Rob,

I think a server may have the following reasons for including
extraResponseData that are independent of what the client requests :

To identify ownership of the data/response.
To show where the response came from.
To provide diagnostic information in the response, not necessarily for the
purposes of the client.
To provide additional data which will help process the response.

The client can ignore data it does not require. Why should it "break" the
processing in the client, unless the client is not conforming to the schema
?.

While the additional parameter is one way of defining the additional data
included in the response (http headers might be an alternative) it requires
the client to know this parameter and that it has a means of setting this
parameter, either automatic or user driven.

Bill


-----Original Message-----
From: Dr Robert Sanderson [mailto:[log in to unmask]]
Sent: 30 December 2004 14:10
To: [log in to unmask]
Subject: Re: British Library Test SRU Service

> I have a problem with the extraResponseData. What is the reasoning behind
> this only being returned if requested ?.

The following reasons:

*  The server cannot know what the client needs without being told, as it
cannot identify a particular type of client.

*  The server may have many different possible extra*Data handlers, and if
it were to return everything, it would bloat the response unnecessarily.

* If the information is not requested, then the client is unlikely to know
how to process it.  At best the client will just ignore it, but at worst
it may break things.

The other option is to include an x- parameter in the URL for SRU.  As the
clients which know about the extension know how to request it, it's a
trivial matter to do so.  Just put &x-tel-info on the end of your SRU URLs
and if it's present, put in your extra informaion.

This was all discussed relatively recently here:
http://listserv.loc.gov/cgi-bin/wa?A2=ind0410&L=zng&T=0&F=&I=-3&S=&P=7614

HTH,

Rob

       ,'/:.          Dr Robert Sanderson ([log in to unmask])
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   ,'--/::(@)::.      Dept. of Computer Science, Room 805
,'---/::::::::::.    University of Liverpool
____/:::::::::::::.  L5R Shop: http://www.cardsnotwords.com/
I L L U M I N A T I


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