XML DB for XML Data Processing
Oracle XML DB is ideal for any application that processes or accesses XML data. Oracle XML DB is suitable for Internet applications, high-performance search applications (such as online libraries), business-to-business (B2B) applications, content management applications, and for interoperability with any other databases. The database user XDB owns all the metadata for managing the Oracle XML DB repository in the database. Oracle XML DB includes DBMS_XDB, a PL/SQL package, to allow resources to be created, modified, and deleted programmatically.
A good place to learn more about using XML DB is Oracle XML DB Developer's Guide 10g.
Installing XML DB
Oracle XML DB can be installed with or without Database Configuration ...