dbXML Query Engine
==================
Incomplete

All dbXML indexing patterns are transcribed into short codes
representing either their Symbol ID, a N/A, a Wildcard, or a
late-bound name lookup indicator (for attributes).

   Symbol ID range  Description
   ===============  ======================
   -3               Late-bound name lookup
   -2               Wildcard
   -1               Nil (Not Applicable)
   >=0              Valid Symbol IDs

Lookup optimization is performed in the following order.

For Attributes:

   Elem Attr Description
   ==== ==== =======================================
   >=0  >=0  Attribute for Element
   >=0  -2   Wildcard Attribute for Element
   -2   -3   Attribute for Wildcard Element
   -2   -2   Wildcard Attribute for Wildcard Element

For Elements:

   Elem Attr Description
   ==== ==== ================
   >=0  -1   Element
   -2   -1   Wildcard Element

The IndexManager converts these patterns into an Int that
represents the combination of the two shorts and performs table
lookups based on the resulting int. XPath parse trees are
decomposed, and the appropriate indexes to use to perform the
XPath query are retrieved based on a multi-try lookup based on
these ints, specific to generic.


