SRU(3) Search and Retrieval by URL


## a simple CGI example
use SRU::Request;
use SRU::Response;
## create CGI object
my $cgi = CGI->new();
## create a SRU request object from the CGI object
my $request = SRU::Request->newFromCGI( $cgi );
## create a SRU response based from the request
my $response = SRU::Response->newFromRequest( $request );
if ( $response->type() eq 'explain' ) {
} elsif ( $response->type() eq 'scan' ) {
} elsif ( $response->type() eq 'searchRetrieve' ) {
## print out the response
print $cgi->header( -type => 'text/xml' );
print $response->asXML();


The SRU package provides a framework for working with the Search and Retrieval by URL (SRU) protocol developed by the Library of Congress. SRU defines a web service for searching databases containing metadata and objects. SRU often goes under the name SRW which is a SOAP version of the protocol. You can think of SRU as a RESTful version of SRW, since all the requests are simple URLs instead of XML documents being sent via some sort of transport layer.

You might be interested in SRU if you want to provide a generic API for searching a data repository and a mechanism for returning metadata records. SRU defines three verbs: explain, scan and searchRetrieve which define the requests and responses in a SRU interaction.

This set of modules attempts to provide a framework for building an SRU service. The distribution is made up of two sets of Perl modules: modules in the SRU::Request::* namespace which represent the three types of requests; and modules in the SRU::Response::* namespace which represent the various responses.

Typical usage is that a request object is created using a factory method in the SRU::Request module. The factory is given either a URI or a CGI object for the HTTP request. SRU::Request will look at the URI and build the appropriate request object: SRU::Request::Explain, SRU::Request::Scan or SRU::Request::SearchRetrieve.

Once you've got a request object you can build a response object by using the factory method newFromRequest() in SRU::Request. This method will examine the request and build the corresponding result object which you can then populate with result data appropriately. When you are finished populating the response object with results you can call asXML() on it to get the full XML for your response.

To understand the meaning of the various requests and their responses you'll want to read the docs at the Library of Congress. A good place to start is this simple introductory page: For more information about working with the various request and response objects in this distribution see the POD in the individual packages:

  • SRU::Request
  • SRU::Request::Explain
  • SRU::Request::Scan
  • SRU::Request::SearchRetrieve
  • SRU::Response
  • SRU::Response::Explain
  • SRU::Response::Scan
  • SRU::Response::SearchRetrieve
  • SRU::Server

Questions and comments are more than welcome. This software was developed as part of a National Science Foundation grant for building distributed library systems in the Ockham Project. More about Ockham can be found at


To use SRU::Server and Catalyst::Controller::SRU, one must install CGI::Application and Catalyst, respectively. In a future release Catalyst::Controller::SRU might be moved to an independent module.


  • create a client (SRU::Client)
  • allow searchRetrieve responses to be retrieved as RSS
  • make sure SRU::Server can function like real-world SRU interfaces
  • handle CQL parsing errors
  • better argument checking in response constructors


Ed Summers <[email protected]>


This software is copyright (c) 2013 by Ed Summers.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.