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Scan Questions

From: Mike Taylor <mike@indexdata.com>
Date: Wed, 28 Apr 2004 11:21:40 +0100
Message-Id: <200404281021.i3SALeUT004580@localhost.localdomain>
To: www-zig@w3.org

Sorry to arrive at this discussion about nine years late, but as I
come to integrate contributed Scan code into the Net::Z3950 Perl
module, I've been carefully reading what the on-line Z39.50 standard
says about Scan, and there seem to be a couple of mistakes or
ambiguities.  I have no idea whether these issues are reflected in
Z39.50-2003, as the HTML on the site is still from the 1995 version.


In section 3.2.91 (Scan Service), towards the bottom of the page
	http://lcweb.loc.gov/z3950/agency/markup/05.html
Table 12 shows the parameters of the Scan request and response.  The
"Number-of-entries" parameter is listed as being in the response, but
not the request; but the below indicates that it is in both:

	3.2.8.1.4 Number-of-entries. The origin indicates the proposed
	number of entries to be returned. The target indicates the
	actual number of entries returned. If the actual number is
	less than the proposed number, the reason is indicated in
	Scan-status.

And the ASD.1 at
	http://lcweb.loc.gov/z3950/agency/asn1.html#ScanRequest
confirms this.


The ScanResponse ASN.1 at
	http://lcweb.loc.gov/z3950/agency/asn1.html#ScanResponse
includes a parameter

	attributeSet                 [8]    IMPLICIT AttributeSetId

which does not seem to be documented in the prose.  What is this?


What the heck is suggestedAttributes all about?  The prose says:

	A list of suggested attributes for use in subsequent Scan
	requests (useful for scanning multiple indices, e.g. author
	and title, at the same time).

but that doesn't clarify things much for me.


Why is alternativeTerm a SEQUENCE OF AttributesPlusTerm rather than
just a single AttributesPlusTerm?  Both the name of the ASN.1 element
and the prose ("A suggested alternative term.") are clear that a
single term is expected here.


Has anyone, ever, in the history of the universe, implemented
OccurrenceByAttributes?  :-)

 _/|_	 _______________________________________________________________
/o ) \/  Mike Taylor  <mike@indexdata.com>  http://www.miketaylor.org.uk
)_v__/\  How hard can _that_ be?

--
Listen to my wife's new CD of kids' music, _Child's Play_, at
	http://www.pipedreaming.org.uk/childsplay/
Received on Wednesday, 28 April 2004 06:22:04 GMT

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