[Odrl-version2] Constraints on duties - I think I've got it now...

[Vicky Weissman]

Hi,

If I understood your last mail correctly, the agreement 

Party=Alice
Perm=Download
Asset=F
Duty=d
Duty.Constraint=c
Duty.Relax = false

means that Alice may download F if she has (1) fulfilled duty d at time t and
(2) at time t, constraint c holds.  So, if d = "pay 5 Euros" and c is "time
is before June 30, 2006", then Alice may download F if she has already paid 5
euros and that payment was made before June 30, 2006.    

Assuming this correct, lets see how the definition plays out in a few other
examples.

Party=Alice
Perm= lock
Asset= f.src
Duty= unLock
Duty.Constraint= within 24 hours
Duty.Relax = true

This means that Alice is allowed to lock the source file f.src, and she can
keep the lock for as long as she wants.  However the agreement writer/owner
asks that she release the lock within 24 hours of taking it (i.e., she ought
to - but is not legally required to - unlock within 24 hrs.)  Note: I'm
assuming Duties do not have to be payments (as clarified by Susanne) and the
application-specific vocabulary includes the constant
"time_Alice_Last_Locked_f.src", so we can have a constraint "before
time_Alice_Last_Locked_f.src + 24 hrs".  

I wonder if duties should have (optional) consequences.  For example, maybe
the agreement owner would like to say "Alice may lock f.src; she should
return the lock within 24 hours, and, if she doesn't return the lock, then
she'll be charged one Euro a day".  More generally, relaxed duties allow
obligations to hold after the right has been granted/exercised, so I think
it'd make sense (and is often the case in practice) for there to be
consequences to unmet obligations.  What do you think?  

-----

Party=Alice, Bob
Perm= download 
Asset= F
Duty= pays 1 euro
Duty.Constraint= user is over 21
Duty.Relax = false

This means (1) if Alice is over 21, then she may pay 1 euro and, if she pays
the euro, then she may download F.  The same is true for Bob.  So the
agreement is equivalent to one that says "Alice/Bob may download F if she/he
is over 21 and pays a euro".  That is, the agreement is equivalent to

Party=Alice, Bob
Perm= download 
Asset= F
Duty= pays 1 euro
Perm.Constraint= user is over 21
Duty.Relax = false

----
(This one's really about parties v. individuals.)

Party=Alice 
Perm= download 
Asset= F
Duty= pays 1 euro
Duty.Assignee = {Alice, Bob}
Duty.Beneficiary = {Charlie, Dan}
Duty.Relax = false

The agreement says that Alice may download F if {Alice, Bob} has paid 1 euro
to {Charlie, Dan}.  Suppose Bob gives a euro to Charlie.  Then does it
necessarily follow that {Alice, Bob} has given a euro to {Charlie, Dan} and,
thus, Alice may download F?  

Thank you so much for your patience.

Best,
Vicky