- From: Simon Miles <simon.miles@kcl.ac.uk>
- Date: Wed, 31 Aug 2011 15:05:03 +0100
- To: Provenance Working Group WG <public-prov-wg@w3.org>
Luc, I've reopened this issue (and closed issue 66). I don't have an answer to the issue, but I can try to help by breaking down my concerns. 1. Part of the lack of clarity seems to be about the reason for mandating role names. Putting myself in the shoes of a general user, I would interpret something being declared mandatory as meaning it was necessary to be included otherwise something critical (e.g. reasoning on provenance) would not work. However, the argument below seems to be that PIDM expresses assertions by fixed-length tuples ['tuple' might not be quite the right term], so no element of that tuple can be excluded, and so every piece of data mentioned in every definition is mandatory. 2. The statement, "Roles are mandatory since they allow for uniform data structures.", which might clarify point 1, is itself not clear. "Data structures" are mentioned nowhere else in the model document, so it is not clear we mean the assertion tuples. And if we are to say that uniformity is critical, we have to say to who and/or why. Uniformly including role names is not obviously important to those wishing to assert what has occurred or to those querying provenance, except in the case where they want to replay executions. 3. There seems an underlying assumption that the conceptual model is not extensible. There is an infinite amount of things which could be included or excluded from any given assertion (i.e. are optional). For example, why is role type not mandatory for used links, or location or authorship not mandatory for of entities, etc. when making them so would also help the data structures be more uniform? You say "If you have relations without roles, you will have to define their meaning", but you could equally say "If you have entities without location, you will have to define their meaning" - it doesn't have to be that there is an "unspecifiedLocation", just that location is one of many things you have not asserted. Thanks, Simon > My view here is that we define a *conceptual* model. > Given serialization should make sure that shortcuts are provided. > The model itself provides one, so you don't need to write unspecified0, ... > > Data structure? PIDM is a data model. > > Surely, you know the implication of optional columns in > relational tables, and their implications on queries. > It's the same in the semantics. If you have relations wihtout > roles, you will have to define their meaning. > > Luc > > On 25/08/11 15:18, Simon Miles wrote: >> Hi Luc, >> >> It was not me that originally raised it, but I feel that the original >> issue (whether it will make sense to a reader why we require roles to >> be mandatory) is not fully resolved. >> >> I don't dispute that replay comes up as a use case occasionally, and >> maybe that's a reason to retain role names in the core model, but that >> does not help explain why roles should be mandatory in all provenance. >> Using "unspecified0, unspecified1, unspecified2, ..." seems ugly, >> unintuitive and restrictive, and so could dissuade people from using >> the standard. >> >> Moreover, I don't find the current model's rationale for this has >> enough context to make sense: >> "Roles are mandatory since they allow for uniform data structures." >> What data structures, who wants them to be uniform, and why? >> >> Should (can?) I re-open the issue? >> >> Thanks, >> Simon >> >> On 22 August 2011 22:12, Luc Moreau<L.Moreau@ecs.soton.ac.uk> wrote: >> >>> Hi Graham, >>> This issue was closed, pending review. >>> Are you satisfied with the changes? Can we >>> close it? Alternatively, you can reopen it, >>> or create a more specific issue. >>> Thanks, >>> Luc >>> >>> PS See note on this issue's page >>> >>> >>> >>> On 29/07/11 10:13, Provenance Working Group Issue Tracker wrote: >>> >>>> PROV-ISSUE-64 (definition-use): definition of use [Conceptual Model] >>>> >>>> http://www.w3.org/2011/prov/track/issues/64 >>>> >>>> Raised by: Graham Klyne >>>> On product: Conceptual Model >>>> >>>> 5.4 Use >>>> >>>> Same problem with 'role' as above. >>>> >>>> [[ >>>> A reference to a given BOB may appear in multiple use assertions that refer to a given process execution, but each of those use assertions must have a distinct role. >>>> ]] >>>> In light of the above, this seems nonsensical to me. >>>> >>>> [[ >>>> Given an assertion uses(pe,x,r) or uses(pe,x,r,t), at least one value of x's attributes is a pre-condition for the activity denoted by pe to terminate. >>>> ]] >>>> As written this doesn't make sense - a value of an attribute being a precondition seems like a type error to me. I think you mean something like availability of an attribute value. But even that is hard to follow. Suggest simplifying this to just: >>>> [[ >>>> Given an assertion uses(pe,x,r) or uses(pe,x,r,t), existence of x is a pre-condition for the activity denoted by pe to terminate. >>>> ]] >>>> >>>> >>>> >>>> >>>> >>>> >>> >>> ______________________________________________________________________ >>> This email has been scanned by the MessageLabs Email Security System. >>> For more information please visit http://www.messagelabs.com/email >>> ______________________________________________________________________ >>> >>> >> >> >> > -- Dr Simon Miles Lecturer, Department of Informatics Kings College London, WC2R 2LS, UK +44 (0)20 7848 1166
Received on Wednesday, 31 August 2011 14:05:32 UTC