I experiented copyright management which is a great extension, but has some weakness. I would like to propose more general system that would:

• make the difference between the creator and the holder of the licence. Generally, the holder is different - it can be a group of persons, an institution, etc. It can be naturally the creator, if he is unique, but generally he is not!
• let the first author of the page choose the licence, this way, next authors cannot modify the licence of the work already done, but they can be informed of the use of their contribution to the page,
• consider evry user contributing to the page as _co-creators_, using tiki history to list them.
• let the author the freedom not to chose any licence if he wants to!

It is a texte attached to the licenced work with:

• a holder, it's a name,
• a date, it's the date of the creation of the page,
• general conditions, it's just a text,
• special conditions that explain how general conditions are used.

General conditions are made by layers, and taken as they are.

it's inspired of Creative Common work on copyright. The first author makes choices on the licence. These choices are viewed as a list of assertions.

• Assertion is a verb and a predicate. The verb is one of those: "permits" , "requires" , "prohibits" and the predicate for example one of those: "Reproduction" , "Distribution" , "Notice" , "Attribution" , "CommercialUse". But the list of predicates depends on the general conditions.
• extend the use of licence to other objects of the tiki (wiki pages, articles),
• produce an RDF form of the licence imbedded in the html (very simple),
• simply remember, on a short and small text the terms of the licence at the botton of printed pages, giving the url of the texts and their titles. We can consider these url secure enough not to be modified.

There are different tables:

• licence_instance they have a unique name, and contain general informations of the licence. A work can be linked to one of those. This table does not contain the creators list,
• licence_instance_assertions a list of assertions for each licence_instance,
• licence_objects a list of available licences in which the author can chose.

The first and second table could also be in one table.

It's the most important. Tiki has to garanty to is users that the licence they use is kept in a secure place, and kept linked to their work.
What could compromise such a system:

• the deletion of the licence that would break the link between the work and the licence,
• the edition of the licence that could change the terms on which the authors agree,
• the edition of the link between the work and the licence.