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Suggestion: Constructing Containers/Collections

From: Leigh Dodds <leigh.dodds@talis.com>
Date: Fri, 6 Mar 2009 10:28:51 +0000
Message-ID: <f323a4470903060228w43027997t3e0cd3afa89c20ce@mail.gmail.com>
To: public-rdf-dawg-comments@w3.org
Hi,

I have the following feature suggestion for the WG.

Feature: Ability to Construct a List or Collection

Feature Description:

  At present it is not possible to construct or reconstruct an
rdf:List or an RDF container of an
  arbitrary size in a SPARQL CONSTRUCT query. This means that
CONSTRUCT cannot be used to
  reconstruct some data that exists in the graph, nor can it be used
to create some legal forms of
  RDF.

  A DESCRIBE query is only a viable alternative only if the
collection/container is a bnode and the default
  algorithm generates a bounded description that includes the list
contents. But even then not all of
  the desired context (e.g. properties of the list members) would be included.

Example

 Don't have a concrete example of this in practice. It may be that a
combination of assignment to a
 variable (to create the container or collection resource), and then
application of a property function
 similar to that implemented in ARQ would enable this.

Existing  Implementations

  None that I'm aware of. ARQ's property functions only cover
iteration/access over members of the
  container/collection not construction.

Use Cases

  Remove the current restrictions on being able to CONSTRUCT RDF
Container/Collections.

  The primary example of where this was an issue was with working with
a bibliographic dataset in which
  the Table of Contents for an issue of a journal or a book was
modelled as an RDF List (i.e. as an ordered
  collection with a fixed membership). It was not possible to write
CONSTRUCT queries to extract the information
  required to present a user interface showing all the desired data.
The work around was to use a CONSTRUCT
  with ARQ list extensions to get the core data, a SELECT query and
custom code to reconstitute the structure
  of the original list, and then a merge of the data graphs. Support
for list construction in the query language
  would avoid the need for the extra code and queries.

Cheers,

L.

-- 
Leigh Dodds
Programme Manager, Talis Platform
Talis
leigh.dodds@talis.com
http://www.talis.com
Received on Friday, 6 March 2009 10:29:31 GMT

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