Fragment Syntax

For level 2 segmentation when a record is segmented into fragments, each fragment may take the form OCTET STRING or EXTERNAL. The definition below is provided for the case where the target chooses to send fragments as EXTERNAL. Its purpose is to allow the target to reflect the real syntax (i.e. the OBJECT IDENTIFIER which would have otherwise been used within the EXTERNAL if the record were not segmented) in a way that does not violate ASN.1 encoding rules.

FragmentSyntax
{Z39-50-recordSyntax fragment (107)} DEFINITIONS ::=
BEGIN
--
-- For level 2 segmentation when a record is segmented into fragments, each
-- fragment may take the form OCTET STRING or EXTERNAL. When the target
-- chooses to send fragments as EXTERNAL, it may use the format below. This
-- format is provided to allow the target to reflect the real syntax (i.e. the
-- OBJECT IDENTIFIER which would have otherwise been used within the
-- EXTERNAL if the record were not segmented) in a way that does not violate
-- ASN.1 encoding rules.
--
-- This fragment syntax should be used with the following two provisions:
--  (1) If the target uses this format for the starting fragment of a record,
--       then it should use this format for all subsequent fragments
--       (intermediate fragments and final fragment) of that record.
--  (2) 'syntax' (the OBJECT IDENTIFIER that identifies the real syntax of the
--       record) must occur in the starting fragment and only in the starting
--       fragment (must be omitted in intermediate fragments and final
--       fragment).

Fragment ::= SEQUENCE {
  realSyntax      [1] IMPLICIT OBJECT IDENTIFIER OPTIONAL,
                       -- Required in starting fragment. 
                       -- Must be omitted in subsequent fragments.
  remainingOctets [2] IMPLICIT INTEGER OPTIONAL,
                       -- Target estimate of how many octets 
                       -- left after this fragment.
  fragment        [3] IMPLICIT OCTET STRING}
END