NAME
RDF::Query::Client - get data from W3C SPARQL Protocol 1.0 servers
VERSION
0.103
SYNOPSIS
use RDF::Query::Client;
my $query = new RDF::Query::Client ("SELECT * { ?s ?p ?o . }");
while (my $row = $iterator->next) {
print $row->{'s'}->as_string;
}
DESCRIPTION
Constructor
"$query = RDF::Query::Client->new ( $sparql, \%opts )"
Returns a new RDF::Query::Client object for the specified $sparql.
The object's interface is designed to be roughly compatible with
RDF::Query objects, though RDF::Query is not required by this
module.
Options include:
UserAgent - an LWP::UserAgent to handle HTTP requests.
Unlike RDF::Query, where you get a choice of query language, the
query language for RDF::Query::Client is always 'sparql'.
RDF::TrineShortcuts offers a way to perform RDQL queries on remote
SPARQL stores though (by transforming RDQL to SPARQL).
Public Methods
"$query->execute ( $endpoint, \%opts )"
$endpoint is a URI object or string containing the endpoint URI to
be queried.
Options include:
* UserAgent - an LWP::UserAgent to handle HTTP requests.
* QueryMethod - 'GET', 'POST' or undef (automatic).
* QueryParameter - defaults to 'query'.
* AuthUsername - HTTP Basic authorization.
* AuthPassword - HTTP Basic authorization.
* Headers - additional headers to include (hashref).
* Parameters - additional GET/POST fields to include (hashref).
Returns undef on error; an RDF::Trine::Iterator if called in a
scalar context; an array obtained by calling "get_all" on the
iterator if called in list context.
"$query->discover_execute( $resource_uri, \%opts )"
Experimental feature. Discovers a SPARQL endpoint relevent to
$resource_uri and then calls "$query->execute" against that. Uses an
LRDD-like method to discover the endpoint. If you're publishing data
and want people to be able to find your SPARQL endpoint
automatically, the easiest way is to include an Link header in HTTP
responses:
Change the URL in the angled brackets, but not the URL in the rel
string.
This feature requires the HTTP::LRDD package to be installed.
"$query->get ( $endpoint, \%opts )"
Executes the query using the specified endpoint, and returns the
first matching row as a LIST of values. Takes the same arguments as
"execute()".
"$query->as_sparql"
Returns the query as a string in the SPARQL syntax.
"$query->useragent"
Returns the LWP::UserAgent object used for retrieving web content.
"$query->http_response"
Returns the last HTTP Response the client experienced.
"$query->error"
Returns the last error the client experienced.
Security
The "execute" and "get" methods allow AuthUsername and AuthPassword
options to be passed to them for HTTP Basic authentication. For more
complicated authentication (Digest, OAuth, Windows, etc), it is also
possible to pass these methods a customised LWP::UserAgent.
If you have the Crypt::SSLeay package installed, requests to HTTPS
endpoints should work. It's possible to specify a client X.509
certificate (e.g. for FOAF+SSL authentication) by setting particular
environment variables. See Crypt::SSLeay documentation for details.
BUGS
Probably.
SEE ALSO
* RDF::Trine, RDF::Trine::Iterator
* RDF::Query
* RDF::TrineShortcuts
* LWP::UserAgent
AUTHOR
Toby Inkster, <tobyink@cpan.org>
COPYRIGHT AND LICENSE
Copyright (C) 2009-2010 by Toby Inkster
This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself, either Perl version 5.6.0 or, at
your option, any later version of Perl 5 you may have available.