query registered xmlschema xmltype data

I am new to xml db and   having problem extracting the data from xmltype column:

I did the following steps

1. Create XML SCHEMA

BEGIN -- Delete the schema, if it already exists; otherwise, this produces an error. -- Delete the schema, if it already exists; otherwise, this produces an error. DBMS_XMLSCHEMA.deleteSchema ( ( 'http://www.example.com/schemas/parameter.xsd', 'http://www.example.com/schemas/parameter.xsd', 4 4 ); END; /

); END; / BEGIN -- Register the schema -- Register the schema DBMS_XMLSCHEMA.registerSchema ( ( 'http://www.example.com/schemas/parameter.xsd', 'http://www.example.com/schemas/parameter.xsd', '<schema targetNamespace="http://www.example.com/IPO