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fwd: alwaysMatches in BIB-1 and the Utility Set

From: Ray Denenberg <rden@loc.gov>
Date: Thu, 12 Sep 2002 10:56:13 -0400
Message-ID: <3D80AB0D.8DF33CE2@loc.gov>
To: zig <www-zig@w3.org>

Forwarding at the request of Mike Taylor.

From: mike@miketaylor.org.uk

> To: (ZIG list)
> Subject: alwaysMatches in BIB-1 and the Utility Set
> Reply-to: mike@miketaylor.org.uk
> Dear ZIGgers,
> As the specifications for ZeeRex (explain.z3950.org) approach a point
> where we can pronounce them stable, we've found a need for the ability
> to search for all the records in a ZeeRex database.  The current
> ZeeRex searching specification at
>         http://explain.z3950.org/search/index.html
> has this to say:
>         To search for all the records in a ZeeRex database, use the
>         Utilty attribute set's alwaysMatches comparison attribute
>         (type 8, value 1) with any search-term (the term itself is
>         ignored).  In Index Data's prefix-query notation, this is
>         @attr util 8=1 x.
> But re-reading the description of the Utility Set's alwaysMatches
> relation in
>         http://lcweb.loc.gov/z3950/agency/attrarch/util.html
> we found that the prose does not necessarily say what we thought it
> said, and wanted it to say:
>         8. Comparison
>         The following two values are used to test for the existence of
>         an access point, not its value.  When the comparison is Always
>         Matches, it succeeds if and only if the access point exists
>         (regardless of whether there is a value for the access When
>         point).  the comparison is Never Matches, it succeeds if
>         and only if the access point does not exist.  These two values
>         are used with null term:
>           o Always Matches (Value =1)
>           o Never Matches (Value =2)
> Whereas the description of the corresponding relation attribute in the
> good ol' BIB-1 attribute set's semantics document is much more
> helpful.  In
>         ftp://ftp.loc.gov/pub/z3950/defs/bib1.txt
> we read:
>         Relation attribute AlwaysMatches -- when the Relation
>         attribute AlwaysMatches occurs:
>         - The target ignores the supplied term.
>         - If the Use attribute is Any or Anywhere, then all records
>           are to be selected.
>         - If a Use attribute other than Any or Anywhere is supplied,
>           all records are selected for which the access point
>           corresponding to the supplied Use attribute is
>           meaningful.  For example: if the Use attribute is Title,
>           all records that have a title field are selected.
> So our questions are: was the Utility Set's definition of
> alwaysMatches deliberately changed from that in BIB-1?  By whom?  Why?
> Can we use the Utility Set's alwaysMatches relation to find all
> records?  If so, should we use some specific access point in
> conjunction with it?  Which one?  And can the Utility Set's prose be
> changed to spell this out?
> Thanks.  That's all -- just the seven questions :-)
>  _/|_    _______________________________________________________________
> /o ) \/  Mike Taylor   <mike@miketaylor.org.uk>   www.miketaylor.org.uk
> )_v__/\  "This redistribution of wealth's not as simple as I thought"
>          -- Monty Python.
Received on Thursday, 12 September 2002 10:53:23 UTC

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