Extended Relations + Constraints On Constraints proposal

Dear WG, I have a proposal to address the two main outstanding requirements; 
 - Extended Relations [1]
 - Constraints on Constraints [2]

Since we have updated the constraint model with clearer left/right operands - and the constraint model itself naturally supports comparison operations, then I recommend we only support Extended Relations for Constraints. In this case, each left and right operand would be two constraint objects, and the operators odrl:xor odrl:or odrl:and can be used to express the relation. (note: we don’t need odrl:and as that is the default, but we can add it anyway for completeness.)
(See the last example at [1] for a sample.)

In a very similar fashion, to support “constraints on constraints” all we need to do is define a new operator that (semantically) indicates that one constraint “is dependent” on the other. Lets say, for example, that is called “odrl:dependsOn”.
so, “c1 odrl:dependsOn c2” would mean that the first c1 constraint would have to be satisfied first, then the second c2 must then be satisfied.

In our classic example “30 mins after the football” match, c1 would be the football event ending, and c2 would be wait 30 min period.
(Note: this is not the same as odrl:and as that means I can wait 30 mins at the same time wait for the game to end.)

This proposal has no change on the model, and only the addition of the operators to the vocabulary.

Thoughts…

Renato Iannella, Monegraph
Co-Chair, W3C Permissions & Obligations Expression (POE) Working Group

[1] https://github.com/w3c/poe/issues/63 <https://github.com/w3c/poe/issues/63>
[2] https://github.com/w3c/poe/issues/62 <https://github.com/w3c/poe/issues/62>