RE: PROV-ISSUE-1 (define-resource): Definition for concept 'Resource' [Provenance Terminology]

I'd say that the concept of the ship as a 'legal' entity and as a
collection of physical parts are both equally valid abstractions that
could be defined as resources (given a URI and descriptive metadata). At
one point in time, those two resources coincide/are aspects of each
other/are aliases, but one is mutable with respect to 'part replacement'
events and one is not, so they are not aliases for all time. I'd like
the provenance model to allow both resources and to allow the 'aspect
of' link to be made so I can stick the provenance of the 'legal' ship
and the physical ship together (if the legal ship moved between ports
and there are no replacement events, I can conclude that the parts are
all at the new port as well...)




[] On Behalf Of Paolo Missier
Sent: Thursday, June 02, 2011 10:23 AM
To: James Cheney
Cc: Graham Klyne; Paolo Missier;
Subject: Re: PROV-ISSUE-1 (define-resource): Definition for concept
'Resource' [Provenance Terminology]


James, Graham (will address Luc's comments on the wiki again separately)

I would argue that the provenance of the car includes all the engine
replacements that took place, so if the engine is now B, I would like to
ask the question "why is B here?" and receive an answer like "B has
replaced A [at time t] [because A failed...]". I believe James hinted at
this. And if you are interested, you go back and unfold the history of
A. So yes, the provenance of A is still part of the car's provenance, in
the car's current state -- the logbook of car repairs that you get from
your garage is a simple example.
All I meant to say is that history is cumulative and immutable. That is
not to say it's linear. Someone else (sorry, mail chaos at this point)
commented that it is a DAG, and I would agree without having thought too
hard (which I never do :-)). 
  The issue of scoping / avoiding the big bang problem is addressed
separately: you may decide to prune the early episodes in history for
convenience, engineering issues, etc., and for most resources (whatever
your definition), there is some kind of origin. It's often relative to
the observer (as is all provenance): consumers generally don't need to
investigate where the engine's materials come from, whereas a forensic
epert investigating an engine failure may.

In my view, Theseus's ship is the result of all the actions that were
ever taken on it, including the destructive ones. Too radical?


On 6/2/11 12:41 PM, James Cheney wrote: 

Yes, these issues seem intuitive only as long as you don't stop to think
about them too hard :) 


I would say that the provenance has to be scoped by (say) a start and
end time, or some other criterion, to prevent the "big bang" problem
(see e.g. [Miles IPAW 2006]).  


If we want the provenance of the car from "now" until it was made, then
the provenance of A needs to be included (e.g., maybe A caused damage to
the car when it failed, so we need to know that to understand how the
car's current state was obtained from its initial state).


If we want the provenance of the car from "now" until I bought it, which
happened after the engine was replaced, then maybe I don't need to know
about A.  (If I want to buy the car, I'd probably value the knowledge of
the earlier history so that I can understand its current state, but the
seller isn't always obligated to provide this.)


This reminds me of another good story: 


The ship wherein Theseus <>  and the
youth of Athens <>  returned [from
Crete <> ] had thirty oars, and was
preserved by the Athenians down even to the time of Demetrius Phalereus
<> , for they took away
the old planks as they decayed, putting in new and stronger timber in
their place, insomuch that this ship became a standing example among the
philosophers <> , for the
logical question of things that grow; one side holding that the ship
remained the same, and the other contending that it was not the same.

-Plutarch, Theseus []


What is the provenance of the ship?  Was the ship really "preserved"?




On Jun 2, 2011, at 12:05 PM, Graham Klyne wrote:

I think Paolo has usefully threaded a path through our discussions.
Thanks!  At first reading, I would consent (in the sense of "consensus")
to definitions framed on the basis of what he has written here.


The issue of monotonicity (of provenance of a stateful resource) is
interesting. Intuitively, it seems appropriate, but I'd need to let it
stew awhile before accepting it unconditionally.  My immediate concern
is how do we account for correction of previous errors in provenance
claims?  But this question goes to the heart of what is, IMO, one of the
key purposes of provenance on the Web (i.e. to help deal with
conflicting information in the Web, and the Semantic Web in particular),
so maybe that point gets addressed separately in any case.

Aha!  I just thought of another example:  suppose we're talking about
provenance of a car (e.g. for QA purposes).  Initially, suppose it has
engine A, made by a particular factory.  The provenance of the car
include the provenance of engine A.  Sometime in its life, the engine
fails and is replaced by engine B, and provenance of engine C becomes
part of the car's provenance.  At this point, does it make sense to
claim that the provenance of A is still part of the car's provenance?  A
similar example could be constructed for, say, a photo album where
images are added and removed.



Received on Thursday, 2 June 2011 15:03:32 UTC