[redland-dev] ANN/RFC: SPARQL Query Tool

[Dave Beckett]

On Wed, 2 Mar 2005, Sebastian Dietzold wrote:
> Hi All, i've created a little php SPARQL Query Tool.
> 
> UseIt:  http://sebastian.dietzold.de/archive/2005/03/02/sparqlTool.php
> Source: http://sebastian.dietzold.de/archive/2005/03/02/sparqlTool.phps
> 
> --- From http://sebastian.dietzold.de/blog/2005/03/02/sparqltool ---

nice.
 
> I've played around with Redland and php because i need some small scripts 
> to modify rdf-models in a mysql db. First i wanted a tool to query an 
> existing model for debugging. Dave Becketts demo works fine but has no 
> options to query models in a mysql db. After two days of looking inside 
> the error.log of my apache (actual, many redland-errors will only appear 
> there and not in the html-output, because some functions are not 
> implemented in the php-module yet), i can release the first version of the 
> SPARQL Query Tool.

Yes, the structured error information is currently only available from C#, 
Perl and Python (in redland bindings 1.0.0.2).  It is best done as C 
functions helping SWIG as it can be quite low level generating exceptions.
 
> With this script, you can query models from urls or mysql dbs with SPARQL. 
> Actual, only variable binding results are supported (no graph or bool 
> results). I also plan to add a file upload feature. In the next version i 
> want a better handling with errors and warnings.

Boolean's quite easy :)

> To use this script with your own server, you need version 1.0.0.1 of the 
> redland php bindings. The whole script ist only one file so it is easy to 
> install. I think, it is a good demonstation example for the redland php 
> bindings.

Thanks

I should make the source of the http://librdf.org/query demo public as it 
shows how to get the error reports back in perl at least.  Basically it's 
like:

my $handler=sub {
  my($code, $level, $facility, $message, $line, $column, $byte, $file, $uri)=@_;
  if($level < 4) {
    push(@warnings, [$message, $line]);
  } else {
    push(@errors, [$message, $line]);
  }
  ...
}

RDF::Redland::set_log_handler($handler);

then later, if something fails, eg building a query:
  eval '$query=new RDF::Redland::Query($query_string, $base_uri, undef, $query_language);';
  if($@ || @errors || !$query) {
    my $err=join("<br />", map {$_->[1].":".$_->[0]} @errors);

    ... print out the error ...
    exit 0;
  }

Warnings are checked elsewhere in a similar fashion, but they are not 
fatal.

Dave