[Exist-open] xpath query across collections

[<cv...@gm...>]

Hello,

I am using exist 1.1.1 and I am having trouble testing the "query across 
collections" feature.

I am using the java client.   I have defined two nested collections:

collection1: db/a/b/c/d/e1
collection2: db/a/b/c/d/e2

For now collection1 and collection2 contain 1 XML document each.  I am 
trying a simple XPATH query running at context db/a that finds either 
both XML docs, one of them or none based on a simple XPATH query that 
checks the value of an element in the XML file (for example something 
like "//OrbitNumber = 11111". 

 From the docs, it seems like exist should support this type of query.  
Is this possible to accomplish using the Java client?.

Any help would be appreciated.  I am probably missing something simple 
since I just installed it and browsed through the docs.

Another question:  I am planning to look into using exist to manage an 
archive of about 7-8 million XML files, about 15 - 20 K each.  Anybody 
out there that has tried to use it to manage such a large number of XML 
files?  The max tree depth is about 5-6 levels under the document root.

Thank you very much.