How does XDB optimize XML Query?

Question

I found the query speed of XDB is much slower than Berkeley XML DB.
How does XDB optimize XML Query?
Are there any documents on this subject?
And can XDB create indices on XMLType ( e.g. the index on element/attribute value and/or structure index)? if yes, how to do that?

Answer 1

lezhou had a valid question and asked about:
"I found the query speed of XDB is much slower than Berkeley XML DB"
"How does XDB optimize XML Query?"
These point to a "XML DB Concepts Guide", which does not yet exist.
The procedures are explained, the methods are explained. If you enable event tracing as described in the XMLDB Developers Guide 10gR2, you will see statements in your trace file which will tell you more about the XML DB architecture (and therefor you can deduct performance impact) then the manual will reveal.
An other example:
The xdbconfig.xsd file is neatly explained - in regards of http-port-etc
But not what the implecations are if you alter one of the other ones (the not explained parameters).
If you know the architecture (GROUND LEVEL), you can give an correct answer to the initial question "I found the query speed of XDB is much slower than Berkeley XML DB. How does XDB optimize XML Query?"
The balanced tree index is constructed the same way (on the same theory) in Oracle, DB2, but apparantly X is faster because in with the same buildup/architecture/databasestructure for both products, with the same data, with the same X --> value Y is beter constructed and delivers a better performance.
apples = apples
oracle xmldb = berkeley xmldb --> how can i test the o.apples=b.apples and that under these circumstances o.apples are faster ;-)
THEREFOR:
"I have to disagree a little bit...("It speaks about all these in detail").
Still waiting for the XMLDB Concepts Guide / Administrators Guide / Performance Guide.