Re: Recursion in RDF Data Shape Languages

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This is an entirely new approach.  It builds on none of the proposals in the
working group and does not appear to be compatible with any of them.  It is
certainly not a fixed-up version of the Z-based semantics in the Shape
Expressions member submission.  The approach builds up a minimal set of
labellings, which is different from Iovka's approach and from Jose's

In the approach it is not possible to require that some neighbour has a
constraint, only that all of them do.

The interface to the approach starts with a node and a shape for that node
and determines whether that node can belong to the shape.  There are no
options to start with multiple nodes and shapes, or any of the other options
in the various approaches, such as scoped shapes.

The approach has a very large number of moving parts, with neighbour
functions, constraints, shapes, data graphs, neighbour graphs, labelled
graphs, and constrained graphs.  This seems to me to be too much machinery
for the task at hand.

I do not understand why the PIM application "enforces" a particular
constrained graph.  Surely that is what is supposed to be determined by the
approach, not what is input to the approach.

This document provides a particularly bad support for recursive definitions
because the running example can be easily handled without recourse to
recursive definitions, via
1/ there is a node that has type foaf:Person and exactly one foaf:name
2/ all the foaf:knows edges from the contact terminate at nodes
  - that have type foaf:Person, and
  - have only one incoming foaf:knows link.
The exposition of the running example permits graphs where the contact is
the associate.

The document uses "unique name" where it could be misread to mean that name
is a key.

SPARQL 1.1 path expressions are much more general than path expressions,
which appear to be just properties and inverses.  A different name should be


On 05/20/2015 05:35 AM, Arthur Ryman wrote:
> I just posted an article that formalizes the kind of recursion that 
> Resource Shape 2.0 supports. [1] It therefore also covers a subset of the
> kind of recursion that SHACL(Holger) and SHACL(ShEx) supports. I believe
> this kind of recursion could be added to SHACL-SPARQL(Peter).
> The article is language-neutral in the sense that it does restrict how 
> constraints are specified. It uses Z Notation, but I've attempted to keep
> it as simple as possible, and I've illustrated every definition with a
> running example.
> In the interest of having a stable version, I've posted it on arXiv. I'd
> appreciate feedback and will include corrections or improvements in the
> next version. Thanks.
> [1]
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Received on Thursday, 21 May 2015 01:44:43 UTC