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RE: Another attempt at 'cascading DRs'

From: Scheppe, Kai-Dietrich <k.scheppe@telekom.de>
Date: Thu, 14 Feb 2008 10:12:21 +0100
Message-ID: <398533C370C23441981074C456AA3BDD031DAEF9@QEO00226.de.t-online.corp>
To: "Andrea Perego" <andrea.perego@uninsubria.it>, "Public POWDER" <public-powderwg@w3.org>

Andrea,

I think I agree with you :-), because I think you concluded with what I
meant.


> In theory, we can (operationally) enforce a mechanism able to 
> determine whether a DR scope S1 is more *specific* than 
> another DR scope S2 wrt a given resource. For this purpose, 
> we have just to check whether the set of URIs denoted by the 
> regex corresponding S1 includes the set of URIs denoted by 
> the regex corresponding to S2. Which is exactly what you said, Kai.

Correct.  I suggest to use this an indicator or importance (which what
cardinality means in this context, right?).

<snip>

> Provided that, if we require that we cannot associate with a 
> resource more than one descriptor concerning property, e.g., 
> childSafe, this can be done by stating this restriction in 
> the RDF/OWL schema defining such property. Done that, if we 
> have two DRs saying:
> 
> DR1: example.org     -> childSafe=true
> DR2: example.org/foo -> childSafe=false
> 
> we decide the prevailing one based on the specificity of the 
> scope definition wrt to the resource's URI.

Correct, see above.

> 
> Note that this solution requires to check the definition of 
> property childSafe in the corresponding RDF schema. 
> Operatively this means:
> 
> 1. Retrieve the RDF/OWL schema defining childSafe 2. If 
> there's no restriction on the cardinality of childSafe, both 
> descriptors apply; otherwise, 3. If the scope definition of 
> one of the DRs is more specific than the other wrt the 
> resource's URI, the former overrides the latter; otherwise, 
> 4. If the two scope definitions are equivalent/incomparable... what? 
> (ignore both descriptors?)

I think you have described it quite well.
Using the specificity of the URI we can determine which descriptor
applies more.

You bring up an interesting point with 4.
I would suggest if the scope is equal, it is recognized that both
apply...somewhere within the scope.
That is not a bad thing.  All it says that we are lacking knowledge, at
that instance of precicely /*where*/ the differences occur.
This may lead to resource retrieval or not, depending on the context in
which the user is at that moment.

If, for example, the descriptors that there is childsafe content and
childunsafe content, a mother may have set her FOSI client to block the
entire scope.
Alternatively, if the descriptors say that some of the T-shirts for sale
are blue and some a red, the potential shopper will still retrieve
resources within that scope.


> An alternative to default overriding, is to specify explicit 
> overriding rules. But also in this case we have to check 
> whether two descriptors are in conflict or not, based on 
> their definition.

I am not sure we need that, because in the end we only want to provide
information.  
I don't think we should make decisions on what is desired and what not.

-- Kai
Received on Thursday, 14 February 2008 09:12:36 GMT

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