Client-server implications of the remote database search in the library catalogues using the Z39.50 standard
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Search in Internet databases is based on the Z39.50 protocol, which specifies the client/server interaction. Since it was originally proposed in 1984, the standard has undergone several revisions. The official source is the Library of Congress Z39.50 Maintenance Agency (USA). Basically the Z39.50 protocol stack exists between the TCP/IP protocol stack and the client front end interface. Z39.50 consists of basic structural blocks (Initialization, Search, Retrieval, Sort, etc.) for communication between the origin and the target (client/server). A wide spectrum of programming approaches in the development of threes systems can be detected. For example, ZACK, a system for simultaneous searching in several library databases was developed in the Technical University of Berlin (free download from http://www.biblio.tubs.de/zack/). Commercial software is often based on more complicated approaches allowing efficient interaction (e. g. OCLC SiteSearch Suite, EndNote, Elektra and others). The importance of the development of co-operative bibliographic retrieval networks is paramount for the computer and Internet implementation in scientific libraries. Search engines provide access to information that can be indexed on the Internet, basically web pages and FTP archives. While pure search engines employ robots, Web catalogues give access to systematized information under certain categories. It is the trend, that most search engines develop to portals. Existing virtual libraries are the WWW Virtual Library Veterinary Medicine, NetVet and Vetgate. Our own virtual library ViFaVet at: http://elib.tiho-hannover.de/virtlib/ and http://elib.tiho-hannover.de/virtlib/index-e.html went online September 2001. It offers: -Subject Guide, - Databases, - Online Contents Veterinary Medicine, - Full Text Documents, - OPAC, - Project Information, - What's New? It can be browsed and searched through a Z39.50 interface. An ordering form is given and an input-form for suggesting additional resources are provided. For the future a meta-catalogue of European veterinary library holdings and a subject specific Internet search-engine are planned. These will also employ the Z39.50 interface to make them accessible.