Re: How should a two-digit airport runway number be represented in XML?

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Dimitre Novatchev <[email protected]> writes:
> Why not allow both of these?
>
> In this way, if a human must manually edit the XML document, they will no=
t be committing any mistake writing the number in any of the two possible w=
ays.

When presented with a choice about how to model equivalent structures, ther=
e=E2=80=99s a tendency to say =E2=80=9Cif the representation doesn=E2=80=99=
t matter, accept all of the possible representations and let the user choos=
e the one they like best.=E2=80=9D It makes a lot of sense.

There is an alternative formulation, first introduced to me by Michael Sper=
berg-McQueen in the Schema working group (as I recall). If the order doesn=
=E2=80=99t matter: pick one.

There=E2=80=99s a lot to be said for the simplicity of =E2=80=9Calways two =
digits=E2=80=9D. And it means that a reader used to <runway>09</runway> won=
=E2=80=99t have to pause and consider if <runaway>9</runway> is the same th=
ing. Don=E2=80=99t confuse the human.

The context in the Schema working group was content models where the order =
doesn=E2=80=99t matter. If you=E2=80=99ve got ten elements A, B, C, D, E, =
=E2=80=A6 J and the order doesn=E2=80=99t matter, you can make it an xs:all=
 group, or you can just make it a sequence: A, B, C =E2=80=A6, J.

The xs:all group means that readers and all processing tools have to deal w=
ith 10! possible arrangements. That=E2=80=99s a lot of work for something t=
hat doesn=E2=80=99t matter!

(In point of fact, I think that there are lots of cases where we say that o=
rder doesn=E2=80=99t matter but leave unsaid that what that really means is=
 that we don=E2=80=99t have consensus on the right order. I want to put A b=
efore B when I=E2=80=99m writing but Josephine wants to put C before A. But=
 I still like the simplicity of =E2=80=9Cpick one.=E2=80=9D And if you do, =
you=E2=80=99ll quickly find out from your users if the order *does* matter =
in some way!)

                                        Be seeing you,
                                          norm

=2D-
Norm Tovey-Walsh <[email protected]>
https://norm.tovey-walsh.com/

> Substitute "damn" every time you=E2=80=99re inclined to write "very"; your
> editor will delete it and the writing will be just as it should
> be.--Mark Twain

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