- From: Yosi Scharf <syosi@MIT.EDU>
- Date: Wed, 10 Aug 2005 14:47:08 -0400
- To: public-cwm-talk@w3.org
- CC: syosi@MIT.EDU
Cwm can now has support for being a SPARQL server. To learn more about
SPARQL, see http://www.w3.org/TR/rdf-sparql-query/
There are several pieces to this support.
(1) http://www.w3.org/2000/10/swap/grammar/sparql is a machine readable
grammar for sparql.
(2) in the http://www.w3.org/2000/10/swap/sparql/ directory there is
sparql_parser.py, which uses a LL(1) table generated from sparql.n3 to
generate a parse tree.
(3) http://www.w3.org/2000/10/swap/sparql2cwm.py which compiles the
SPARQL into n3.
Actually looking at what is generated is fascinating in my opinion, but
far from necessary [1].
(4) builtins used in the converted n3. These are defined in
http://www.w3.org/2000/10/swap/sparqlCwm , and implemented in
http://www.w3.org/2000/10/swap/cwm_sparql.py.
(5) Modifications to the cwm query engine to support sparql's error
handling. --mode=q enables these if you are not doing a SPARQL query.
(6) command line arguments for using sparql. --sparql= is usable in the
same way as --query= . Also, --language=sparql tells cwm that the
following file is sparql.
(7) builtins for using cwm's SPARQL support from within n3. These are
also defined at http://www.w3.org/2000/10/swap/sparqlCwm , and
implemented in http://www.w3.org/2000/10/swap/cwm_sparql.py .
(8) Fixes to cwm's xml output class to allow for the outputting of the
SPARQL results format.
(9) A (experimental) Cwm sparql server. if cwm sees --sparqlServer on
the command line, at that point in processing it stops and starts an
http server on port 8000. I have one of these running for now at
mr-burns.w3.org:8000 (no guarentees about how long that will stay up).
Tests for cwm's SPARQL support are listed in
http://www.w3.org/2000/10/swap/test/sparql/detailed.tests .
Known Limitations:
- Cwm does not support result ordering or limiting at this time. If you
specify an order of the results or a limit, cwm with throw a
NotImplementedError.
- The order of the variables given in a SELECT query is not preserved.
- DESCRIBE queries are not supported.
- Some queries involving lists [2] will fail.
Yosi
--------------------------------------------
[1] here is a simple example of the transformation:
syosi@mr-burns:~/CVS-local/WWW/2000/10/swap/test/sparql$ cat test1.sparql
PREFIX foaf: <http://xmlns.com/foaf/0.1/>
SELECT ?mbox
WHERE
{ ?x foaf:name "Johnny Lee Outlaw" .
?x foaf:mbox ?mbox }
syosi@mr-burns:~/CVS-local/WWW/2000/10/swap/test/sparql$ cwm
--language=sparql test1.sparql
#Processed by Id: cwm.py,v 1.176 2005/08/10 17:03:22 syosi Exp
# using base
file:/home/syosi/CVS-local/WWW/2000/10/swap/test/sparql/test1.sparql
loaded from file 1.59013986588
# Notation3 generation by
# notation3.py,v 1.180 2005/06/09 21:05:14 syosi Exp
# Base was:
file:/home/syosi/CVS-local/WWW/2000/10/swap/test/sparql/test1.sparql
@prefix : <http://yosi.us/sparql#> .
@prefix log: <http://www.w3.org/2000/10/swap/log#> .
@prefix spa: <http://www.w3.org/2000/10/swap/sparqlCwm#> .
@prefix test: <#> .
@forAll :mbox,
:x.
@forSome test:_g0 .
"file:/home/syosi/CVS-local/WWW/2000/10/swap/test/sparql/"
spa:data test:_g0 .
[ a spa:SelectQuery;
spa:select {:mbox spa:bound "mbox" .
};
spa:where {test:_g0 log:includes {:x
<http://xmlns.com/foaf/0.1/mbox> :mbox;
<http://xmlns.com/foaf/0.1/name> "Johnny Lee Outlaw" .
} .
} ].
{
test:_g0 log:includes {:x
<http://xmlns.com/foaf/0.1/mbox> :mbox;
<http://xmlns.com/foaf/0.1/name> "Johnny Lee Outlaw" .
} .
} log:implies {{
:mbox spa:bound "mbox" .
} a spa:Result .
} .
#ENDS
[2] For instance:
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX : <http://example.com/here#>
SELECT *
WHERE {?x rdf:first :first }
cwm assumes all graphs contain all lists, so it cowardly refuses to give
infinite answers.
Received on Wednesday, 10 August 2005 18:47:22 UTC