[Odrl-version2] RE: ODRL-Version2 Digest, Vol 6, Issue 5

[Vicky Weissman]

Hi,

I can't answer most of Steve's questions/comments, but I have a few
responses.

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Vicky wrote:

3**)  It seems to me that there are two types of Rights entity, an agreement
and a request...<snip>...If this is correct, then wouldn't it be simpler and
clearer to remove all but the agreement and request 
entities and to say that partial agreements can be created to suit an
application's needs....>>

Steven replied:

Perhaps, but if ODRL is going to standardize the DRM process so that all user
agents can understand it, then this would require a fairly subtle (and likely
complex) layer of constraints on how the agreemtents could be rewritten,
would it not? ...<snip>

Vicky's reply:

Maybe I'm being naïve, but I think all we need is a constant `unspecified',
which can appear anywhere in an agreement.  The assigner of the agreement is
allowed to replace any occurrence of `unspecified' with anything else and the
assignment is complete (i.e., can be used to imply a permission) if and only
if none of the fields in the assignment are `unspecified'.  Why would things
need to be more complicated than that?  

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>2.2 Asset Model

Vicky wrote:

In particular, suppose that an agreement gives Alice the right to copy a
speech that has 5 parts.  Why should it necessarily follow that Alice may
copy only one of the parts, possibly taking it out of context?

Steven replied:
Would this not already be convered by Constraint/Prohibition in the
Agreement? In other words, the Agreement will be specifically set up by the
Assignor so that this can't happen.

Vicky replies:
I think you're suggesting that an agreement include a permission and a
prohibition, where the permission says that the speech may be copied, which
implies that each part may be copied, and the prohibition says that none of
the parts individually may be copied.  This raises an interesting question,
namely how do we interpret an agreement (or set of agreements) that
contradicts itself.  More generally, how do we determine what's
allowed/forbidden by a set of agreements?  I asked this in my last email and
suspect that the answer will tell us if the assumption can be worked around
in the way that you suggest.

I'm not sure how we can use constraints to work around the assumption.  (I'm
not saying we can't, I'm just saying I don't see how we can.)  

+++++++++

Vicky wrote:

4) Suppose that an agreement includes a permission whose Action is {`copy',
`download'} and the exclusive Boolean flag is set. ...<snip>...I think I'm
missing the intuition behind the flag.

Steve replied:
<snip>...I think [the meaning of the exclusive Boolean flag] is "one or the
other but not both", which doesn't seem so hard...<snip>

Vicky replies:
My best guess is that the exclusive flag is used in agreements as a way to
promise the assignee(s) that no one else is getting permission.  For example,
consider an agreement in which Pixar gives Disney the right to distribute its
latest movie.  If the `exclusive' flag is set in the agreement, then Pixar is
not only giving Disney the distribution right, Pixar is also promising Disney
that it won't give the right to anyone else.  

Of course, that's just a guess.  It might be the case, as Steven suggests,
that the flag is an xor.  But then it's not clear why the xor is linked to
actions.  In fact, it's not clear why you'd want xor at all.  Suppose that,
if a customer can't play a movie, then she can either request a refund or
asked for another copy of the film (but not both).  This seems like a
reasonable statement for a movie vendor to make and it does involve an xor.
But I think we could capture the statement without xor as a set of statements
including `if a customer can't play a movie and she hasn't requested another
copy, then she may ask for a refund'; `if a customer can't play a movie and
hasn't requested a refund, then she may ask for another copy'; and `if a
customer can't play a movie then she is forbidden to do the action of
requesting another copy while simultaneously asking for a refund'.  More
generally, I suspect we can capture the statements that use xor in practice
with ones that don't.  BTW: could we capture the example in ODRL?  Off the
top of my head, I don't see how because each agreement mentions only one
asset.    

Best,
Vicky