- From: Peter F. Patel-Schneider <pfpschneider@gmail.com>
- Date: Wed, 01 Jul 2015 09:32:58 -0700
- To: Arthur Ryman <arthur.ryman@gmail.com>, "public-data-shapes-wg@w3.org" <public-data-shapes-wg@w3.org>
The semantics in http://w3c.github.io/data-shapes/semantics has an unusual treatment of negation. You should think of the semantics as providing partial interpretations for the shapes. However, certain shapes need a full interpretation so that negation can be handled. Which shapes need to be so treated? The shapes in negshapes(S). The definition of negshapes(S) is thus not directly related to negated shapes in S but is instead "those shapes that need a full intepretation". Are the definitions in the document adequate? I certainly don't know. Is the resultant semantics reasonable? I don't think so - see earlier posts. Can the resultant semantics be effectively computed? Probably not, as the check for a valid typing could involve looking at very many other typings. peter PS: It appears to me that the semantics as written allows for valid typings where both s and !s are on the label of some node in G. It may be that the way to fix this is to tighten the definition of typing. On 07/01/2015 07:33 AM, Arthur Ryman wrote: > Iovka/Eric, > > The semantics document [1] contains this clause in the definition of > negshapes(S): > > * there is a shape label T1 and a shape triple constraint p::C, or an > inverse shape triple constraints ^p::C in expr(T1, S), and T appears in > C. > > This looks wrong since there is no negation involved. Is this clause > correct? If so, please explain the reason for this definition. Thanks. > > BTW, I am working with the June 22 version, but I see that the latest is > June 30. What are you changing? I'd appreciate revision bars and > history. > > [1] http://w3c.github.io/data-shapes/semantics/#semantics_preliminaries > > -- Arthur >
Received on Wednesday, 1 July 2015 16:33:30 UTC