A user (person) is permitted to act on an object if there is a path (series of permission Links) from the acting user to the object in which
-* Every intervening object is a Group, and
+* Every intervening object is a Group or a User, and
* Every intervening permission Link allows the current action
Each object has exactly one _owner_, which can be either a User or a Group.
Three lab members are working together on a project. All Specimens, Links, Jobs, etc. can be modified by any of the three lab members. _Other_ lab members, who are not working on this project, can view but not modify these objects.
-h3. 4. Segregated roles
+h3. 4. Group-level administrator
+
+The Ashton Lab administrator, Alison, manages user accounts within her lab. She can enable and disable accounts, and exercise any permission that her lab members have.
+
+George has read-only access to the same set of accounts. This lets him see things like user activity and resource usage reports, without worrying about accidentally messing up anyone's data.
+
+table(table table-bordered table-condensed).
+|Tail |Permission |Head |Effect|
+|Group: Ashton Lab Admin|can_manage |User: Lab Member 1 |Lab member 1 is in this administrative group|
+|Group: Ashton Lab Admin|can_manage |User: Lab Member 2 |Lab member 2 is in this administrative group|
+|Group: Ashton Lab Admin|can_manage |User: Lab Member 3 |Lab member 3 is in this administrative group|
+|Group: Ashton Lab Admin|can_manage |User: Alison |Alison is in this administrative group|
+|Group: Ashton Lab Admin|can_manage |User: George |George is in this administrative group|
+|Alison |can_manage |Group: Ashton Lab Admin |Alison can do everything the above lab members can do|
+|George |can_read |Group: Ashton Lab Admin |George can read everything the above lab members can read|
+
+h3. 5. Segregated roles
Granwyth, at the Hulatberi Lab, sets up a Factory Robot which uses a hosted Arvados site to do work for the Hulatberi Lab.