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RE: Minutes / IRC log. SIMILE Telecon 30 May 2003

From: Seaborne, Andy <Andy_Seaborne@hplb.hpl.hp.com>
Date: Mon, 2 Jun 2003 10:05:09 +0100
Message-ID: <5E13A1874524D411A876006008CD059F06C23B96@0-mail-1.hpl.hp.com>
To: "'bass@mit.edu'" <bass@mit.edu>, "'www-rdf-dspace@w3.org'" <www-rdf-dspace@w3.org>

On item 2, specifically about finding the most recent version of the object,
there was also an observation by Kevin Smathers, that there could be an
explicit statement in the model to indicate that fact.  Then, a query can
find "latest" as  it is noted.  (This could also be done in OWL, with a
complement of a class expression that defines having a "follows" property.)


-----Original Message-----
From: bass@mit.edu [mailto:bass@mit.edu] 
Sent: 30 May 2003 18:59
To: www-rdf-dspace@w3.org
Subject: Minutes / IRC log. SIMILE Telecon 30 May 2003

We discussed three topics on the call, all in review of Jason's current 
history system design document:

1. How to extend data model (best practice):
     By Subclass?
     By Subproperty?

   Outcome: Need further discussion and clarification on list.

2. Capability/Utility of queries incorporating negative assertions

	JK: Useful/Required for certain history system query use cases.
	AS: There are alternative ways of modelling that don't require it.
	JK: Still unclear how to implement?

3. Producing Metadata Disseminations from Metadata in the History System

	JK: History System gathers metadata about state in past situations,
	    that can be queried.  Makes no assumption about what subgraphs
	    could/should be disseminated for particular URIs in the data
	AS: Should be able to http:get a name and receive metadata about it
	MB: What's missing is the mapping: what's the implied query that
	    determines the subgraph to return for the name.  Also (future)
	    could return disseminations that are not metadata, but content.

	JK to schedule additional telecon.  Timing logistics TBD on list.
	Bass to supply phone bridge.


[12:01] <mickBass> Attending:
[12:01] <mickBass> Kevin Smathers
[12:01] <mickBass> Mark Butler
[12:01] <mickBass> Jason Kinner
[12:02] <mickBass> Andy Seaborne
[12:03] <mickBass> Scribe: Kevin Smathers
[12:03] <mickBass> Backup Scribe: Mick Bass
[12:06] <kevins2> jk: design doc feedback request.  new update available, 
includes marks comments and new diagrams
[12:06] <kevins2> jk, dated may 28
[12:06] <kevins2> jk, will accept comments via email.
[12:07] <mickBass> http://web.mit.edu/simile/www/resources/history-
[12:08] * marbut has joined #simile

On extension of Data Model using Subclass and/or Subproperty
a.k.a. "Do/Should Subproperties vary meaning based on context?"

[12:09] <kevins2> jk, clarify date and event
[12:09] <kevins2> jk, defined explicitly in schema
[12:10] <kevins2> jk, i like subEventOf, but there is no use case for that
current simile
[12:11] <kevins2> mb, need refinements of date to refine example, or use 
subproperties from Harmony as an example
[12:12] <kevins2> mb, might be subclassed from dc:date, but dc:date is too 
general to use directly.
[12:13] <kevins2> jk, i have seen date used as property directly.  no idea 
what they were talking about in that case, has to be inferred.
[12:13] <kevins2> mb, semantic meaning of date changes according to context;

ie where it is referenced.
[12:14] <kevins2> jk, classes and properties with the same name?
[12:14] <kevins2> jk, created event, and created property.
[12:15] <kevins2> jk, need to be equated.
[12:15] <kevins2> jk, meaning is the same.
[12:17] <kevins2> jk, creates is subproperty of hasResult, destroys is 
subProperty of hasPatient, subproperty of involves
[12:17] <kevins2> range is an actuality
[12:18] <kevins2> discuss figure 5.
[12:18] <kevins2> jk, will it be clear how to extend schema 
[12:19] <kevins2> jk, event and property are defined by Harmony -- given
how to extend schema to other possible actions and events?
[12:19] <kevins2> jk, event and action are themselves too generic.
[12:19] <kevins2> jk, need new classes that are subclasses of event and
[12:20] <kevins2> jk, but these aren't acceptable to community.  need to
in the direction of specific classes with specific properties.
[12:20] <kevins2> jk, eg.: event modify should have subproperties that 
identify the record modified.
[12:21] <kevins2> jk, currently only using basic Harmony/ABC in the diagrams

(eg: Fig 6)
[12:22] <kevins2> jk, two issues -- can't use generic property that changes 
its semantics in the context of different classes.
[12:24] <kevins2> jk, secondly -- extending the schema by creating new 
subproperties for their implementation e.g transforms class representing 
action and event, + subproperties of hasresult that 
represent 'yieldsTransformation'.  Can't cleanly extend via classes, nor
properties.  Easier to use type of class as part of the query.
[12:24] <kevins2> jk, subproperty is harder to understand 
[12:25] <kevins2> jk, subclasses of actions and events are needed, but need 
subproperties as well to really help.
[12:28] <kevins2> bass, suppose i create a subclass of modified that is 
[12:28] <kevins2> range is ...?
bass: what's wrong with using hasResult with *domain* = transforms, without 
defining a subproperty?  (yes, I did say range on the call...)
[12:29] <kevins2> jk, does hasResult sufficiently model the semantics of 
modified in the sense of transform?
[12:30] <kevins2> bass, is it broken, or is it a user concern that the users

won't model it correctly?
[12:33] <kevins2> mb, users need guidance.
[12:34] <kevins2> mb, key problem is modelling, and there is no set of known

good practices.
[12:34] <kevins2> mb, digraphs are an unknown.
[12:34] <kevins2> jk, this model has some responsibility in detemining best 

On RDF/RDQL Query Capabilities wrt negative assertions?

[12:36] <kevins2> jk, andy -- about rdql -- is there a way to make a
assertion in the graph pattern?
[12:36] <kevins2> as, no closed world assumptions.
[12:37] <kevins2> jk, most recent version of the object; can't ask what is
object that doesn't have a successor.
[12:37] <kevins2> as, other ways to accomplish that -- a closed list that 
lists objects in creation order for example.
[12:39] <kevins2> jk, subqueries for example.
[12:40] <kevins2> as, does a subgraph pattern not exist is really what you
looking for
[12:43] <kevins2> jk, bass: discuss query results as linked list.
[12:43] <kevins2> as, there are more ways to examine a graph than by query.
[12:44] <kevins2> as, fine grained tests include exact tests for a 
[12:44] <kevins2> jk, for remote clients that won't work.
[12:44] <kevins2> jk, need to pose useful queries for haystack.

On producing Disseminations from Metadata in History System Store

[12:46] <kevins2> as, abstraction -- url per resource
[12:46] <kevins2> jk, unclear what URL producing metadata dissemination
be linked to.  history system can't predict 
[12:47] <kevins2> as, community, collection, ...
[12:47] <kevins2> jk, can't guarantee that handle resolves, or resolves to 
[12:51] <kevins2> discussion re handles
[12:52] <kevins2> as, history store can't be asked what it knows about
[12:53] <kevins2> bass, could be an implied query that returns data from the

[12:55] <kevins2> as, need to be able to ask history system what it knows 
about a particular object -- full data of the historical object.
[12:56] <kevins2> bass, issue is what data would be needed from an HTTP get.

One case is what metadata we want, the other is that the history system may 
need to roll back.
[12:56] <kevins2> jk, right now history system has no access to that 
[12:57] <kevins2> jk, can't produce disseminations based on these handles.
Received on Monday, 2 June 2003 05:06:29 UTC

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