XSD datatypes

[Jason S]

I'm using RELAX NG but my question is about XSD datatypes. Is there
any way to combine patterns? Right now I have this: (a chain of
identifiers, the first being strict e.g. starting w/ letter or
understore, the rest can be letters, numbers or underscore, the
separator being a '.')

<define name='identifie r-chain'>
<data type="token">
<param name="pattern"> ([A-Za-z_][A-Za-z_0-9]*)(\.[A-Za-
z_0-9]+)*</param>
</data>
</define>

is there any way to break this up into sub-patterns?
e.g.

<define name='identifie r'>
<data type="token">
<param name="pattern">[A-Za-z_][A-Za-z_0-9]*</param>
</data>
</define>
<define name='secondary-identifier'>
<data type="token">
<param name="pattern">[A-Za-z_0-9]+</param>
</data>
</define>
<define name='identifie r-chain'>
<ref name='identifie r' />
<zeroOrMore>
<data type="token">
<value>.</value>
<ref name='secondary-identifier' />
</data>
</zeroOrMore>
</define>