[Odrl-version2] Duties query

[Francis Cave]

David Martin and I have been discussing different kinds of duties, and we
believe that there is a need to make a distinction between on the one hand a
duty to perform an action once, thereby making a permanent change to the
status of the party performing the duty, and on the other hand a duty to
perform an action every that the permitted action is performed.

 

Consider, for example, a duty to make a payment. It could be that the
payment only has to be made once after which the permitted action may be
repeated any number of times, or once for every time the permitted action is
to be repeated.

 

I presume that this distinction can be made by using a Constraint. Would the
following be reasonable?

 


a) If the duty must be performed every time (no Constraint needed?)

 

<o:permission>

                <o:asset uid="."/>

                <o:action name="o:play"/>

<o:duty>

                <o:asset uid="."/> {how much to pay}

                                <o:action name="o:pay"/>

                                <o:constraint name="o:dateTime"
operator="o:lt" rightOperand="x:actionDateTime"/> {when to pay: before EACH
use}

</o:duty>

                <o:role function="o:assignee" uid="."/>

<o:permission>

 

b) If the duty must be performed once before the permitted action is
performed for the first time (Constraint needed).

 

<o:permission>

                <o:asset uid="."/>

                <o:action name="o:play"/>

<o:duty>

                <o:asset uid="."/> {how much to pay}

                                <o:action name="o:pay"/>

                                <o:constraint name="o:count" operator="o:eq"
rightOperand="1"/> {number of times to pay = once}

                                <o:constraint name="o:dateTime"
operator="o:lt" rightOperand="x:actionFirstPerformedDateTime"/> {when to
pay: before FIRST use}

</o:duty>

                <o:role function="o:assignee" uid="."/>

<o:permission>

 

The second of these expressions seems to make sense, but I'm not sure about
the first. Does that also need a constraint on the number of payments?

 

Am I missing something obvious?

 

Francis

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