XML Schema: finalDefault, lists and unions

[Jeni Tennison <mail@jenitennison.com>]

Hi,

In XML Schema, the default for the final attributes on xs:element,
xs:complexType and xs:simpleType is given in the finalDefault
attribute on the xs:schema element.

The finalDefault attribute can take the value '#all' or a list of
keywords 'restriction' and 'extension'. The xs:element and
xs:complexType's final attributes take the same values. On the other
hand, the final attribute on xs:simpleType can hold a list of the
keywords 'list', 'union' and 'restriction' rather than 'extension' and
'restriction'.

The fact that finalDefault *can't* take the values 'list' or 'union'
means that it's impossible to by default have simple types take a
final value of 'list' (say), to stop people from deriving lists from
simple types. You can stop derivation by restriction by default, or
all derivation by default, but you can't pinpoint either derivation by
list or union.

Can anyone shed any light on why this is the case?

Just curious,

Jeni
---
Jeni Tennison
http://www.jenitennison.com/