The Open Group Single UNIX Specification
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This FAQ is to help explain the visibility levels in a Plato web.

What are visibility levels?
Visibility levels allow a single Plato web to be viewed by different groups of people, who can see differing subsets of the items on that web. They are conceptually a hierarchic set of layers. They can also be thought of as access levels.
How many visibility levels are there?
There are a maximum of 4 visibility levels: a public level and 3 protected levels for which a username and password is required for authentication and hence the appropriate entitlements. There must be at least one protected level, in order to be able to create items on the web. Protected levels have access control determined by membership of a Sophocles access control list.
How do I reference these levels?
The levels are numbered 40 (public), 30, 20 and 10 respectively. Level 10 has the most privilege. By default they are named "Public", "All member", "Forum", "Working Group", but these tags can be changed.
What can each level do?
The public level has read-only access. The others may have read and write access - but by default only level 10 has this facility. When items such as documents are created they are given a visibility level. All users at that level (or less) can see these items. For instance, a document created at "All member" level (30) can be seen by levels 30, 20 and 10, but not 40 - the public level. Similarly an event created at level 10 can be seen only by that level.
How are visibility levels defined?
The Plato web designer first identifies if a public level is needed and then how many protected levels. For each protected level one or more Sophocles access lists are identified, membership of any of which entitles access at that level. Within Sophocles an access list used for Plato access control has to be defined as for use both for Email and Web.
How does a user view a particular level ?
When a user logins in to gain access to a protected level, the system evaluates the lowest level they may access and automatically sets this as their view of the site.

This is the maximum number of levels :

Level number Generic name  
40 PUBLIC  
30 ALL MEMBERS Authentication required
20 FORUM
10 WORKING GROUP

This is the minimum number of levels :

Level number Generic name
10 WORKING GROUP

Further information on Plato including troubleshooting tips is available here

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