XSF Discussion - 2022-12-25

Merry Christmas to all!

Christmas is fraud (:

Ellenor Malik: merry fraud to you then

What does xml:lang affect in practice? Do client even set it to anything other than "en"?

Does xmpp use ns prefixes anywhere aside from that?

yes in stream initiation

otherwise no

> Does xmpp use ns prefixes anywhere aside from that? you mean, does it _not_ use namespaces somewhere? :)

kurisu: yes, anywhere anyone chooses to use prefixes

singpolyma, nobody uses anywhere prefixes

Sorry I meant ns prefixes with attributes

Prefixes vs not are a syntax choice by the producer

everything is qualified by some namespace, and <message xmlns="jabber:client" ...> can be encoded as <jabber:client:message ...>

Oh, specifically namespaced attributes are more rarely useful. Honestly attributes at all are less useful in general

probably

you can theoretically, but practically nobody does it

><jabber:client:message ...> I don't think that's valid xml...

and nobody tried if that would be compatible with clients

or even servers

singpolyma, but does any XEP in practice require namespaced attributes?

not that i know off

I'm just thinking how to parse XMPP correctly and it seems kinda tricky to me b/c of that. Like, if I have expat handle namespaces, I don't know what prefix the producer set, thus I don't see xml:lang="en" but more like http://www.w3.org/XML/1998/namespace:lang="en", and to represent that in DOM internally I still need a prefix... which I don't know... yikes.

Also, will <features xmlns="http://etherx.jabber.org/streams"/> instead of <stream:features/> break stuff?

> ><jabber:client:message ...> > I don't think that's valid xml... yeah, you're probably right, only one colon seems to be allowed by https://www.w3.org/TR/xml-names/#ns-qualnames

`<fwoop:message xmlns:fwoop="jabber:client" ...>` then would be something legal in xml and, afaik, in xmpp

kurisu: when you parse XML the prefixes disappear

^this. they're an artifact of encoding, so to speak

The prefix "xml:" is special because it's build in to XML and not user declared namespace prefix

Turns out you can't inline xmlns in xpath generally. You have to make a local prefix somewhere, maintaining a list of your local made up prefixes... just bruh

there was some relevant discussion on this channel about prefixes on December 03

s/some/extensive/

singpolyma, > when you parse XML the prefixes disappear I thought I read somewhere up the chat xmpp servers and clients are likely to break if non standard prefixes are supplied. In my client I want to build a DOM. I thought the way I'd go would be take an existing xml library and build its dom in parts with expat. But xml libraries it seems won't let you set a namespaced attr without giving it a prefix. And I was just cautious about this because of the above paragraph. But if namespaced attrs aren't used in practice, I suppose I can just set the prefix to auto generated foo1 foo2 I guess haha

> I suppose I can just set the prefix to auto generated foo1 foo2 I guess haha that would change semantics then, no? in absence of prefix, the parent namespace is assumed, iirc

what code language do you use?

and yeah, xpath seems to actually depend on particular prefixes to exist in the document, i.e., it doesn't abstract them away o_O ✏

that would make xpath pretty weird

xpath is terrible in that way, though xpath implementations often allow you to pass a prefix<->uri map into them

ah, that's nicer ✏

mjk: you make up your own prefixes for xpath. It doesn't use ones that may be in document

It just makes the syntax a bit nicer

oh

wikipedia might be wrong there, then: > In the case of an XML document in which the namespace prefix gs has been defined, `//gs:enquiry` will find all the `enquiry` elements in that namespace https://en.wikipedia.org/wiki/Xpath#Node_tests I need to parse the actual spec then

kurisu: you never need to know the prefix in xmpp

kurisu: you need to be able to produce specific prefixes (`stream`) for backward compatibility though

(and as others said, generally avoid generating any prefixes except on the stream header and the stream prefix on nonzas) ✏

so you can safely use expat in a mode which resolves namespaces for you

Is there a mode where Expat doesn't?

Zash: if there is it's called "broken mode please run screaming"

Will <features xmlns="http://etherx.jabber.org/streams"/> instead of <stream:features/> break stuff?

kurisu: only if the implementation is broken ✏

Then you file a bug

Well, in practice are most implementation broken that way or not?

Try it and find out?

Only way to be sure :)

Anything else is a rumour

So does xml:lang factually affect anything in practice in existing implementations

kurisu: Conversations and forks will select an element with a lang matching what language the app is using if one is present

For body at least

Ok so if I plan on resending stanzas should I make sure it's xml:lang="en" not xmlns:fizz="http://www.w3.org/XML/1998/namespace" fizz:lang="en"?

kurisu: that is not legal xml

AFAIK xml: is a special reserved prefix you don't declare it

xml forbids rebinding the xml namespace ✏

see https://www.w3.org/TR/REC-xml-names/#xmlReserved for details

but yes, you do not need to declare it, and if you do, the prefix must be xml