Biblio Tech
Information Technology for Libraries

Z39.50 part 2

Updated: 12 April, 2001


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Z39.50: Part 2 - Technical Details       by Peter Evans


Part 1 of this article covered the basic working and implications of the Z39.50 standard for librarians and library systems and products. Part 2 covers the detail - it describes the different facilities of Z39.50 but concentrating on the implications of the standard for librarians.  It aims to equip the librarian with enough knowledge to understand what is possible so that he/she can manage the set-up of Z39.50 servers or talk to vendors about their product’s capabilities.  It is presented in sections to for ease and speed of retrieval and reading.

I have not tried to make clear which version of Z39.50 supports what function. Good products should be supporting most of the features described here and be looking forward to version 4.  Note also that not every detailed parameter is described - the aim is to bring out the functionality of the standard for the librarian - not to provide a reference for the programmer.


Current Page

Z39.50 Core Rectangle Rectangle Rectangle Rectangle Rectangle

1: Core facilities; Initialisation, Search, Query, Response, Retrieval: Present, Segment, Result-set-delete
Access Control, Account control, Sort, Browse
Extended services, Explain, Termination, Future, Implications .
Z39.50 Diagram: a graphical representation of Z39.50
Attributes for Bib-1; Fields, operators etc.
Record Syntaxes; MARC formats, SUTRS. GRS-1

Summary of a Z39.50 session

During the Z-Association, the Z-client (origin) and Z-server (target) exchange a series of messages.  Each message is identified as a technical “service”. The services are grouped into what the standard calls “facilities”. There are eleven facilities:



1.   Initialisation

setting up the Z-Association, negotiating levels of service

2.   Search

sending a search string at a database and getting back a result set and the first few records.

3.   Retrieval

Retrieval of records from the result set as specified by the Z-client.

4.   Result-set-delete

deleting a set of search results held on the Z-server

5.   Access Control

allowing the Z-server to ask for passwords etc.

6.   Accounting / Resource   Control

allowing accounting, credit control etc.

7.   Sort

sorting a result set in a defined order on the Z-server

8.   Browse

scanning an index on the Z-server

9.   Extended services

allowing Z-client to start a “task packages” e.g. ILL on Z-server

10. Explain

allowing the Z-client to query a database of implementation details on the Z-server

11. Termination

Closes down a Z-Association.

A typical Z-39.50 session goes through facilities 1-3 and then terminates when the client has the records it wants.  The other facilities add account control and enhanced features like Sort, Browse, ILL etc.

Next section: Core services

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