Relative URI's in xml:base

There are no discussions or examples in the XML Base document on the use of
relative URI's as values for XML Base.  For example, would something like
this be legal:

<TESTSUITE>
<TESTCASES xml:base="xmlconf/">
    ...   test cases where URI's are relative to document's base URI +
xmlconf/
</TESTCASES>
</TESTSUITE>


In regards to the problem with entity boundaries, you could ensure that you
get the same behavior regardless of whether the DOM strips EntityReference's
by explictly specifying the base URI of the entity in the containing
element.  If the processor maintains the EntityReference reference, then the
xml:base is out of scope and ignored.  If the DOM processor drops the entity
reference, then xml:base is incorrectly applied but it has the same result.

<!DOCTYPE ...[
<!ENTITY xmlconf SYSTEM 'xmlconf/xmlconf.xml'>
]>
<TESTSUITE>
<TESTCASES xml:base="xmlconf/">
    &xmlconf;
</TESTCASES>
</TESTSUITE>