Review of the Evaluator Truth Tables of 5 September

Hi all,

I have reviewed the draft Truth Tables of the Evaluator at
https://www.w3.org/2016/poe/wiki/Evaluator as of 5 September.

Find my comments at https://github.com/w3c/poe/issues/254

(for a quick and easy use copied and pasted below)

 

Best,

Michael

 

=========== copy of the Github issue 254

 

This is a review of the Truth Tables of an ODRL Evaluator as shown in
<https://www.w3.org/2016/poe/wiki/Evaluator>
https://www.w3.org/2016/poe/wiki/Evaluator - version of 5 September:

What is stated exactly by Not-/Active - see
<https://github.com/w3c/poe/issues/245> #245 - has not been clarified yet,
my assumption from how it is used in the Truth Tables:

*	Active = can be used for further evaluation or other ODRL processing
*	Not-Active = cannot be used ...

For the three sub-classes of Rule this translates into

*	Permission: if Active the action of the Permission may be exercised
*	Prohibition: I can't draw a direct conclusion because of the very
few Prohibitions in the examples. See comment on example 24
*	Duty: the state Active is required as prerequisite for stating a
Duty has been Not-/Fulfilled, this depends on taking the action of the Duty.
By that three states of Duty have to be considered by a Rule referring to
it: Fulfilled, Not-Fulfilled, Not-Active

I comment only on Truth Tables I have a different view on - not-commented
tables are ok.

*	Example 16 + 17: why does the Evaluator evaluate the target and the
assignee? This is not done for any other example. And the shown conclusion
is not easy to follow: to be able to evaluate the state Not-/Satisfied of
the refinement in example 17 it is required to have a real entity to be
matched against this refinement and this requires to match the entity first
against the PartyCollection. (Similar issue with example 16) A Truth Table
about such examples needs to include the state of a "is the entity a member
of the Collection" evaluation.
*	Example 20: An Obligation is an instance of a Duty Class and the
full evaluation state of a Duty is: Not-/Fulfilled. The shown Truth Table
does not take the action into account. But this should be done by the Duty
Class specification:  <https://w3c.github.io/poe/model/#duty>
https://w3c.github.io/poe/model/#duty
*	Example 21: columns with a blank header need one defining what the
state in the rows below is about.
The second column shows Not/Fulfilled states. It looks like the state of the
Obligation as Duty without taking the consequence into account. Conclusion:
if an Obligation (=Duty) is Not-Fulfilled (= the action has not been
exercised) after this first round of evaluation a second round is entered to
evaluate the consequence too.
And: where is the final state of the Obligation - after having taken into
account consequences, if required?

*	the 1st row shows Cq1=Not Active: by what evaluation has the
consequence been de-activated? But: having exercised the action of a Duty
does not require to evaluate any existing consequences, therefore the Cq1
value is not relevant for the evaluation of the Obligation/Duty.
*	The 3rd row shows that Cq1 is Active despite of a Not-Satisfied
refinement R1 - this is wrong.
*	The 4th and the 5th row show if fact the same as row 1 - but now the
refinement is taken into account. As said above: if the action of a Duty has
been exercised - and this is reflected by the Fulfilled state in the 2nd
column - consequences don't need to be evaluated. Therefore these two rows
are misleading. (In fact the final state of Obligation must be Fulfilled for
both rows.)

*	Example 22: (only match the JSON-LD in the IM with the Truth Tables
- regardless of issues with the semantics)
This example shows related/referenced Rules: the Permission Rule references
a Duty Rule by a duty property. The rule for evaluating constraints and
refinements of a Rule is therefore: this evaluation needs to be done
independently for the constraints of the Permission and the refinements of
its action AND for the constraints of the Duty and the refinements of its
action!
Conclusion: C1 and R1 have a direct impact on D1 only, and only the state of
D1 has an impact on P1
Going over the Truth Tables - guessing the column with the blank header is
the state of D1

*	row 1 + 2: ok
*	row 3: if R1 is Not-Satisfied, Duty D1 cannot be Active.
*	row 4: C1 is shown as Not-Satisfied. Why does R1 show no state?
Because of the Rule "if any consequence or refinement is Not-Satisfied the
consequence+remedy evaluation results in Not-Satisfied"? The other cells of
the row are ok.

*	Example 23: re the columns with blank headers: see Example 21
comments above.

*	row 2: why is P1 not Active, the duty has been finally fulfilled by
Fulfill-ing the consequence
*	row 4: why does it show states for Cq1 and the next column as Cq1 is
not relevant, the action of the Duty has been exercised.
*	row 5: if the action of a Duty has been exercised it is not required
to fulfill a consequence - a Not-Fulfilled consequence cannot set a
Permission to Not-Active in this case.

*	Example 24: a Truth Table has to include if the action of a
Prohibition has been exercised or not as this is the trigger of the
relevance of a remedy.

*	row 3: why does exercising the disallowed action and then fulfilling
the remedy set the Prohibition to Not-Active? It must be the same state as
"the disallowed action has not been exercised" - but this state is not shown
in the Tables and the semantics of "a Prohibition is Active" (or ...
Not-Active) are not defined.

*	Example 25: the headings show an issue: at first sight C1 and C2 are
constraints side by side, but they aren't: C2 is a constraint on the Duty
and not on the Permission. Suggestion: use "D1.C2" and "D1.R1".

*	row 3 + 7: R1 of D1 is Not-Satisfied, therefore D1 must be
Not-Active