[Odrl-version2] Handling Prohibitions

[Alapan Arnab]

Hi,
After rethinking on the issues discussed recently, I am wondering if
there there is a need for prohibitions in the first place?

The permissions in a license come from a finite set defined in a data
dictionary. Ideally, the DRM controller should only enforce the
permissions defined by their respective permission sets. Thus take a
random permission, p, and a permission set PS. There can be four
possibilities.

p is an element of PS, and appears in the license: In this case, the
permission is granted to the assignee

p is an element of PS, and does not appear in the license: In this case,
the permission is not granted to the assignee

p is not an element of PS, and does not appear in the license: In this
case, the DRM controller has no say on whether the permission is allowed
or not.

p is not an element of PS, and appears in the license: This creates an
invalid license as the license is using terms that do not exist.

If we look at the permissions in a license in this way, I do not see why
a prohibition is necessary. Even a "all rights but" statement, is purely
a contraction, and as Vicky suggested a tool to convert from a "all
rights but" to a proper rights statement is a better approach.

The one issue that remains is off course a change in permission sets -
specifically if the permission set changes without a change in the
namespace of the permission set. Changing namespaces once published
should be discouraged, but I do not see a technical solution to this
problem.

Regards,
Alapan
On Tue, 2006-01-31 at 18:42 -0500, Vicky Weissman wrote:
> Hi All,
> 
> I've looked over the email discussions are prohibitions and, based on them, I
> suggest we do the following:
> 
> (1) Extend agreements to include prohibitions, where a prohibition says that
> an action is forbidden if certain conditions hold.
> 
> (2) Extend agreements to include a default, which is either permit or forbid.
> 
> (3) Say that a set of agreements imply that a request (e.g., may Alice
> download Season 1 of Lost) should be granted if (a) the agreements together
> imply the request should be granted or (2) the agreements together do not
> imply the request should be granted, do not imply the request should be
> denied, and the default for all agreements is permit.
> 
> Are there any objections?
> 
> -Vicky  
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-- 
Alapan Arnab
Data Networks Architecture (DNA) Laboratory
Department of Computer Science
University of Cape Town
Rondebosch, 7700
South Africa

Tel: +27 21 650 3127
Web: http://people.cs.uct.ac.za/~aarnab/
Blog: http://idiots-mind.blogspot.com
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