[lxml-dev] [objectify] schema type registry: QNames for xsi:type?

[jholg at gmx.de]

Hi Stefan,

> > Is it easily possible to use QNames in the xsi-type lookup system?
>
> I believe this would be the right thing to do, as lxml should be
> consistent.
> If XMLSchema handles it one way, objectify should handle it the same way.
>
> However, it is actually harder than you might think. In ET, namespaces use
> the
> Clark notation, but the standard requires prefixes here. Assuming that
> people
> always use "xsd" as prefix is error prone, so we'd have to look up the
> right
> prefix for each element when we store it and make sure the namespace is
> declared. We should definitely use the xsd prefix if we declare it
> internally,
> to make it less likely that users deploy the same prefix for a different
> namespace.
>
> More importantly, when we look up the type, we'd have to check for the
> namespace referenced by the prefix to make sure it's an XMLSchema type.
>
> Alternatively, we could switch to writing out the prefixed version
> internally
> and just ignore the prefix when figuring out the type. That would prevent
> people from using data types from other namespaces, but that's an unlikely
> use
> case anyway. If you want to do that, you can stick to registering a Python
> type.

I could certainly live with that for my application :-).

> I wouldn't mind changing it to the prefixed version - as usual: better now
> than later. Changing this means that the typed XML that newer versions of
> objectify write out will not be read as expected by version 1.2. Sounds
> acceptable to me.

Again, this would work for me.
I guess the objectified.Element() factory should then have the schema namespace added to its _DEFAULT_NSMAP, right?

> I would like to hear other opinions on this before the release of 1.3,
> which
> will define the way this will be handled in the future.

When parsing a document that declares the schema namespace, will the prefixed write-out be able to pick up this prefix, or will it always use "xsd"?

Holger

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