regular expressions - whitespace

[ChristianGruen]

There is some confusion about the rationale for defining the multi-character escape for whitespaces in a recent discussion on Slack:

• \s is limited to [#x20\t\n\r]
• In contrast, \w\ covers [#x0000-#x10FFFF]-[\p{P}\p{Z}\p{C}], i.e., considers the full Unicode range

Do we know the reason?

I assume it’s both too late and out of scope to change that in our specs, but maybe we can improve the XQFO spec and…

• mention why \s does not include \p{Zs} or \p{Z}
• add an example for looking up non-breaking spaces… for example:

matches(
  string-join(('my', 'pleasure'), char(0xA0)),
  '\p{Z}'
)

[ndw]

I think Syd Bauman's proposed rational: that \s matches the S production in XML is almost certainly correct.

It's too late to add such a note to the XML Schemas specification, but we could certainly add one here.

[Arithmeticus]

Equivalent reminders exist within constituent definitions in the serialization spec (1.1, definition), XSLT spec (4 Data Model, para 4, definition), but not the data model spec.

There is a rather opaque reminder in the XPath specs A.3.5.

The XQFO spects have a reminder in the rules and a note of fn:normalize-space, in the 5.6.2 flags documentation for x, a note for fn:tokenize, a note for fn:parse-ietf-date. So, here there, but not everywhere, and not captured as a definition as the other two specs do.

In all, there are already a lot of reminders about what whitespace means scattered throughout the specs. So the failure to communicate is not because no one tried.

One impulse is to keep spreading reminders. Another is to consolidate them and make them more prominent (via hyperlinks). I don't know.

[michaelhkay]

One impulse is to keep spreading reminders

My father taught me a useful principle on this: if you want to bring things to a reader's attention, you need to reduce the amount of text, not to increase it. Very hard to achieve in practice, but certainly, saying things several times in different places can be counter-productive.

[michaelhkay]

It's not easy to add tutorial information for regular expressions given that we specify them by reference to the XML Schema specification, with modifications and additions. There's nowhere obvious to put the requested information without adding a lot of other non-normative material to the spec, and on the whole, I think that would be counter-productive. I'm going to propose closing with no action.

[ChristianGruen]

I'm going to propose closing with no action.

+1. The best place would be the XML Schema spec anyway.

[ndw]

The CG agreed to close this issue without action at meeting 066