Wednesday, February 18, 2004

Catalog Searching

The SRW Maintenance Agency at the Library of Congress, in conjunction with the SRW Development Group, announces the release of version 1.1 of SRW, the Search/Retrieve Web Service; SRU, Search and Retrieve by URL; and CQL, the Common Query Language.

SRW is an XML-based protocol designed to be a low-barrier-to-entry solution for searching and other information retrieval operations across the internet. It uses existing, well tested, and easily available technologies, such as URI, XML, SOAP, HTTP, and XPath. The design reflects the many years of experience gained developing and using Z39.50; SRW is both robust and easy to understand while retaining many of the important aspects of Z39.50. Web technologies reduce the barriers to new information providers allowing them to make their resources available via a standard search and retrieve service. Building on Z39.50 semantics enables the creation of gateways to existing Z39.50 systems. The protocol may be carried via SOAP or as parameters in a URL. When carried via SOAP, it is referred to as SRW; via URL, as SRU.

CQL is a formal language for representing queries to information retrieval systems, including web indexes, bibliographic catalogues, and museum-collections information. Traditionally, query languages are either (on one hand) powerful and expressive but complex and unfriendly -- SQL, Xquery -- or (on the other hand) simple and intuitive but neither powerful nor expressive, for example, Google. CQL's goal is to combine the simplicity and friendliness of Google searching with the expressive power of Z39.50, supporting queries ranging from very simple to arbitrarily complex expressions.

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