Querying database system to execute stored procedures using abstract data type attributes, retrieving location information of data, sub-data between first and second servers

A database system comprising:

• a first server to analyze queries about a database;
• and
• at least one of second servers coupled to said first server, via a network, to operate said database, including retrieving XML data from said database,
• wherein said second server is configured, upon a first query for XML data indicating attributes of a XML data type, to extract from said database location information of said XML data and to return said location information as a retrieval result to said first server;
• and
• wherein said first server is configured, upon a second query for sub-data included in said XML data, to return information about a structure of XML data to said second server, said sub-data being used for processing;
• and
• wherein said second server is further configured to return to said first server sub-data hierarchically retrieved from said XML data based on said location information of said XML data and said information about the structure of XML data so that said sub-data in said XML data is used for processing, control and database operations subsequent to the retrieval of said XML data.