capabilities to their standard RDBMS software systems to create hybrid object-relational DBMS (ORDBMS). An ORDBMS can be thought of as an RDBMS engine with an extensibility framework for handling objects. They can handle both the data describing what an object is (object attributes such as color, size, and age) and the behavior that determines what an object does (object methods or functions such as drawing instructions, query interfaces, and interpolation algorithms) and these can be managed and stored together as an integrated whole. Examples of ORDBMS software include IBM DB2 and Informix Dynamic Server, Microsoft SQL Server, and Oracle. As ORDBMS and the underlying relational model are so important in GIS