ANSI Z39.50

Z39.50 is an American National Standard for information retrieval. It began as a simple information retrieval standard for bibliographic data (WAIS), but has now evolved into a rich set of interoperable services for client-server based search and retrieval, for any information discipline. The Z39.50 network protocol standard was developed to overcome the problems associated with multiple database searching, such as having to know the unique search procedures of each system. The protocol is session-oriented and stateful (in contrast to other Internet protocols such as HTTP). The Z39.50 is recognized world-wide and has was approved by the International Organization for Standardization (ISO) as an ISO Standard - ISO 23950: 1998.

Z39.50-1995 contains versions 2 and 3 of the standard. Version 2 was published in 1992 as ANSI/NISO Z39.50-1992. Version 3, incorporates many more features than Version 2, to support both bibliographic and non-bibliographic searching. The latest version, Z39.50-2003 also specifies Versions 2 and 3, and additionally, incorporates many clarifications, amendments, defect corrections and implementer agreements.

Many public profiles to the Z39.50 standard exist. A profile specifies the use of a particular standard, to support a particular application domain, community of environment. The base profile of Z39.50 is called bib-1 and is the main set appropriate to the bibliography world. GILS is developed on the basis of Z30.50 bib1 attributes, but in addition, contains extra attributes and references. GEO profile builds on bib-1 and GILS by extending the metadata model to include data elements from the Content Standard for Digital Geospatial Metadata maintained by the FGDC. CIP is both a profile and an extension of Z39.50. CIP is a profile of Z39.50 using messages, attributes, and elements in the standards as well as defining CIP-specific attributes and elements. CIP is an extension of Z39.50 through the addition of collections as a data structure and the addition of an ordering facility. Searches can be targeted at Collections, Product or Guide inventories. Retrieval of Browse products is supported. The OGC Catalog Interface standard has a general model and several profiles, e.g., CORBA profile, Web Profile. The OGC catalog interface Web profile is compliant to Z39.50. It contains constructs for the mandatory functions of search and retrieval, and for the optional functions of data access (order) using CIP order mechanism. The Z39.50 messages have been transformed into XML based messages for easier implementation. OGC catalog interface standard is data model independent. CIP is aligned with GEO and GILS profiles.

The Standard is currently maintained by the Library of Congress .