Search (6 results, page 1 of 1)

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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.

Source

Encyclopedia of library and information sciences. 3rd ed. Ed.: M.J. Bates

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Content

"Seit zwei Jahrzehnten nutzen vor allem Bibliotheksverbünde das Protokoll Z39.50, um ihren Benutzern im Internet die simultane Abfrage mehrerer Datenbanken zu ermöglichen. Jetzt gibt es einen Nachfolger dieses Protokolls, der eine einfachere Implementierung verspricht. Damit ist auch eine größere Verbreitung für die Suche in verteilten Datenbeständen anderer Institutionen, wie z.B. Archiven und Museen, wahrscheinlich. SRW/U (Search and Retrieve Web Service bzw. Search and Retrieve URL Service, www.loc.90v/z3950/agency/zing/srw) wurde von einer an der Library of Congress angesiedelten Initiative entwickelt und beruht auf etablierten Standards wie URI und XML. Die mit SRW und SRU möglichen Abfragen und Ergebnisse unterscheiden sich nur in der Art der Übertragung, verwenden aber beide dieselben Prozeduren. Davon gibt es nur drei: explain, scan und searchRetrieve. Die beiden Erstgenannten dienen dazu, allgemeine Informationen über den Datenanbieter bzw. die verfügbaren Indexe zubekommen. Das Herzstück ist die search-Retrieve-Anweisung. Damit werden Anfragen direkt an die Datenbank gesendet und die Parameter des Suchergebnisses definiert. Verwendet wird dafür die Retrievalsprache CQL (Common Query Language), die simple Freitextsuchen, aber auch mit Boolschen Operatoren verknüpfte Recherchen ermöglicht. Bei SRU werden die Suchbefehle mittels einfacher HTTP GET -Anfragen übermittelt, die Ergebnisse in XML zurückgeliefert. Zur Strukturierung der Daten dienen z.B. Dublin Core, MARC oder EAD. Welches Format von der jeweiligen Datenbank bereitgestellt wird, kann durch die explain-Anweisung ermittelt gebracht werden."

Source

Information - Wissenschaft und Praxis. 56(2005) H.5/6, S.274

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Source

Grundlagen der praktischen Information und Dokumentation. 5., völlig neu gefaßte Ausgabe. 2 Bde. Hrsg. von R. Kuhlen, Th. Seeger u. D. Strauch. Begründet von Klaus Laisiepen, Ernst Lutterbeck, Karl-Heinrich Meyer-Uhlenried. Bd.1: Handbuch zur Einführung in die Informationswissenschaft und -praxis

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Source

Journal of the American Society for Information Science and technology. 54(2003) no.2, S.161-168

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Abstract

This article will examine the Z39.50 Information Retrieval protocol. It will look at some of the history of the protocol, its operation, and some of the major projects that have made use of it. There has been enough written (perhaps too much) about Z39.50 in the last several years so it is not intended to be a tutorial or detailed description of the protocol. The material that will be presented will try and put some context around the discussion. For those readers who are interested in delving into Z39.50 in a more technical manner, references to much of the material that has been written about it over the years will be provided at the end. Finally, the article will conclude with some thoughts on how technology and technological infrastructure have changed in the years since Z39.50 was initially developed and deployed, and where the protocol has so far lived up to its goals, and where it has perhaps failed to meet some of the high expectations that at least some people involved in the Z39.50 community held for it. The article will conclude with some of the author's speculations (and they are really no more than that) of what the future role of Z39.50 is likely to be.