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RE: Validation in CC/PP

From: <franklin.reynolds@nokia.com>
Date: Thu, 6 Jun 2002 11:41:07 -0400
Message-ID: <E320A8529CF07E4C967ECC2F380B0CF906E3BD@bsebe001.NOE.Nokia.com>
To: <Mark_Butler@hplb.hpl.hp.com>, <w3c-ccpp-wg@w3.org>, <www-mobile@w3.org>

I am not opposed to the idea of making automatic validation 
possible, but I am not convinced it is important topic for the 
working group. Validation will not catch all profile errors or
even all property name errors. Ultimately vendors have to 
inspect and test their profiles. 

Having said that,
I thought the current vocabulary guidelines said that all CC/PP
properties should be derived from CC/PP types? What more do we
need to add to the spec to enable a validation program to catch
possible "PixelsAspectRatio not PixelAspectRatio" bugs?

I appreciate the problem of verifying the type/format of RDF literal
values, but I am reluctant to commit CC/PP to solving this problem
ahead of the RDF community. Unless we know the RDF standards group
isn't going to solve this problem, I think we should avoid 
inventing our own solution.

I don't know anything about DAML. Their strategy for using 
XML Schemas might do the job, but I would be uncomfortable adopting
this before the RDF Core or similar working group blessed the 
approach.

Franklin

> -----Original Message-----
> From: ext Butler, Mark [mailto:Mark_Butler@hplb.hpl.hp.com]
> Sent: Wednesday, June 05, 2002 12:40 PM
> To: 'w3c-ccpp-wg@w3.org'; 'www-mobile@w3.org'
> Subject: Validation in CC/PP
> 
> 
> 
> In my opinion, one key problem with CC/PP as it currently 
> stands is there is
> no notion of profile validation. I've been speaking about 
> this to people
> here at HP working on RDF and they have made a number of 
> suggestions. I'd
> like to briefly outline these suggestions as I think they are 
> of general
> interest to people working on CC/PP. 
> 
> So why do we need validation? Well experience with existing CC/PP
> vocabularies has shown that even with a small number of 
> profiles, vendors
> make mistakes when creating profiles. For example they get 
> property names
> wrong e.g. use PixelsAspectRatio not PixelAspectRatio. There 
> is also no
> agreement on property literal values so two vendors might use the same
> literal to indicate different capabilities or different 
> literals to indicate
> the same capability e.g. "1.2.1/June 2000" and "1.2.1" are 
> used to refer to
> the same capability. 
> 
> My colleague Andy Seaborne has suggested there are three 
> assumptions you can
> make about RDF properties when performing schema validation 
> in order to
> solve the first problem:
>  
> i) Open - the "correct" validation of data against a schema - 
> can never
> actually say anything is wrong because RDFS does not make any 
> closed world
> assumptions or contain negation. 
> ii) Strict - must be able to prove that a resource is the 
> type specified,
> whether by domain/range or by rdf:type declaration.
> iii) Exact - the resources must have all and only the 
> declared properties.
> This is a crude way of getting a robust checking - really 
> need the idea of
> optional/mandatory properties.
> 
> So it seems to me that by default CC/PP should be using the Strict
> assumption i.e. a property can only be used in a profile if 
> it is defined in
> the associated schema. In addition if a property is associated with a
> component(s), then it can only appear there. In the future, 
> we may have
> vocabularies where a device must supply all the profile attributes to
> conform to the vocabulary i.e. schema need to be able to 
> define if they
> should be interpreted as Exact. 
> 
> The second problem has also been encountered by the DAML 
> community who have
> explored using XML Schema (XSD) to perform data validation on literal
> values. For example this validator
> http://www.daml.org/validator/
> provides support for XML schema validation using the Oracle 
> XDK XML Schema
> Validation toolkit to verify DAML files.
> 
> For examples of how to reference XSD in RDF, see this DAML example
> http://www.daml.org/validator/examples/dt4.daml
> which uses this XML schema file
> http://www.daml.org/validator/examples/dt1.xsd
> via the dt namespace prefix i.e. 
> 
> <rdf:RDF 
> xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" 
> xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#" 
> xmlns:daml="http://www.daml.org/2001/03/daml+oil#" 
> xmlns:xsd="http://www.w3.org/2000/10/XMLSchema#" 
> xmlns:dt="http://www.daml.org/validator/examples/dt1.xsd#">
> 
> I also found this document, Annotated DAML+OIL, useful
> http://www.daml.org/2001/03/daml+oil-walkthru.html
> 
> So what do other people think about this? Would providing 
> validation be
> useful? Are there any other appropriate methods?
> 
> best regards
> 
> Mark H. Butler, PhD
> Research Scientist                HP Labs Bristol
> mark-h_butler@hp.com
> Internet: http://www-uk.hpl.hp.com/people/marbut/
> 
> 
Received on Thursday, 6 June 2002 11:41:15 GMT

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