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Re: Pointers model

From: Shadi Abou-Zahra <shadi@w3.org>
Date: Wed, 19 Sep 2007 16:05:35 +0200
Message-ID: <46F12CAF.4020109@w3.org>
To: Carlos Iglesias <carlos.iglesias@fundacionctic.org>
CC: public-wai-ert@w3.org

Carlos Iglesias wrote:
>> This solution is far from optimal in my opinion. What if I want to
>> introduce a new XYZOffsetPointer? Since it is easy to do a query like
>> ("offsetNode" rdf:type ?) and find out what kind of a pointer type it
>> is, I don't think it is a good idea to be that restrictive.
> 
> 
> I'm afraid that I'm not following you here. Could you elaborate please? 

One can tell the type of pointer without needing an explicit class. For 
example this piece of code:

<ptr:StartOffsetPointer ...>
   <ptr:offset rdf:resource="#offset" />
   ...
</ptr:StartOffsetPointer>

<ptr:CharOffsetPointer rdf:about="offset">
   ...
</ptr:CharOffsetPointer>


This will also have the following N3 serialization:

...
("offset" rdf:type ptr:CharOffsetPointer)
...

So it is quite easy to get the information and there is no need to 
create an explicit class for it.


> Also note that we're already been that restrictive with OffsetPointers (CharOffsetPointer and ByteOffsetPointer)

Yes, because from OffsetPointer alone one cannot tell what value will be 
inside the offset. Another approach could have been:

OffsetPointer (ptr:offset, ptr:type)

Where "ptr:type" would define if the offset is a byte or char. There are 
other solutions too, but we happen to have selected that one. It is a 
different situation to the compound pointers though...


Regards,
   Shadi


-- 
Shadi Abou-Zahra     Web Accessibility Specialist for Europe |
Chair & Staff Contact for the Evaluation and Repair Tools WG |
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Received on Wednesday, 19 September 2007 14:05:41 GMT

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