Re: User-information-field vs. Other-information

From: "Mike Taylor" <mike@indexdata.com>
> Just looking at the standard's specificaton of Init at
> http://lcweb.loc.gov/z3950/agency/markup/04.html
> and I read those familiar paragraphs:
>
> 3.2.1.1.7 User-information-field This parameter may be
> used by the origin or target for additional
> information not specified by this standard.
>
> 3.2.1.1.8 Other-information This parameter may be used
> by the origin or target for additional information not
> specified by the standard. This parameter may be used
> only if version 3 is in force.
>
> (The same things appear in other services' PDUs)
>
> Can anyone remember why we have both of these, and what the
> distinction between them is supposed to be?  From the fact that
> Other-information is only supported in v3, I suppose we can deduce
> that during the gestation period for Z39.50-1995, someone wanted to do
> something that, it was felt, wasn't an appropriate use for
> User-information-field -- but what on earth could that be?

userInformationField was defined simply as EXTERNAL. The ZIG wanted (or
thought it wanted) a more all-purpose, extensible field, and came up with:

   OtherInformation    ::= [201] IMPLICIT SEQUENCE OF
SEQUENCE{
      category               [1]   IMPLICIT InfoCategory OPTIONAL,
      information     CHOICE{
             characterInfo                [2]   IMPLICIT
InternationalString,
             binaryInfo                   [3]   IMPLICIT OCTET STRING,
             externallyDefinedInfo        [4]   IMPLICIT EXTERNAL,
             oid                          [5]   IMPLICIT OBJECT IDENTIFIER}}
--
   InfoCategory ::= SEQUENCE{
         categoryTypeId   [1]   IMPLICIT OBJECT IDENTIFIER OPTIONAL,
         categoryValue    [2]   IMPLICIT INTEGER}

The plan was that alot of "categories" would be defined and some even
registered. But that never really got off the ground. So this was a case of
over-engineering.

Can't use it in version 2 because it wasn't defined until the 1995 version.
However, it has been retrofitted for version 2, see:
http://lcweb.loc.gov/z3950/agency/defns/user-1.html

--Ray

Received on Wednesday, 10 September 2003 11:20:41 UTC