December 1999

Originator: ZIG

Date: 12/99

Amendment Concerning: New Query Type(s)

Reference in Document: 3.2.2.1.1, and ASN.1 for APDUs: Z39-50-APDU-1995, definition of Query

Reference in Maintenance Agency page: None.

Z39.50 defines a number of query types, and does not provide any mechanism to define or register addtional query types, short of amending the standard. The purpose of this amendment is to relax this restriction so that new query types may be defined and/or registered without amending the standard. Two approaches are considered:

1. A new query type, type 104, would be defined (by this amendment). It would be defined as EXTERNAL. New queries would be registered with object identifiers, would utilize the type 104, and would be distinguished by their object identifier (carried along implicitly in the EXTERNAL structure).

2. This amendment would simply state that new query types may be registered (by integer) outside of the standard. Thus the maintenance agency would assign new query types -- for example: 105, 106, etc. -- in a manner similar to that by which it assigns object identifiers, except that integers and not object identifiers would be assigned for query types.

Thus adoption of this amendment will require that one of these two approaches be selected (and this amendment re-written). Selection of approach 2 would not preclude a type-104 query being defined, as EXTERNAL, as described in approach 1.

Ed. Note: Two variation of this amendment are supplied. Adoption of this amendment requires that one of the variations be selected, and this amendment re-written.

• Variation 1
  A new query type, type 104, is defined.
  

  Query (within the Z39.50 ASN.1 APDU definition) is currently defined as:

  	Query  ::=	CHOICE{
  	type-0		[0]	ANY,  
   	type-1		[1]	IMPLICIT RPNQuery,
   	type-2    	[2]	OCTET STRING,
   	type-100	[100]	OCTET STRING,
   	type-101	[101]	IMPLICIT RPNQuery,
  	type-102	[102]	OCTET STRING}
  

  It is re-defined by this amendment as:

  Query  ::=	CHOICE{
  	type-0		[0]	ANY,  
  		......	
   	type-102	[102]	OCTET STRING,
  	type-104	[104]	IMPLICIT EXTERNAL}

• Variation 2
  The Z39.50 standard implicitly requires that all Z39.50 query types be defined integrally within the protocol, either within the published standard or by amendment. By this amendment, new query types may be defined and assigned an integer type, without requiring amendment to the Z39.50 standard. The Z39.50 Maintenance Agency will establish procedures for assigning new query types.

  Query is re-defined by this amendment as:

  Query  ::=	CHOICE{
  	type-0		[0]	ANY,  
  		......	
   	type-102	[102]	OCTET STRING
  -- [103] and above are reserved for definition and registration of new query types.
  	}

For consideration by the ZIG at the January 2000 meeting.