XML API specification

Richard Light richard at light.demon.co.uk
Sat Mar 1 09:59:59 GMT 1997

As a postscript to my comments on the API design, I think it is
important that the "event vs. tree" discussion shouldn't muddy the
waters when looking at the API design.  If the XML processor is seen as
a 'server', and the application as a 'client', with the API in between,
it is clear to me that:

- the server's job is to return information about XML documents
requested by the client (and this is its _only_ job!);
- to do this job, the server _must_ parse the document (fully or
partially) in the time-honoured sequential manner;
- the client isn't so constrained, and can ask for as little or as much
as it likes.

For example, in an online browsing application, it is a likely
requirement that the client, in resolving a TEI extended pointer or
HyTime-like XML link, will request a specific element out of an XML
document.  Having retrieved that element, the browser may have no
further use for the XML document from which it came.  So the server
needs to parse through the document until it hits the required element,
then it can stop.  Parsing through the rest of the document would just
be a waste of time.  (Conversely, it makes sense for the server to hold
the results of the parse until it knows the client has no further use
for that document.  It should also be able to pick up the parse where it
left off if necessary.)

I don't think that it should really be the client's job to tell the
server _how_ to do its parsing, except at the formal level (i.e. 'well-
formed' or 'valid').

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Richard Light
SGML and Museum Information Consultancy
richard at light.demon.co.uk
3 Midfields Walk 
Burgess Hill
West Sussex RH15 8JA
tel. (44) 1444 232067

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