F2F1 Minutes Session 1

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This is part of F2F1 Minutes

OWL Working Group Meeting Minutes, 06 December 2007

DRAFT. Currently Under Review

See also: IRC log



Welcome, Logistics, Introductions

Peter Haase

Boris Motik

Boris Motik: I'm boris motik, University of Oxford

Bernardo Cuenca Grau

Steve Battle

Jeremy Carroll

Peter Patel-Schneider

Uli Sattler

Carsten Lutz, Dresden (guest, joining)

Thomas Schneider (guest)

Michael Smith

Bijan Parsia

Sebastian Brandt (guest)

Matthew Horridge (guest)

Giorgos Stoilos

Pascal Hitzler

Markus Krötzsch

Vit Novacek

Ivan Herman

Sandro Hawke

Deborah McGuinness

Evan Wallace

Rinke Hoekstra

Sean Bechhofer (guest from Manchester)

Robert Stevens (guest from Manchester)

Ian Horrocks (University of Manchester [sic])

OWL 1.0 Implementation Experience

Speaker - Matthew Horridge - slides

Matthew Horridge: implementing OWL DL experience

Matthew Horridge: problems - RDF and imports

Matthew Horridge: internal API is known as the OWL API - based on OWL abstract syntax

Matthew Horridge: use of OWL API means that different concrete syntaxes can be used

Matthew Horridge: problems with abstract syntax - distinguishing between, e.g., data and object properties

RDF

Matthew Horridge: effort required - RDF parser is vast majority of effort, everything else is much easier

Matthew Horridge: similar situation for OWL 1.1 API

Ivan Herman: what is the "RDF parser"

Matthew Horridge: RDF parser is just triples to internal API, not dealing with RDF/XML

Matthew Horridge: RDF mapping - want to be fast, small, and streaming

Matthew Horridge: streaming was too hard, so the parser was not streaming

Matthew Horridge: in new parser - parser is streaming, but still takes resources

Matthew Horridge: OWL XML is very verbose - causes problems

Jeremy Carroll: what is the size increase

Matthew Horridge: not sure - 3 to 5 times

Matthew Horridge: triples to OWL API was problematic - inversing a non-deterministic mapping

Matthew Horridge: OWL 1.1 thus has two mappings

Matthew Horridge: e.g., subclass (see slides)

Matthew Horridge: other problem - n-ary constructs go to n or n*n triples

Matthew Horridge: failures of round tripping cause problems

Matthew Horridge: missing type triples make ontologies officially non-parsable

Matthew Horridge: in many cases there is a fix, but sometimes the fix is not local (may require looking at imported ontologies)

Jeremy Carroll: declaration is good style - RDF graphs are unordered - so declarations can be non-local

Michael Smith: searching for declarations require two passes - which can be expensive

Alan Ruttenberg: why not do typing "as seen"

Boris Motik: this requires deferring processing, and is hard

Bijan Parsia: in any case, there is a lot of extra work to make the RDF parsing go through

Jeremy Carroll: there are implementations that do good jobs

Bijan Parsia: no - there are bugs

Jeremy Carroll: but you do get benefits - use of RDF

Bijan Parsia: but there is a cost

Jeremy Carroll: multiple vocab is an attempt to fix this?

Bijan Parsia: yes

Alan Ruttenberg: compatibility means that there is no way out

Jeremy Carroll: Streaming OWL DL; ESWC 2004; JJ Carroll; LNCS 2004, ISSU 3053, pages 198-212
Jeremy Carroll: describes a streaming approach to OWL DL species validation
Jeremy Carroll: (but its hard)

Ian Horrocks: if we make a better way, then the old versions will die out (eventually)

Imports

Matthew Horridge: imports issues

Matthew Horridge: if //...foo.... imports //...bar... what does it mean?

Matthew Horridge: name of an ontology or a location of an ontology

Matthew Horridge: what if the name and the location don't match

Matthew Horridge: imports on OWL DL is controlled by OWL S&AS 3.4

Matthew Horridge: OWL reference says imports is by location

Matthew Horridge: OWL guide says something confusing

Matthew Horridge: want some direct and normative statement

Jeremy Carroll: section 5 OWL S&AS:
Jeremy Carroll: - Definition: Let T be the mapping from the abstract syntax to RDF graphs from Section 4.1. Let O be a collection of OWL DL ontologies and axioms and facts in abstract syntax form. O is said to be imports closed iff for any URI, u, in an imports directive in any ontology in O the RDF parsing of the document accessible on the Web at u results in T(K), where K is the ontology in O with name u.
Jeremy Carroll: (that definition is clear)

Matthew Horridge: solution was by name (essentially)

Matthew Horridge: what is the name of an ontology?

Matthew Horridge: guide is confusing

Matthew Horridge: test cases for OWL 1.0 were very useful - we need them for 1.1

Matthew Horridge: OWL 1.1 SS diagrams were useful

Jeremy Carroll: we need some time to talk about testing

Bijan Parsia: yes - infrastructure is needed

Jeremy Carroll: probably only need a short amount of time

Introductions (additions)

Alan Rector (guest from Manchester)

Ratnesh Sahay (DERI Galway)

Alan Ruttenberg

History (including OWLED)

Speaker - Bijan Parsia (no slides)

Bijan Parsia: OWLED - started in 2005 to let people interested in OWL design and use together

Bijan Parsia: there was about 1.5 years of experiece in OWL - there were complaints (particularly QCRs and datatypes)

OWL 1.1

Bijan Parsia: idea for a "bug fix" update to OWL - things that are relatively easy and wanted

Bijan Parsia: particularly wanted by users

Bijan Parsia: workshop was (largely) to discover what this new version would be

Bijan Parsia: workshop was adjacent to ISWC 2005 - about 60 participants

Michael Smith: mailing list archives for initial owled community http://lists.mindswap.org/pipermail/owl/
Michael Smith: workshop design summary first msg: http://lists.mindswap.org/pipermail/owl/2005-November/000001.html

Bijan Parsia: desiderata for changes:

Bijan Parsia: 1/ requested by major users

Bijan Parsia: 2/ have effective reasoning methods

Bijan Parsia: 3/ will be implemented

Bijan Parsia: (alternatively commitment from users, well understood, committment from implementers)

Bijan Parsia: other goals: quiet whining, promote apps, improve spec, move forward, path for extensions, reduce species confusion (particularly DL/Lite)

Bijan Parsia: example - move OWL-S to OWL DL

Bijan Parsia: tool feature - coercion to OWL DL in Pellet

Jeremy Carroll: tools *should* do this

Bijan Parsia: *mostly* get the right thing

Bijan Parsia: there are still things that people want to do - e.g., lists

Bijan Parsia: I implemented shadow lists -- RDF Lists with a parallel vocabulary, just a different namespace. Pellet can do this silently.

Jeremy Carroll: can rdf:list be fixed?

Bijan Parsia: issues of modelling lists (eg, breaking them) affecting syntax

Alan Ruttenberg: are lists necessary?

Bijan Parsia: yes

Peter Patel-Schneider: Lists are only in RDF because OWL-WG demanded them.

Peter Patel-Schneider: We needed them for the OWL syntax

Deborah McGuinness: consensus on what do to?

Bijan Parsia: no, just consensus on desiderata

Bijan Parsia: OWL 1.1 design is driven by the three main desiderata

Carsten Lutz: are all three needed?

Bijan Parsia: not in all cases, but in most cases

Stability vs Missing Features

Jeremy Carroll: some groups want stability

Bijan Parsia: main desiderata do lean towards stability

Ivan Herman: there is still a long process to use OWL, so change is bad

Jeremy Carroll: HP didn't participate in OWLED due to financial desires

Alan Rector: missing features in OWL have hindered uptake

Bijan Parsia: currently missing feature is keys

Ivan Herman: different markets - some want more features, some want no change

Peter Patel-Schneider: why?

Bijan Parsia: why should people who are only taking taking part of OWL care about OWL being extended?

Sandro Hawke: This is "OWL Pixie Dust". People want some of the OWL Magic, without really knowing what OWL is or does for them......

Alan Rector: standards all change so why is new OWL a problem?

Joanne Luciano: they might care if backwards compatability would break

Alan Rector: there are issues with backward compatibility

Alan Rector: Standards grow, with backward compatibility. And sometimes there are mistakes that need to be fixed.

Ian Horrocks: maintenance is needed

Deborah McGuinness: users want transition path and backwards compatibility

Joanne Luciano: and fixing mistakes or updating costs.
Joanne Luciano: updating has costs associated with it is what I meant to say

Ivan Herman: we need to take care of stability concerns

Bijan Parsia: model of development - do lots of work outside W3C, then quick recommendation, repeat roughly yearly

Ivan Herman: stability - vague uneasiness (mostly)

Alan Ruttenberg: what can we do to help?

Ivan Herman: nothing, really

Sandro Hawke: if the perception is that OWL 1.0 is broken then that is even worse than the perception that things are unstable because we're working on 1.1

Jeremy Carroll: Bijan quoted DannyAyers "Don't hurt the triples"

Alan Rector: for me OWL 1.0 is not usable - so I need OWL 1.1

Bijan Parsia: look for people who have real blockage and try to help them

Effect of OWLED

Bijan Parsia: Bijan: OWLED attendance and submissions have been growing

Bijan Parsia: many participants felt that OWLED gave them a voice

Bijan Parsia: OWLED experience has been positive

Bijan Parsia: testimonial from Kent Spackman (SNOMED person)

Sandro Hawke: adjourn for coffee