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4. Protocol Specification
The Information Retrieval application protocol specifies the formats and procedures
governing the transfer of information between a Z39.50 origin/target pair. Sections
4.1 and 4.2 respectively describe
the formats and rules for exchange of Z39.50 application protocol data units
(APDUs). An APDU is a unit of information, transferred between origin and target,
whose format is specified by the Z39.50 protocol, consisting of application-protocol-information
and possibly application-user-data. Sections 4.3 and
4.4 respectively describe rules for extensibility
and conformance requirements.
4.1 Abstract Syntax and ASN.1 Specification
of Z39.50 APDUs
This section describes the abstract syntax of the Z39.50 APDUs, using the ASN.1
notation defined in ISO 8824. The comments included within the ASN.1 specification
are part of the standard.