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Re: is there an implementation of Shape Expressions that correctly handles recursive shapes?

From: Eric Prud'hommeaux <eric@w3.org>
Date: Wed, 25 Mar 2015 03:02:50 -0400
To: "Peter F. Patel-Schneider" <pfpschneider@gmail.com>
Cc: RDF Data Shapes Working Group <public-data-shapes-wg@w3.org>
Message-ID: <20150325070248.GA9805@w3.org>
* Peter F. Patel-Schneider <pfpschneider@gmail.com> [2015-03-24 15:28-0700]
> I don't think that the fix is to add extra explanation here.
> 
> Based on my analyses, the problem is with two of the three formal
> specification of Shape Expressions. Any implementation of either of these
> two specifications is going to be problematic. Based on a bit of testing it
> appears that the Fancy ShEx Demo is based on an implementation of the
> axiomatic semantics.

If the goal is to match the users' expectations, I would expect that
exploring all possible models would do that. For instance, if we say
  ex:b matches <T> iff ex:c fails <T>
  ex:c matches <T> iff ex:b fails <T>
, we've covered the possible solutions. An alternative is to say that
  ex:b matches <T>
  ex:c matches <T>
because they don't pass in all models. By tracking the node/shape pairs
involved in a particular solution, I think we can cheaply explore the
permutations of A iff !B. If this doesn't appeal, what do you propose
is a good answer to your dilema?


> I'm looking at the system that Iovka sent me, as it appears to be based on
> the third formal specification of Shape Expressions, but it appears that
> that system uses some syntax other than the Shape Expressions syntax as
> defined in the W3C Submission.

I think it's useful to give users the ability to see what parts of the
graph weren't covered by the graph


> peter
> 
> 
> On 03/24/2015 03:10 PM, Eric Prud'hommeaux wrote:
> > * Peter F. Patel-Schneider <pfpschneider@gmail.com> [2015-03-22 
> > 10:37-0700]
> >> That's working better now.  At least we are getting to the Shape 
> >> Expressions problems.
> >> 
> >> I have attached two screen shots showing different behaviour on the 
> >> same graph.
> > 
> > I've added a bit to note inconsistencies between different models. I 
> > don't know of a real answer to a two-party liars' paradox, but you may 
> > find the disclosures more revealing and consistent.
> > 
> > http://www.w3.org/2013/ShEx/FancyShExDemo?starting-nodes=ex%3Ab%20ex%3Ac&sch
> ema=PREFIX%20ex%3A%20%3Chttp%3A%2F%2Fex.example%2F%23%3E%0Astart%3D%3CT%3E%0A%
> 3CT%3E%20%7B%20ex%3Aq%20.%20%7C%20ex%3Ar%20%40%3CT%3E%20%7D%0A&data=PREFIX%20e
> x%3A%20%3Chttp%3A%2F%2Fex.example%2F%23%3E%0Aex%3Ab%20ex%3Aq%20ex%3Az%20.%0Aex
> %3Ab%20ex%3Ar%20ex%3Ac%20.%0Aex%3Ac%20ex%3Aq%20ex%3Az%20.%0Aex%3Ac%20ex%3Ar%20
> ex%3Ab%20.&colorize=true
> >
> >
> > 
> BTW, since the browser-dependent bugs appear to have subsided, you
> > probably only need to send me a permalinks.
> > 
> > 
> >> peter
> > 
> > 
> > 
> > 

-- 
-ericP

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Received on Wednesday, 25 March 2015 07:02:53 UTC

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