ABSTRACT
Information retrieval (IR) protocols support effective and interoperable intersystem search and retrieval. Although intersystem search methods have been envisioned and under development since the 1970s, it was the Z39.50 IR protocol, first released in 1988, that demonstrated real-world possibilities for such search and retrieval. As the networked information environment changed with the emergence of the World Wide Web, the need for standard IR protocols did not disappear, and one can argue the need is even more compelling given both the visible and invisible Web. A new protocol, based on the experience from Z39.50 but simpler and more comprehensible than Z39.50, is now being used for Web search and retrieval. Search and retrieve via URL (SRU) uses Web technologies and standards resulting in a Web friendly protocol that provides standard search access to existing Z39.50 resources and a wide-range of new non-catalog digital resources. This entry provides both an overview of the two protocols and technical details to understand both. A brief discussion of IR and communications protocols provides background to the specifics of these two IR protocols. Although communication protocols are by their nature technical specifications, this entry focuses on an overview of the functions and capabilities of the protocols. It uses technical concepts and terminology from the protocols to help explain how the protocols work but limits discussion of technical details.
