Now it is impossible to use pure XMLDB:API for embedded
database.
But, there is workaround:
In case of connecting to embedded database, I manually
create xmldb:api Collection
[com.dbxml.db.client.xmldb.CollectionImpl] basing on
local dbXMLClient
[com.dbxml.db.client.local.dbXMLClientImpl].
To enable pure XMLDB:API I offer
to make existdb-like url naming convention - if url
starts with "dbxml:///" then use embedded database and
local dbXMLClient.