> > 1) that when a client ask for this new feature a server that did not
> > implement this feature should be able to give a "reasonable"
> > response - not being an error message.
> > 2) that when a server provides a new feature the client should be
> > able to neglect this when he is "not aware" of this technology.
> Hi, Theo. I agree with your second criterion, but certainly not the
> first. If we are to enable SRW to provide solid, reliable services,
> then the one thing they mustn't be allowed to do is fudge the issues.
> If I ask a server to so something a certain way, it must not be at
> liberty to ignore that and do it a different way. It is only polite
> for a server that can't honour my request to come right out and say
Diagnostics are easier to implement than fudged results anyway! If you're
not going to implement the feature at all, then you might as well take the
easiest route out ... a diagnostic.
> still not really great. What it means is that XPath-aware clients
> would need, every time they submit an XPath'd search, to explicitly
> check whether the XPath was honoured (silence) or ignored (included as
> an unknownParameter in the response).
I agree with Mike (and Matthew's original post) completely.
Some other reasons: echoedRequest/unknownParameter is only available in
SRU. Meaning that SRW and SRU would have different semantics about how to
deal with unimplemented features.
Some features won't be checkable by the client via inspection. For
example various types of sort. So the client would never know if it was
performed or not.
Sometimes the client will be making the good faith assumption that the
server will either give a diagnostic or perform the request as asked. For
example I might search a database full of megabyte+ records and ask for
/record/title | /record/creator in the XPath with a maximumRecords of 25.
If the server just returns the full 25 megabytes+ of records, then chances
are likely that the client will choke (quite apart from being a total
waste of time and resources).
For small records, you might as well retrieve the whole thing. XPath is
useful for extracting sections of large records, or for paging through a
single record that's too long to conveniently display at once.
,'/:. Dr Robert Sanderson ([log in to unmask])
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