Re: [Spam:***** SpamScore] Re: formal semantics strawman

I think I missed the point at which IVPof went away in favor of
complementOf. I'm not sure what complementOf is attempting to do. I thought
I had a handle on IVPof, but complementOf seems a mystery. Where should I
look to find those semantics, and how they support the functionality of
IVPof?

Thanks,
Jim

On Sat, Aug 27, 2011 at 12:43 PM, Myers, Jim <MYERSJ4@rpi.edu> wrote:

> Trying to catch up after travel. I'm not sure I have the big picture but a
> few comments about statements in the thread:
>
> We need to avoid saying entities are fixed and ?things are not - entities
> are fixed in some ways - defined by attributes with values, but they are
> mutable in other ways. ?things can be this way as well and we may assert
> entities that have the same ID as an existing ?thing - because that thing is
> already defined as fixed in the ways we need it to be for provenance, or we
> may assert entities that are 'complements' of ?things when we need to fix
> more attributes or different attributes than for the ?thing itself.
>
>  The interval over which an entity exists may be different than the one for
> which a complementof relationship is true. If we want an asserted entity
> that is is the fixed content at a live URL, it should have its own ID and a
> complementof relationship with the site URL(a ?thing and potentially another
> entity if we wish to discuss the provenance of the live site itself). The
> complementOf relationship is true until the site content updates, but the
> fixed page entity could still exist. I think this is consistent with the
> discussion but am not sure.
>
> The interpretation of an entity should be time invariant - one can choose
> to assert an entity that is a fixed web page or one for a a live website,
> but one should not have an entity asserted with a content property as part
> of its definition and then have that property change. For the example.comexample, one can define an entity that is 'the content available from the
> example2.com site no matter what URL you get it from'' (retrieval URL
> can't be an attribute here) or one that is 'the content retrievable from
> example2.com' that is generated by the site starting operations and ceases
> to exist when the site URL is blocked from the world/retired (retrieval URL
> can be an attribute here). Either is valid - the point with an entity is
> that you are picking one definition and sticking with it, using complementof
> when you need to switch definitions.
>
> Hope those are helpful  in the larger discussion (and consistent with
> others interpretation!)...
>
> Jim
> ________________________________________
> From: public-prov-wg-request@w3.org [public-prov-wg-request@w3.org] on
> behalf of James Cheney [jcheney@inf.ed.ac.uk]
> Sent: Friday, August 26, 2011 7:17 AM
> To: Graham Klyne
> Cc: W3C provenance WG
> Subject: [Spam:***** SpamScore] Re: formal semantics strawman
>
> On Aug 25, 2011, at 6:59 PM, Graham Klyne wrote:
>
> > James,
> >
> > Thanks.  This help to clarify for me some things that weren't clear to me
> in the model document.
> >
>
> Note that the strawman is not necessarily capturing the intent of the model
> document (it just represents my initial effort to interpret it formally) so
> might be misleading about what it was trying to say.  For example, Luc asked
> me offline to change what I was calling "entity" to something else because
> it doesn't match the model.
>
> I've now updated the document to avoid this potential confusion between the
> PIDM assertion "entity" and the semantic "?things".  (The question mark is
> there to flag it as a term with special meaning; we should probably find a
> less generic term)
>
> > You say at
> http://www.w3.org/2011/prov/wiki/FormalSemanticsStrawman#Interpreting_an_entity_assertion
> :
> > [[
> > Note that there is a design choice here: do we require that the entity
> associated with id be the same throughout the interval or not? I have chosen
> to require this, since otherwise the entity assertion doesn't seem to be
> about a "single entity across a time interval". Of course, if we require
> that the mapping from URIs to entities be time-invariant then this problem
> goes away.
> > ]]
> >
> > As far as I can tell from a quick skim, everything else works as intended
> (at least in sections 1.3, 1.4) if the URI->Entity mapping is invariant.
>  Which I think leads to a model in which the distinction between resource
> and entity (which I find to be unhelpful) becomes less significant.
> >
>
> I was thinking of a situation where a URI is "retired" and redirected to a
> different target, e.g. example.com merges with example2.com, and
> http://www.example2.com is redirected to example.com's website from then
> on.  Perhaps in this example http://www.example2.com is by definition not
> a URI.
>
> I think assuming that lookup is time-insensitive would be reasonable (and
> would definitely simplify some of the definitions), but wanted to highlight
> the design choice since it seems related to things that have been debated on
> the list.  I'd rather keep things more general now until it's clear that
> there's consensus about a consistent picture with the other related
> components.  If it is then obvious that time-variance in the interpretation
> of URIs is superfluous then it'll be easy to eliminate it.
>
> --James
>
>
> > #g
> > --
> >
> > On 25/08/2011 18:13, James Cheney wrote:
> >> Hi,
> >>
> >> I've been promising for a while now to write down a short formal
> semantics strawman to illustrate what I have in mind.  I've put something
> onto the wiki here:
> >>
> >> http://www.w3.org/2011/prov/wiki/FormalSemanticsStrawman
> >>
> >> It's definitely not a finished product but I've made an effort to cover
> entity assertions, ivp/complement, process execution, and events (but NOT
> derivation :)
> >>
> >> One thing that's become apparent already is that there is a large
> potential for confusion since we are talking about assertions about things
> that may change over time.  The assertions may explicitly mention time
> points/intervals and they may also implicitly have "assertion time" or "time
> intended to be valid"  associated with them. Some of the assertions in the
> Conceptual Model document also have explicit times associated with them
> (e.g. use, generation and process execution assertions.)  Others such as
> entity assertions do not have explicit time arguments, but the discussion
> surrounding them refers to time points or intervals during which the entity
> being described exists.
> >>
> >> So for each kind of assertion p(x,y,z,...), it would be helpful to
> clarify whether:
> >> 1.  p(x,y,z,...) is something that either always holds or never holds;
> or
> >> 2.  p(x,y,z,...) can hold or not at a specific point in time t (there
> may be a convention that we can make this explicit by adding an argument,
> e.g. p(x,y,z,...,t)); or
> >> 3.  p(x,y,z,...) can hold or not during an interval [t1,t2] (again there
> may be a convention where we add 2 arguments).
> >>
> >> Currently, there seem to be a mix of conventions.
> >>
> >> Comments are welcome.  I'm not pretending to have read all the relevant
> background / mailing list discussion carefully and so I may be using
> terminology incorrectly.  As the name suggests, I expect this to be easy to
> knock down, but hope that we'll learn something in doing so anyway.
> >>
> >> --James
> >
> >
>
>
> --
> The University of Edinburgh is a charitable body, registered in
> Scotland, with registration number SC005336.
>
>
>
>
>


-- 
Jim
--
Jim McCusker
Programmer Analyst
Krauthammer Lab, Pathology Informatics
Yale School of Medicine
james.mccusker@yale.edu | (203) 785-6330
http://krauthammerlab.med.yale.edu

PhD Student
Tetherless World Constellation
Rensselaer Polytechnic Institute
mccusj@cs.rpi.edu
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