RE: smaller example

 

 

From: Satya Sahoo [mailto:satya.sahoo@case.edu] 
Sent: Wednesday, June 15, 2011 9:56 PM
To: Myers, Jim
Cc: Provenance Working Group WG
Subject: Re: smaller example

 

Hi Jim,

I wanted to clarify the following point:

> * there is/are mutable property(ies) of A that is/are correspond to
immutable property(ies) of B (i.e. ones that are integral to B's
identity)

 

If a set of property(s) are integral to B's identity (and immutable),
while they are mutable for A - are these property(s) integral to A's
identity also? 

 

No. An example is the discussion of file container A (has a name/path on
disk and mutable content) versus a file-as-fixed-set-of-bytes B (has
name/path and a fixed content).

 

Case I: If they are integral to A's identity I am not sure how can they
be mutable, else 

 

Case II: If they are not integral then how can A and B represent the
same entity/part of the world (at any specific point in time) since the
set of identifying property(s) of two identical entities will also be
identical? 

I view this as A and B representing the same 'stuff' through the lens of
two different theories/object models of the world. I can see files as
mutable containers or as fixed things. At a given point in time, the
theories/object models should allow agreement on what 'stuff' is being
discussed/modeled by specific things (identified instances in those
theories/models) - I can agree that my named file A actually has the
content that means it the thing you think of as immutable file B.

> * If B is an IVP of A, they must have the same values for all
immutable

properties they have in common (for their entire existences...).

Agree (identifying property(s) of an entity cannot change without
changing the identity of the entity)


>* The distinction between A and B becomes relevant when one is
discussing processes that affect the aspects of entity state represented
by the subset of properties that represent the shift of some aspect of
state from mutable in A to immutable in B. 

This point does not follow from the previous point. Can we say that A
and B share mutable property(s) that have different values hence
accounting for the different perspectives/views?

 

At the time at which A and B are in an IVP relationship, all of their
properties must be consistent. If they have the same properties, they
must have the same values. The odd language was meant to take into
account cases where, for example, an egg might have a %cracked property
(mutable) and the immutable views might just be crackedEgg and wholeEgg,
or a mutable file may have only a logical content bytestream whereas the
immutable version has a fixed format (e.g. zipped) and actual
bytestream. Basically accepting that when one considers something part
of state to be immutable, the set of properties that make sense to
describe it might change (or simply the group of people who described
the immutable thing and those who looked at the mutable one picked
slightly different property-level descriptions).

 

This is a general point: I have tried to follow the discussion threads,
both the original thread on IVPT and the subsequent thread on Luc's
smaller example, but unfortunately I am still not sure how the IVPT
concept is applicable to the current data journalism example.

 

I think the exact mapping is still tbd, but I think both the idea of
sources (mutable things that publish documents) fits and we have some
idea of publishable document that 'sort of' overlaps with the idea of
physical files (perhaps clearest if we wanted to talk about a file being
moved into the place where it will be served as being separate from the
event that marks the content of that file as being 'published'). I think
we'll need IVP to deal with this and other aspects of that scenario -
but still an action for someone to actually do it so we can assess the
fit.

 

Cheers,

Jim

 

Thanks.

 

Best,

Satya

 

 

On Mon, Jun 13, 2011 at 2:30 PM, Myers, Jim <MYERSJ4@rpi.edu> wrote:

FYI - Luc and I had a Skype call this morning to discuss a path forward
on how to address invariance and we have tried to combine aspects of
both alternatives from the working group discussion in a way that
hopefully works and can gain consensus. A few more details below, but
the general path is to model with one type of thing (ala IVP of T) but
to push the definition of that type of thing to be independent of
processes (ala IVPT). The question for the group is then whether this
makes sense/looks like it helps/is consistent with other views/should be
elucidated further, etc.

Cheers,
  Jim


The following is my embellishment of what Luc and I discussed -
hopefully still consistent with our discussion :-) I expect some further
refinement will be needed to nail everything down.

Definition of 'thing': In PIL, entities in the real world (described in
terms of physical, digital, logical, conceptual, other vocabularies) are
modeled as "things" that:
* have an identity
* model aspects of the entity's state as a set of properties of the
"thing" that are invariant and considered integral to identity
* model other aspects of the entity's state as a second set of
properties that are mutable and able to change during the "thing"'s
lifecycle, and therefore not integral to identity

There are no assumptions that the sets of properties are complete as
documented, or that the properties are independent/orthogonal of each
other.

Definition of "invariant view/perspective" (IVP):

For A and B, both of which are "things", B is an  IVP of A iff
* A and B represent the same entity/part of the real world at some
instant in time (the set of properties they share must have identical
values at that instant), and
* there is/are mutable property(ies) of A that is/are correspond to
immutable property(ies) of B (i.e. ones that are integral to B's
identity)

These definitions then have a number of implications:
* If B is an IVP of A, they must have the same values for all immutable
properties they have in common (for their entire existences...).
* The distinction between A and B becomes relevant when one is
discussing processes that affect the aspects of entity state represented
by the subset of properties that represent the shift of some aspect of
state from mutable in A to immutable in B. If B is an IVP of A at time
t, B is an IVP of A is true for the whole interval between processes of
this type.

Etc.



> -----Original Message-----
> From: public-prov-wg-request@w3.org [mailto:public-prov-wg-

> request@w3.org] On Behalf Of Luc Moreau
> Sent: Monday, June 13, 2011 5:35 AM

> To: Provenance Working Group WG

> Subject: smaller example

>
> Dear all,
>
> PROV-ISSUE-1
> PROV-ISSUE-8
> PROV-ISSUE-19
>
> On June 7th [1], we agreed on "In a first instance, to define the
necessary
> concepts that allow us  to express the provenance of an invariant view
or
> perspective on a thing".
> Putting this in practice turns out to be difficult.
>
> While the egg example is interesting, the scenario seems to evolve all
the
> time. Also, I thought that, in a first instance, we may want to look
at things
> that are digital, before seeing how our ideas extend to the
non-digital world.
>
> Obviously, we have our data journalism example, but we seem to ignore.
I
> think that we ignore it because:
> - it does not focus on changing things
> - it is not precise about how information is published/access,
> - it is quite long
> (I liked what Simon proposed for this example [2] and this inspired me
here)
>
>
> To unblock the situation, I have:
> - drafted a smaller example [3], focusing on a file being updated
> - tried to illustrate examples of IVPTs in this example
> - highlighted an example of IVPT that I don't know how to handle.
>
> In this example, it would be good to see
> - where we have consensus
> - where we have disagreement
> - how we handle the outstanding example (i0) of IVPT
>
> Feedback by email or on wiki welcome!
>
> Cheers,
> Luc
>
>
> [1]
http://lists.w3.org/Archives/Public/public-prov-wg/2011Jun/0096.html
> [2]
http://lists.w3.org/Archives/Public/public-prov-wg/2011Jun/0069.html
> [3] http://www.w3.org/2011/prov/wiki/FileExample
>
> --
> Professor Luc Moreau
> Electronics and Computer Science   tel:   +44 23 8059 4487
<tel:%2B44%2023%208059%204487> 
> University of Southampton          fax:   +44 23 8059 2865
<tel:%2B44%2023%208059%202865> 
> Southampton SO17 1BJ               email: l.moreau@ecs.soton.ac.uk
> United Kingdom                     http://www.ecs.soton.ac.uk/~lavm
>