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Re: Structure of Evidence class

From: Shadi Abou-Zahra <shadi@w3.org>
Date: Mon, 03 Oct 2005 16:10:10 +0200
Message-ID: <43413BC2.2060000@w3.org>
To: Charles McCathieNevile <chaals@opera.com>
Cc: public-wai-ert@w3.org

Hi Charles,

I agree with you on the closure problem of the evidence collection. However, isn't this a general issue we should address in EARL anyway? I mean, one could just as well add a dc:hasPart or even an (additional) earl:testcase to an existing assertion and thus change the whole meaning of it. It seems we will need an EARL-wide policy of how to treat "original" assertions and modifications of these done through annotation.


Charles McCathieNevile wrote:
> On Wed, 28 Sep 2005 17:11:31 +0200, Shadi Abou-Zahra <shadi@w3.org> wrote:
>> Right now the proposal for earl:evidence suggests the class to be a  
>> collection of assertions. This will make queries (for example to 
>> compare  if two evidence clauses are equal) difficult because the 
>> order of the  assertions defines the actual RDF graph.
> ...
> Right. You have to query whether things are in the list, and there is 
> no  direct support for that in SPARQL, so you have to get the list, and  
> traverse it checking for the thing you want.
>> Another approach is to define a property with range earl:evidence and  
>> domain earl:assertion. This property will describe a relationship  
>> between the evidence and the sub-assertions. Here is an example:
> Minor correction - you have to make a class that has the properties, 
> since  evidence is meant to be a property of either assertion or result. 
> The  easiest way is to use a blank node, although it would make sense to 
> define  a class for evidence. So you would have
>> <earl:evidence r:parseType="Resource">
>>   <earl:hasAssertion rdf:resource="someAssertion"/>
>>   <earl:hasAssertion rdf:resource="anotherAssertion"/>
>>   ...
>> </earl:evidence>
> or you could have (incorporating the idea below of having both 
> structures  - we could select one or the other)
> <e:Assertio>
>   ...
>   <e:evidence>
>     <e:EvCollection r:ID="someID">
>       <e:fullEvidenceList rdf:parseType="Collection">
>          [each assertion]
>       </e:fullEvidenceList" />
>       <e:hasAssertion r:resource="someAssertion"/>
>       <e:hasAssertion r:resource="otherAssertion"/>
>       <e:hasAssertion r:resource="moreAssertion"/>
>  etc
> ...
>> What do you think of this approach?
> The problem with it is that due to the open world nature of RDF, people  
> can add a statement to your claim. A collection is, I am pretty sure, 
> the  only RDF construct where there is no way to extend it without 
> throwing up  an error.
> One way to solve the problem is to require that there are both 
> structures.  This seems like bloating the format in favour of simpler 
> processing of a  query. It should not be technically difficult to 
> implement. I think an  evidence statement is an atomic thing - once you 
> have made an inference  its conclusions should not be altered. So if you 
> change your mind you make  a new assertion, rather than changing the old 
> one.
> cheers
> Chaals

Shadi Abou-Zahra,     Web Accessibility Specialist for Europe 
Chair and Team Contact for the Evaluation and Repair Tools WG 
World Wide Web Consortium (W3C),           http://www.w3.org/ 
Web Accessibility Initiative (WAI),    http://www.w3.org/WAI/ 
WAI-TIES Project,                 http://www.w3.org/WAI/TIES/ 
Evaluation and Repair Tools WG,     http://www.w3.org/WAI/ER/ 
2004, Route des Lucioles -- 06560, Sophia-Antipolis -- France 
Voice: +33(0)4 92 38 50 64           Fax: +33(0)4 92 38 78 22 
Received on Monday, 3 October 2005 14:10:12 UTC

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