to exist.  They cannot be renamed or deleted.

Another kind of Group is also implemented in DSpace‚ special Groups. The Context object for each session carries around a List of Group IDs that the user is also a member of‚ currently the MITUser Group ID is added to the list of a user's special groups if certain IP address or certificate criteria are met.

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