[Odrl-version2] RE: ODRL-Version2 Digest, Vol 12, Issue 4

[Vicky Weissman]

<Alapan Arnab>
A ticket in both models is essentially the same as a ticket for a concert,
the bus etc - it gives the bearer a set of rights from the rights holder; and
the bearer is not a defined party (so I could give you my ticket and you will
have access).

<Vicky Weissman>
If that's the case, then a ticket is a contract in which the relevant party
is "agreement holder", so I still don't see why ODRL has both
agreements/contracts and tickets, rather than a principal "agreement holder"
(which I think would be simpler).

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<Vicky Weissman>
I'm not sure why a use license cannot both grant some permissions and forbid
others.

<Alapan Arnab>
My problems with the existing model was the fact that it was possible to have
a license that granted and forbid the same set of permissions. This problem
is clearly overcome with my approach.

<Vicky Weissman>
Whether your approach overcomes the problem depends on how we reason about a
set of licenses.  If we consider each license independently of the others,
then I agree that your approach solves the problem.  If we consider the
licenses as a set, then the problem essentially still exists, since one
license can permit an action that another forbids.    

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<Alapan Arnab>
The current motto in RELs is - grant only the rights that are mentioned.
Thus in a prohibition model - it should simply be assign all the rights
except the ones mentioned. For this reason, there is no need to ever express
a set of rights that are forbidden.

<Vicky Weissman>
If we assume every action that is not explicitly permitted is forbidden, then
we lose the distinction between what is forbidden and what is unregulated
(i.e., we force every agreement to regulate every action).  As a result,
agreements will often contradict one another, even when the intentions of the
agreements' writers are not in conflict. 

To illustrate the idea, suppose that Alice's mother says she may have a
cookie (i.e., issues an agreement giving Alice this right) and Alice's father
says she may play outside (i.e., issues an agreement giving Alice this
right).  If I've understood your suggestion correctly, then you would say
that Alice's mother permits Alice to have a cookie and forbids Alice from
doing anything else, including playing outside and even breathing; similarly,
Alice's father permits Alice to play outside and forbids Alice to do anything
else, including eating a cookie and breathing. So, while the parents agree
that Alice is not allowed to breath, they disagree over whether she may eat a
cookie and whether she may play outside.  That is, the agreement issued by
Alice's mother contradicts the agreement issued by Alice's father (and the
overall interpretation is just plain silly).  

It is not clear how we could "fix" the agreements.  Certainly, the agreements
could be rewritten so that Alice's mother and father both permit eating a
cookie, playing outside, and breathing (along with all other unobjectionable
activities).  But what if Alice's mother doesn't care about whether Alice may
play outside?  Then we're forcing the mother to regulate an action that she
doesn't care about and, if she permits when the father forbids (or
vice-versa), we get a conflict.    

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<Vicky Weissman>  
suppose an agreement says only that Alice may print 5 copies of the report.
Your suggestion could be equivalent to "if Alice has not made 5 copies, then
she may print the report and is forbidden to do anything else; otherwise, she
is forbidden to do any action".  Alternatively, you could mean "if Alice has
not made 5 copies, then she may print the report and she is forbidden to do
anything else to the report; otherwise, there is no action that she can do
legitimately that involves the report".  

<Alapan Arnab>
On the examples you mention (with Alice printing) - I am not sure what the
difference is.

<Vicky Weissman>
The first interpretation implies that Alice is forbidden to breath; the
second implies only that she is forbidden to breath on the report (or do
anything else *to the report*, other than possibly printing). 
 
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<Alapan Arnab> 
I would like to read your journal paper. 

<Vicky Weissman> <grinning>
The current version can be downloaded from
http://www.cs.cornell.edu/People/vickyw/tmp/PucellaWeissman.pdf (.ps).
Comments very welcome (though, for reasons of personal sanity, I probably
won't put in changes until the paper has come back from review).  

Best,
Vicky