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Re: PROV-ISSUE-64 (definition-use): definition of use [Conceptual Model]

From: Simon Miles <simon.miles@kcl.ac.uk>
Date: Fri, 9 Sep 2011 14:59:03 +0100
Message-ID: <CAKc1nHcjvak37KJaP2YtXg=qw6TNFy7DxepQO9xe0PV_L1-9Mg@mail.gmail.com>
To: Provenance Working Group WG <public-prov-wg@w3.org>
Hi Luc,

> I may not have been clear. I think that the requirement of roles to
> define derivation is a stronger justification than data structure
> uniformity.

OK. I think this raises three sub-issues: (i) that is not the
justification for mandatory roles currently given in the text; (ii)
the use of roles in derivation assertions sounds like role types
rather than role names, i.e. there appears to be no necessity for the
roles mentioned to be unique; (iii) roles are optional in derivation
assertions, so it seems odd that this be a rationale for them being
mandatory in other assertions.

> You still seem not to take into account the optional nature of asserting
> roles. Maybe, it's a question of presentation in the document.  But
> ultimately, we are
> telling people you are free not to express roles. Under the bonnet, there
> will be an unspecified role. I don't understand what the problem is with
> this approach, where a default value is provided.

My problem with this approach is that I am unclear what "under the
bonnet" really means. I also agree with Graham's point that, whatever
it is, I don't know whether we should be standardising it.

Regardless of any of the above, I still think the opaqueness of "Roles
are mandatory since they allow for uniform data structures" is the
most pressing issue. I think it answers a necessary question (why
mandatory?) but in an unhelpful way.

Thanks,
Simon


On 5 September 2011 10:20, Graham Klyne <GK@ninebynine.org> wrote:
> On 05/09/2011 08:17, Luc Moreau wrote:
>> You still seem not to take into account the optional nature of asserting
>> roles. Maybe, it's a question of presentation in the document. But ultimately,
>> we are
>> telling people you are free not to express roles. Under the bonnet, there
>> will be an unspecified role. I don't understand what the problem is with
>> this approach, where a default value is provided.
>
> I think there may be a mismatch here between designing a *system* and defining a
> *standard* - the point of a standard is to specify what is visibly exchanged
> between systems.
>
> In particular, if the role is optional, then it is unhelpful to say "Under the
> bonnet, there will be an unspecified role", because what exists "under the
> bonnet" is exactly an implementation choice.  If I write a system that uses
> provenance information in a limited fashion that never involves roles (which is
> OK, as you have said they are optional), then there is no unspecified role under
> the bonnet.
>
> Thus, if the presence of a role is optional in the exchange of provenance
> information, then I think it should be optional in the model, as it is the
> exchangeable provenance information that we need to model here.  Maybe, as you
> say, this is simply a matter of choosing appropriate phrasing.
>
> #g
> --
>
>



-- 
Dr Simon Miles
Lecturer, Department of Informatics
Kings College London, WC2R 2LS, UK
+44 (0)20 7848 1166
Received on Friday, 9 September 2011 13:59:35 GMT

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