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Owl 1.1 DL and OWL 1.1 Full

From: Jim Hendler <hendler@cs.rpi.edu>
Date: Wed, 7 Nov 2007 09:01:52 -0500
Message-Id: <71BD4AB0-1149-4F4A-A447-65C1ACDF9478@cs.rpi.edu>
Cc: Jeremy Carroll <jjc@hpl.hp.com>, Sandro Hawke <sandro@w3.org>
To: OWL Working Group WG <public-owl-wg@w3.org>

I was thinking about whether this should be an actual issue or not,  
but decided to start it here - Depending how I interpret the current  
documents I can see this being anything from a null issue to a real  
re-chartering need, so I thought I better bring it up...

  if you look at the OWL Requirements and Use Cases [1], you will see  
that "Effective Decision Procedure" (define as decidability) is an  
Objective of the language, not a requirement.  We may all have  
somewhat different memories of how we got to that, but basically,  
there was not consensus in the group at that point in time that every  
feature we would want in a Web Ontology Language would be decidable.
  As it turned out, this came to be important, and the case that  
really brought it to the fore was the issue of inverseFunctional  
datatypes.  To make a long story short, the discussions around this  
issue almost scuttled the Working Group (I was on the phone with the  
W3C director several times to convince him to let us try to find a  
way around the impasse), and it was a compromise (brokered by Frank  
van Harmelen) which led to us having a restricted subset of the  
language, later called OWL DL, and an unrestricted one, which came to  
be called OWL Full.
  This distinction is not artificial - the issues that couldn't be  
resolved at that time, and some still can't, cause the split between  
the two branches of OWL, and there are clearly those on the AC,  
including myself (since i'm not chair and can have an opinion this  
time), who need and care about OWL Full.

OK, now to the present - In the OWL 1.1 Web Ontology Language  
Submission [2], the background makes it very clear that OWL 1.1 arose  
because "an extension of OWL-DL was proposed."  And, in fact, it  
turns out that the documents for OWL 1.1 do indeed include an  
extension to OWL DL, but it is unclear, and a real issue, as to how  
they treat OWL full.  For example, in the BNF for OWL 1.1, the  
following is included:

inverseFunctionalObjectProperty := 'InverseFunctionalObjectProperty'  
'(' { annotation } objectPropertyExpression ')

but I can find no similar construct for  
inverseFunctionalDatatypeProperty - so in essence the OWL Full  
construct has been ignored completely.

This could be simple to deal with - these omissions can be easily  
fixed when a section on OWL 1.1 Full is added to the document
This could be a charter issue - since it very clearly contradicts the  
charter [3] statement that

"All new features should have a clear syntax, and a clear semantics  
both in terms of OWL DL and OWL Full. The existing compatibility  
between OWL DL and OWL Full should be preserved, and should be  
extended to new features wherever possible."

So, I'm hoping this will be explained as my misunderstanding of the  
new documents (which I admit I'm still having trouble working out the  
details of) and not a real issue.  If I'm right, then I am afraid  
I'll need to oppose publication of the OWL 1.1 documents until  
something about this is added somewhere, since I think it would be a  
mistake for the WG to publish working drafts that are in violation of  
our charter

p.s. Please note I only discussed inversefunctionaldatatype, but the  
same goes for all the differentiators of Full vs. DL - and also for  
new features, cf. my email about Issue 8 which falls under extending  
OWL Full in the new feature (i.e. allowing a property chain to end in  
a datatype property should clearly be allowed in OWL 1.1 Full)

p.p.s. Lest anyone mistake me - I am not claiming this is currently a  
charter violation, that would be a big step I'm not ready to take,  
rather I'm asking for clarity on this and on whether it is something  
the WG needs to take into consideration.

[1] http://www.w3.org/TR/webont-req/
[2] http://www.webont.org/owl/1.1/
[3] http://www.w3.org/2007/06/OWLCharter.html  (may be member  
readable only, I forget if charters are public)
Received on Wednesday, 7 November 2007 14:04:37 UTC

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