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Re: APIs, messaging

On 22/05/2001 18:29:37 Simon St.Laurent wrote:

>It seems like we have people who want to use XML the same way they've
>used data structures in programs, building tightly-defined APIs to close
>tolerances the same way they've built programs for the last few decades.
>APIs are built and documented and developers have to conform to the
>rules of the API to use them.
>There's another group of people who want to use XML to get out of that
>world of close tolerances and into a much less precise approach where
>messages are exchanged and things may or may not happen depending on the
>understandings of the sender and the receiver.  Message formats may or
>may not be documented and developers can use information for processes
>quite different from the original design.
>Does that seem like a reasonable breakdown of the situation?

Sure, but even within this there are distinctions. Let's call it validating
(first group) vs. well-formed (second group).  Within the validating group, the
driver for demanding tight definitions can be that close enough is simply not
good enough, e.g. for XML messages representing financial transactions.  In
areas like this, your users may not want you to be robust and tolerant of
differences from what is expected, they may just want you to reject it.  Schemas
are only part of the game here, but an important part.

However, also within the validating group will be people who want to move as
much as possible of the validation code out of the main application that
processes it.  To robustly parse well-formed XML means doing all necessary
validation yourself, and that tends to complicate your application architecture
(the lack of standard "validation" API for XML is the real problem here, but
that is another thread ...).  So, the "well-formed" group are those whose users
demand that applications carry on as robustly as possible regardless of the
content of the messages they receive, and who in addition can afford to
implement all the validation that they require in their own "ad hoc" manner.

Anthony B. Coates
Leader of XML Architecture & Design
Chief Technology Office
Reuters Plc, London.

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