Some Key

Some Key Z39.50 

The basic function of Z39.50 is to negotiate a connection between the client and server on two systems, execute a search, and return the formatted results to the user’s screen. In a Z39.50 session, the Z39.50 client software that initiates a request for the user is known as the Origin. The Z39.50 server software system that responds to the Origin’s request is called the Target


Z39.50 groups together certain protocol devices that support certain tasks (e.g., negotiating a session, communicating a search, and requesting retrieval records) into Facilities

  1. Initialization Facility   allows the Origin (client) and Target (server) to negotiate and establish a Z39.50 search session, known as a Z-Association
  2. Search Facility  allows the user to formulate a search query using an interface format familiar to the user
  3. Present Facility  allows the user to request that some or all of the records identified as meeting the search criteria be transmitted from the server to the client.
Other Z39.50 Facility protocols exist to support such features as:
  • Sort the results as specified by the user.
  • Delete search results, either entirely or for specified records.
  • Scan (browse) through index lists of items such as subject terms, titles, author names, and other database fields.
  • Access Control through authentication and passwords.
  • Resource Control and termination of Z39.50 search sessions by the client or server

Attributes and attributesets
When executing a Z39.50 search, the user specifies search terms that will be used to match against access points in the database. The user’s query identifies information, or attributes, about those search terms that specify how that term is to be treated when used in the search.

There are several different types of attributes:
  • Use attributes indicate database access points— searchable fields or indexes that can be specified in the search. 
  • Relation attributes are descriptors that specify characteristics such as less than, greater than, or equal to. A search for books published during or later than 1996 would use relation attributes in the query.


A profile is a detailed specification of Z39.50 features and functions
that an implementation will support, improving interoperability by:
  • assisting customers 
  • defining a core set
  • increasing the market
  • improving users’ success in information retrieval
  • leveraging local investment

Niso Press (2002). Z39.50 a primer and the protocol. Date of retrieve 1/8/2011.
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