XMLIndex Value Index on repository

Question

Hello,
I'm still fighting with that peculiar "value index" feature. Unfortunately I cannot really find comprehensive in-depth information on it at all.
Has anyone ever gotten this to work with the repository?
What I have found out so far:
1) When you have an normal table with an XMLType column and an XMLIndex on this column, then the only way to make VALUEIX show up in the EXPLAIN plan is when I write sth. like this:
SELECT rowid FROM exampletable WHERE EXISTSNODE(xmlcolumn,'/xml[leaf="green"]')=1;
2) It does NOT work if I write:
SELECT rowid FROM exampletable WHERE EXTRACTVALUE(xmlcolumn,'/xml/leaf')='green';
For some reason Oracle isn't able to detect it can use the VALUE index in the latter case.
Only PATHIX is used.
3) The type seems to be important. It does NOT work either if I write:
SELECT rowid FROM exampletable WHERE EXISTSNODE(xmlcolumn,'/xml[leaf=green]')=1;
That's OK, though. According to the documentation the value index created by default is for strings only.
4) Now, with the repository, the first thing to note is that you MUST use UNDER_PATH in your query to limit results on the folders you have created an XMLIndex on.
SELECT rowid FROM resource_view
WHERE
EXTRACTVALUE(res,'/r:Resource/r:Contents/xml/leaf,'xmlns:r="http://xmlns.oracle.com/xdb/XDBResource.xsd"')='green'
AND UNDER_PATH(res,'/public')=1
This uses only PATHIX, though. This follows the logic from above which is that EXTRACTVALUE never uses a VALUE index.
5) OK. Let's try EXISTSNODE then:
SELECT rowid FROM resource_view
WHERE
EXTRACTVALUE(res,'/r:Resource/r:Contents/xml[leaf="green"],'xmlns:r="http://xmlns.oracle.com/xdb/XDBResource.xsd"')=1
AND UNDER_PATH(res,'/public')=1
This doesnt use any xml index at all :-(
Why?

Answer 1

I've tried all variants over the last hours to no avail.
Interestingly, Example 5-31 here is nearly the same query I'm doing:
http://download.oracle.com/docs/cd/B28359_01/appdev.111/b28369/xdb_indexing.htm#CHDBGBEG
Unfortunately, they don't give an EXPLAIN plan with that query so I don't know what they think should happen.
Can the VALUE INDEX be used at all with a repository? My case is the simplest one I could think of. My steps:
1) Take any XML DB repository
2) Insert an XML file (for instance with WebDAV, doesnt matter though)
3) Create an XMLIndex with CALL DBMS_XDB_ADMIN.CreateRepositoryXMLIndex(); and DBMS_XDB_ADMIN.XMLIndexAddPath(...)
4) Try to make a simple XMLExists() query
Doesnt work. No VALUE INDEX used. :-(
Is there any way to query the VALUE INDEX of a repository manually in case this is an Oracle bug? I somehow need to make this work,
because the repository is pretty useless otherwise if I can't query it in an efficient manner.