Z39.50-1995 Amendment 5:
String Identifiers for Schemas

November 2001
Amendment Number: Z39.50-1995 Amendment 5
Formerly Z39.50MA-AM0007

Originator: Maintenance Agency

Date: 9/01

Amendment Concerning: CompSpec; how to indicated desired schema

Reference in Document: Definition of Specification within ASN.1 for APDUs

Reference in Maintenance Agency page: http://www.loc.gov/z3950/agency/asn1.html

Background:

The Z39.50 Present request may include a schema identifier; thus it allows the client to request that records be supplied according to a specific schema. However in Z39.50-1995 the identifier must be an ISO object identifer (OID), and it is assumed that the schema is a GRS-1 compatible schema (i.e. that the record syntax will be GRS-1). There is now growing interest in sending XML records, i.e. where the record syntax is XML rather than GRS-1. XML as a record syntax, coupled with an XML schema, is analogous to GRS-1 as a record syntax coupled with a GRS-1style schema. However, XML schemas are generally not identified by OIDs, but rather by URIs. Thus it is proposed that the restriction wherby a schema is identified by an OID be relaxed so that it may alternatively be indentified by a string.

Amendment:

  1. Amend the definition of Specification.
    It is defined as follows:

    Specification ::=
    SEQUENCE{
    schema [1] IMPLICIT OBJECT IDENTIFIER OPTIONAL,
    elementSpec [2].......

    2. Change it to:

    Specification ::=
    SEQUENCE{
    schema CHOICE{
    oid [1] IMPLICIT OBJECT IDENTIFIER,
    uri [300] IMPLICIT InternationalString }     OPTIONAL,
    elementSpec [2].......

     

  2. Define an option bit for this feature. When negotiated, the server will recognize 'stringSchema' if supplied in specification; if it is not negotiated, the server will not.
Status:
Approved by ZIG at the October 2001 meeting. Approved by Maintenance Agency November 2001.

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