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Re: entity, creation and destruction

From: Paul Groth <p.t.groth@vu.nl>
Date: Fri, 16 Mar 2012 10:41:22 +0100
Message-ID: <4F630AC2.5070200@vu.nl>
To: Ted Thibodeau Jr <tthibodeau@openlinksw.com>
CC: Provenance Working Group WG <public-prov-wg@w3.org>
Hi Ted,

These are good examples and good motivation for having a construct that 
corresponds to generation in the model.

Paul

Ted Thibodeau Jr wrote:
> We were discussing "entity" again today...
>
> At least one person defined "entity" as "a description of a thing"
> based on the definition they read here --
>
>     http://www.w3.org/2011/prov/wiki/FormalSemanticsStrawman#Entities
>
>     An entity is a kind of object that describes a time-slice
>     of a thing, during which some of the thing's attributes
>     are fixed.
>
> I submit that an "entity" is a "thing" which is identified by
> some set of immutable characteristics (which set may or may not
> be fully defined -- much as philosophy continues to debate what
> set of immutable characteristics defines a particular person,
> the more so given such personality changes as may be observed
> following various injuries or pharmaceutical treatments).
>
> When an immutable characteristic changes, one entity becomes
> another.  When a mutable characteristic changes, the entity
> remains the same, but its description (and one might say, its
> provenance) changes.
>
>
> That discussion arose in context of the "Entity Invalidation"
> proposal found here --
>
>     <http://dvcs.w3.org/hg/prov/raw-file/default/model/working-copy/wd5-prov-dm-misc.html#Proposal%201:%20On%20Entity%20Invalidation>
>
> The examples seen there were confusing (conflating a web address
> with the entity/ies to which the address may be dereferenced) and
> not compelling to the audience at hand.
>
> I had some hopefully more compelling, and also hopefully less
> confusing, examples which I was asked to post to the list.
>
> Herewith...
>
>
> A "tree" comprises some amount of "wood".  When the "tree" is
> felled, one might say it is no longer a "tree" (it no longer
> stands; the stump which remains was once an integral part of
> the tree; it no longer sprouts leaves; etc.)...
>
> Let us say that the wood which comprised the bulk of that tree
> is transformed into a table.
>
> The table is a new entity -- immutable characteristics include
> the carpenter who constructed it, the "tabletop" surface on
> which things may be placed, and the legs which hold it off the
> floor.
>
> Mutable characteristics not relevant to its "table-ness" include
> its color, its exact shape, its height. I might cut a round table
> into a square, paint it, or shorten its legs, without it becoming
> a new entity.
>
> If any of the immutable characteristics are removed or destroyed
> -- for instance, if the whole is broken into pieces such that it
> cannot perform as a table -- the "table" entity is no more.
>
> However -- the wood remains.
>
> In the framework of the "entity" definition I quoted earlier, the
> "table" is a time-slice of the "wood".  The *tree* is a time-slice
> of the "wood".  Many characteristics of the wood change -- but it
> remains the wood of the original tree.
>
> At some point, the wood -- even the entire table -- may be thrown
> on a bonfire, and the entirety may be consumed.
>
> The table entity is no more -- the required characteristics are
> no longer present.
>
> The *wood* entity is no more -- it has been consumed by fire, and
> transformed into ash.
>
>
> During the call, I suggested another example which (I think) lends
> strong support to the need for a "destruction" or similar construct
> which corresponds to "generation" or "creation".
>
> A "Great Master" "creates" a "painting".  The "painting" "hangs"
> in a "museum".  The "museum" and all works therein are "consumed"
> by a "fire".  Witnesses see this particular "painting" so "consumed".
> Years later, a "painting" looking very much like the original comes
> up for auction...
>
> Real-world Provenance cries out for the ability to say that the
> museum piece *was* destroyed, so this work being auctioned
> *cannot* be (or at least, it is highly doubtful that it is) the
> same entity.  Real-world Provenance also allows for the possibility
> that the entity consumed in the fire was not the "original" which
> is now on auction -- that the burned painting was a forgery...
>
> But *something* was burned, was destroyed, can no longer be sold.
>
>
> Hopefully this exploration is helpful ...
>
> Regards,
>
> Ted
>
>
>
>
> --
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> | Q: Are you sure?
> | | A: Because it reverses the logical flow of conversation.
> | | | Q: Why is top posting frowned upon?
>
> Ted Thibodeau, Jr.           //               voice +1-781-273-0900 x32
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-- 
Dr. Paul Groth (p.t.groth@vu.nl)
http://www.few.vu.nl/~pgroth
Assistant Professor
Knowledge Representation & Reasoning Group
Artificial Intelligence Section
Department of Computer Science
VU University Amsterdam
Received on Friday, 16 March 2012 09:44:19 GMT

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