RQTS : tag order

Robert A. (Bob) Morris ram at CS.UMB.EDU
Wed Dec 8 09:16:59 CET 1999

Here's a proposed requirement for data exchange, brought home by one
of Leigh's examples:

<RQT> It should be possible from the data itself, perhaps together
with external resources to which it refers, for software to determine
whether the order matters for any collection of tags in the

One answer is "order always matters". That would be regrettable. For
example, being able to detect that some list is unordered can make it
easier to know whether two data streams represent the same
object. (That's probably a deeper desideratum.)

I am sure this question is addressed in most existing formats; I'm
only arguing it needs to be memorialized as a requirement. I emphasize
"for software to determine". I don't admit the case in which "it's in
the spec" is offered as the answer to this question, unless the spec
is something formal, accessible, and the question can be answered
algorithmically from it. (This is an argument for making specs be in
the same syntax as data, but that's a solution, not a
requirement. It's also an argument why all languages but Lisp are
pointless, but I bet I won't get much sympathy for that position
here... :-) ).

BTW, Leigh, your Subj:
  (XML)shearing files between programs without data loss

I wonder: <rhetorical> an intended pun or just a typo?  </rhetorical>

Bob Morris

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