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Re: cannonical ordering in the XML

From: Bijan Parsia <bparsia@cs.man.ac.uk>
Date: Thu, 13 Sep 2007 11:34:04 +0100
Message-Id: <46FE78B0-36D3-4622-99ED-DE65B311BF95@cs.man.ac.uk>
To: Owl Dev <public-owl-dev@w3.org>

On 13 Sep 2007, at 11:17, Matthew Horridge wrote:

> Hi Matthew,
>> The spec for owl 1.1 defines equality over expressions. However, I  
>> can't see
>> where it defines ordering over expressions. The haskell code I've  
>> got does
>> provide a total ordering over all bits of the owl 1.1 syntax,  
>> meaning that I
>> always process/serialize statements in a consistent order.

This is great.

>> This is
>> particularly important in the xml serialization, particularly if  
>> we wish to
>> be able to do diffs.

It's super important in general.

>> Have I missed the bit that talks about cannonical orderings? Is  
>> there an
>> expected (although not required) order in which we should  
>> serialize elements
>> to xml?

No though one could emerge and tools could converge.

> I don't think there is such a document.

There isn't. There's actually two or three places it could go: e.g.,   
In the functional syntax document or in the XML syntax document. Or  
in a canonicalization document.

> Would you be able to document your approach and post it to the  
> list?  (I could then add this to the OWL API, which already has an  
> axiom comparator, but it would be great if there was a more  
> standard approach).

Indeed. The approach currently taken in the structural spec is a bit  
"abstract" with regard to concrete documents in that it uses sets  
quite a bit (e.g., an ontology is a set of axioms). I think being a  
bit more specific on parsing, comparison of parses, and serialization  
is a good thing for the WG to do. Any first steps toward this are  
more than welcome.

Received on Thursday, 13 September 2007 10:32:54 UTC

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