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Re: Different senses of specialization

From: Tom De Nies <tom.denies@ugent.be>
Date: Thu, 12 Apr 2012 15:14:13 +0200
Message-ID: <CA+=hbbexc0+O-hZS_-34JSjmERVXgki0aPFFqsNGW=TJatDkHg@mail.gmail.com>
To: James Cheney <jcheney@inf.ed.ac.uk>
Cc: Graham Klyne <graham.klyne@zoo.ox.ac.uk>, Luc Moreau <L.Moreau@ecs.soton.ac.uk>, ProvenanceWorking Group WG <public-prov-wg@w3.org>
I think a lot of this would make more sense, and significantly simplify the
definitions in PROV-DM, if the attribute-value pairs that are mentioned in
the PROV-CONSTRAINTS entity definition are included in PROV-DM from the
very start.

The fact that we are questioning our definition of the most basic component
of the data model at this stage, near completion, is a clear indication
that we are over-engineering this somewhat. Upon reading the constraints, I
also found it to be strange that suddenly a new definition of entity is
given.

I thought the DM WD4 definition was quite clear:

> *Entities are things in the world one wants to provide provenance for.
> For the purpose of this specification, things can be physical, digital,
> conceptual, or otherwise; the world may be real or imaginary.*

 Add to this the further refinement of the constraints:

> *An entity is a thing one wants to provide provenance for and whose
> situation in the world is described by some attribute-value pairs. An
> entity's attribute-value pairs are specified when the entity description is
> created and remain unchanged.*

And you get this:

> *An entity is a thing one wants to provide provenance for and whose
> situation in the world is described by some attribute-value pairs. **For
> the purpose of this specification, things can be physical, digital,
> conceptual, or otherwise. **An entity's attribute-value pairs are
> specified when the entity description is created and remain unchanged.*


This further simplifies the definition of alternateOf and specializationOf.
Then I would propose something like this:

alternateOf: *Two entities are alternates if they are the same thing, but
their situation in the world is described by different attribute-value
pairs. *

specializationOf: *An entity is a specialization of another entity if they
are the same thing, and the description of the situation in the world of
the former includes all of the attribute-value pairs of the latter, and at
least one more.*

That also eliminates some discussion about transitivity/reflexivity, since
we would then have a concrete, measurable definition.

Of course this is only a suggestion, and I could be missing something here.

Best regards,
Tom
---
Tom De Nies
Ghent University - IBBT
Faculty of Engineering and Architecture
Department of Electronics and Information Systems - Multimedia Lab
Gaston Crommenlaan 8 bus 201, B-9050 Ledeberg-Ghent, Belgium

e: tom.denies@ugent.be

URL:  http://multimedialab.elis.ugent.be



2012/4/12 James Cheney <jcheney@inf.ed.ac.uk>

>
> On Apr 12, 2012, at 8:35 AM, Graham Klyne wrote:
>
> > On 12/04/2012 00:01, Luc Moreau wrote:
> >> Hi Graham
> >> Can you do without 'version', which carries its own meaning in the
> context of provenance?
> >
> > Yes... I wanted to avoid that, but couldn't think of another word that
> didn't beg even more questions.
> >
> >> Are you saying a description *is* a thing? Or denotes a thing.
> >
> > Neither.  A description *describes* something; provides information
> about that something.
> > In the general context here, a provenance expression describes an entity,
> > hence also describes some aspect of a thing.
> >
> >> Also, what is the meaning for 'more specific thing'.?
> >
> > Ultimately, the formalization says it precisely.
> > My main concern is trying to avoid use/mention confusion in the informal
> text.
> >
>
> Actually, the formal semantics tries had *not* to try to answer too many
> questions like this!
>
> I'm realizing that by doing so, I've been hopscotching the central issue
> about the entity/thing description: I think the consensus is emerging that
> (cf Tim's comments also) entities are a
>
> *special things (or parts of things) that are well-behaved enough that we
> can describe*
>
> The semantics doesn't commit to this reading because I wasn't sure in
> working on it whether entities were *separate information about things*
> (informational reading), or whether the entity records are records that
> describe entities that are *particular aspects of things* (whole/part
> reading).
>
> The fact that (for a while) we were talking about specialization partly in
> terms of the attributes declared in the entity records made me think we
> were talking about information, but now it seems that the latter
> (whole/part) reading  is closer to the consensus, and we need to explain
> this very carefully.
>
> Graham and others, are you happy with the following refinement:
>
> "alternateOf: To express when one Entity is an aspect of the same Thing as
> another Entity. "
>
> "specializationOf: To express when one of two alternate Entities
> encompasses more specific aspect(s) of the Thing they are both based on"
>
>
> > #g
> > --
> >
> >>
> >> Professor Luc Moreau
> >> Electronics and Computer Science
> >> University of Southampton
> >> Southampton SO17 1BJ
> >> United Kingdom
> >>
> >> On 11 Apr 2012, at 15:14, "Graham Klyne"<graham.klyne@zoo.ox.ac.uk>
>  wrote:
> >>
> >>> James,
> >>>
> >>> I think what you write here in response to Luc is just right.
> >>>
> >>> I also think that the point of Luc's previous question may be a
> reaction to some unfortunate phrasing, where you (were quoted to) say:
> >>>
> >>> "specializationOf_1: To express when one entity provides a more
> specific description of the same thing as another entity."
> >>>
> >>> I think this might be more precisely phrased as something like:
> >>> "specializationOf_1: To express when the description of one entity is
> a more specific version of the same thing as the description of another
> entity."
> >>>
> >>> I.e. to make it clear that is is not the entity itself that provides a
> description, but is described.
> >>>
> >>> (I also considered:  "specializationOf_1: To express when the
> expression for one entity is a more specific description of the same thing
> as the expression for another entity." - but this introduces the notion of
> an expression for an entity, which I'm not sure is helpful.)
> >>>
> >>> #g
> >>> --
> >>>
> >>> On 11/04/2012 12:04, James Cheney wrote:
> >>>> Hi,
> >>>>
> >>>> Specialization and alternate are relations between entities in the
> semantics.
> >>>>
> >>>> Saying that "entities are things" is vague: does it mean "all
> entities are things", or does it also mean "entities and things are the
> same concept"?  Can you please refer me to the resolution text on this
> point?
> >>>>
> >>>> Does this mean that "all entities are things"? This is sensible, and
> is allowed but not required by the semantics.
> >>>>
> >>>> Conversely, does it mean "all things are entities"?  We've been using
> "Thing" to talk about things that can change over time, whereas entities
> are fixed aspects of such things - which we need in order to provide
> provenance records that are stable over time.  So if we say "all entities
> are things, AND all things are entities" then this distinction disappears
> and becomes purposeless.
> >>>>
> >>>> An Entity could be a Thing in the semantics.  The semantics doesn't
> say whether entities are things or not.  All it prescribes are
> >>>>
> >>>> - each Thing has a lifetime and some attributes that can vary
> >>>> - each Entity has a lifetime and some attributes which don't vary
> >>>> - each Entity is formally linked to a Thing with a larger lifetime,
> by a function thingOf.
> >>>>
> >>>> : the sets of entities and things could be any sets and could
> overlap.  However, any Thing in an instance of the semantics that chances
> over time cannot be an Entity.
> >>>>
> >>>> One can think of the thingOf function in different ways.  I tend to
> think of the entities as "information about things", with the thingOf
> function linking the entity to the thing that it is about, but I understand
> that this perspective isn't widely shared.  I'm happy to rephrase it if we
> can find a more agreeable term.
> >>>>
> >>>> Would these rephrasings be OK with you (and others, especially Tim):
> >>>>
> >>>> "alternateOf: To express when one Entity is an aspect of the same
> Thing as another Entity."
> >>>>
> >>>> "specializationOf: To express when one of two alternate Entities is
> more a specific aspect of the Thing they are both based on"
> >>>>
> >>>> --James
> >>>>
> >>>> On Apr 11, 2012, at 6:14 AM, Luc Moreau wrote:
> >>>>
> >>>>> Hi James,
> >>>>>
> >>>>> I have some difficulty with your descriptions of specialization.
> >>>>>
> >>>>> "specializationOf_1: To express when one entity provides a more
> specific description of the same thing as another entity."
> >>>>>
> >>>>> This seems to indicate that an entity is a description of a thing.
> >>>>>
> >>>>> It thought that an entity *IS* a thing, and we provide descriptions
> for entities. So, I don't think that an entity
> >>>>> describes something.
> >>>>>
> >>>>> A long time ago, I asked if specialization/alternate were relations
> between descriptions or between entities. The
> >>>>> group responded these relations were between entities!
> >>>>>
> >>>>> Given this, does your classification still hold? Can it be phrased
> differently?
> >>>>>
> >>>>> Luc
> >>>>>
> >>>>> On 11/04/2012 05:43, Luc Moreau wrote:
> >>>>>> Tracker, this is ISSUE-29.
> >>>>>>
> >>>>>> Professor Luc Moreau
> >>>>>> Electronics and Computer Science
> >>>>>> University of Southampton
> >>>>>> Southampton SO17 1BJ
> >>>>>> United Kingdom
> >>>>>>
> >>>>>> On 9 Apr 2012, at 15:58, "James Cheney"<jcheney@inf.ed.ac.uk>
>  wrote:
> >>>>>>
> >>>>>>
> >>>>>>> Hi,
> >>>>>>>
> >>>>>>> In reading the discussion over the last week and while reviewing
> the various documents, I've noticed that "specialization" seems to be being
> used in (at least) three different ways.  I think this is a contributor to
> the confusion concerning specialization and alternate.
> >>>>>>>
> >>>>>>>
> >>>>>>> specializationOf_1: To express when one entity provides a more
> specific description of the same thing as another entity.
> >>>>>>>
> >>>>>>> Example: The entity ex:article in the primer, with its versions
> ex:articleV1 and ex:articleV2, both of which are specializations of
> ex:article.
> >>>>>>>
> >>>>>>> This is the sense that I have been assuming and it is what is
> reflected in the semantics.
> >>>>>>>
> >>>>>>>
> >>>>>>> specializationOf_2: To express when one entity provides more
> specific information than another (which need not be about the same thing!)
> >>>>>>>
> >>>>>>> Example: In PROV-DM-CONSTRAINTS:
> >>>>>>>
> >>>>>>> specializationOf(customerInChairAt6pm, customerInChair)
> >>>>>>> specializationOf(customerInChairAt7pm, customerInChair)
> >>>>>>>
> >>>>>>> To me this does not make sense because the entities
> customerInChairAt6pm and customerInChairAt7pm are about different "Things"
> (the different customers Alice and Bob).  So there is no single Thing to
> which customerInChair describes, contradicting (what I thought was) the
> consensus that an entity describes an aspect of exactly one thing.
> >>>>>>>
> >>>>>>> In my view, this sense of specialization is specious, since one
> entity may provide "more specific" information than another entity but the
> two entities need not be about the same thing, as the relationship may be
> purely coincidental.  To carry this to an extreme, any entity is a
> "specializationOf(2)
> >>>>>>>
> >>>>>>>
> >>>>>>> specializationOf_3: (work / item) To express when one entity
> describes a more concrete thing that is an instance of a more abstract
> thing described by another entity.  This is like the work/item distinction
> in FRBR.
> >>>>>>>
> >>>>>>> Example: The primer refers to a file (which can have multiple
> versions), and a specific copy of a file on  a hard disk, as another
> example of specialization.
> >>>>>>>
> >>>>>>> To me this does not make sense because a file, in the abstract, is
> just a sequence of bits, which could be physically realized anywhere or
> could be realized in multiple places at once.  A file-on-disk might carry
> the same information as an abstract-file, but can only exist in one place.
>  We do not talk about locations explicitly in PROV, but even so, I think
> this is confusing: again, to carry the argument to an extreme, the number
> 2, in the abstract, is not the same kind of thing as a piece of paper with
> "two" written on it.
> >>>>>>>
> >>>>>>> I think specializationOf_3 ("instance/realization of") is a
> sensible notion, but it should not be conflated with specializationOf_1.
>  There are already vocabularies that deal with this type of relationship,
> such as FRBR itself.  If we believe that PROV should attempt to solve this
> in a new way, I think we should avoid overloading the notion of
> specialization as "different, more specific information about the same
> thing" with this notion, which is really about "more concrete instance of
> an abstract thing"
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>> To summarize:
> >>>>>>> - I think we should be careful about these different senses of
> "specializationOf".
> >>>>>>> - Only the first sense is supported by the current version of the
> semantics.
> >>>>>>> - If we can agree on one of these definitions for
> specializationOf, but believe other senses need to be modeled, we should
> introduce additional relations to name them, and ensure that the meanings
> are clear and they are used consistently in examples.
> >>>>>>>
> >>>>>>>
> >>>>>>> --James
> >>>>>>> --
> >>>>>>> The University of Edinburgh is a charitable body, registered in
> >>>>>>> Scotland, with registration number SC005336.
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>
> >>>>>
> >>>>
> >>>>
> >>
> >>
> >
> >
>
>
> --
> The University of Edinburgh is a charitable body, registered in
> Scotland, with registration number SC005336.
>
>
>
Received on Thursday, 12 April 2012 13:14:49 GMT

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