As said in the “rule of numb” post, test your statement before you build an XMLIndex (structured or unstructured) on you column or table XML store. The database will check on the syntax you will use but NOT on the outcome. So if you statement doesn’t have the proper result set or is even empty, than the content table(s) or path table will be indexing the wrong element values or even a null data set. Be aware that XML in Oracle is case-sensitive and critical on calling a namespace reference if one if demanded by the W3C rules.
The following example will build a single structured XMLIndex on a binary xml column.
Its time to get rid of some backlog about Oracle 11gR2 XML DB features. Ones of them is about the new Structured XMLIndex or also called XMLIndex Structured Component. So in Oracle 11gR2 you have the ability to use a “unstructured” XMLIndex (UXI) and a “structured” XMLIndex (SXI). The use cases for these global index types specially designed for the XML DB realm are described in the Oracle XMLDB Developers Guide for 11gR2 and in short are show in the following picture.