Isn't XSLT only meant to access one document at a time?

• The source tree data model extends the XPath model to allow multiple root elements, text, etc. at the top-level. One approach could be to logically concatenate in some order all the documents in the XML repository into this one tree. Then, for example, /foo would access every root element whose name is "foo".
• Some problems with this approach:
  • Retaining document identity is important for the id() function, among other things.
  • For example, you may wish to return the entire document, including processing instructions and comments, even though you don't know the document's name (and thus can't access it via the document() function.)
  • Ultimately, this is also (at least currently) a problem for XQuery, which in one place states, "A query can also contain a path expression beginning with '/' or '//' which represents an implicit root node, determined by the environment in which the query is executed." Yet, in another place, it says, "In XQuery, '/' denotes the root of the document of the current node." It can't be both, so which is it?