Re: recursive shapes in shape expressions

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Just a preliminary response to get at a particular part of one example.

On 02/23/2015 07:25 AM, Iovka Boneva wrote:

> 
> Le sam. 21 févr. 2015 23:27:52 CET, Peter F. Patel-Schneider a écrit :
>> 

[...]
> 
>> There are ever trickier situations involving recursive shapes. For
>> example, consider the two mutually recursive shapes <S> { ( ex:p @<S> |
>> ex:p @<T> ) } <T> { ( ex:p @<T> | ex:p @<S> ) } (something is in <S> if
>> it has an ex:p fillers and either all its ex:p fillers are in <S> or
>> its ex:p fillers are in <T> but not both, and similarly for <T>). It is
>> unclear as to which nodes should have shape <S> or <T> in the graph 
>> ex:a ex:p ex:b . ex:b ex:p ex:a .
>> 
> 
> With our semantics and considering /closed/ shapes, the shape
> 
> <S> { ( ex:p @<S> | ex:p @<T> ) }
> 
> intuitively says that a <S> typed node should have exactly one outgoing
> ex:p, that leads either to <S> or to <T> node. This however does not
> forbid the target node to have both <S> and <T>; we exclude any form of
> negative constraints.
> 
> There are 9 valid typings, associating with ex:a and ex:b, in this order,
> the sets of shapes: {<S>} {<S>} {<S>} {<T>} {<S>} {<S>,<T>} {<T>} {<S>} 
> {<T>} {<T>} etc. actually all combinations in the Cartesian product {
> {<S>}, {<T>}, {<S>,<T>} } X { {<S>}, {<T>}, {<S>,<T>} } The unique
> maximal typing is <S>,<T> for both ex:a and ex:b.

Huh?

If ex:b is of type {<S>,<T>} then <ex:a> should not be <S> or in <T> because
both arms of the exclusive or disjunct are true.  The literature that I have
read on shape expressions is very clear that exclusive or is the meaning of
the | construct - see
http://www.w3.org/Submission/2014/SUBM-shex-primer-20140602/ for example.

Are you saying instead that the meanings of the fundamental constructs in
shape expressions vary between different accounts?


peter

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Received on Tuesday, 24 February 2015 01:02:32 UTC