Abstract: A method for extracting metadata for plural related objects of different types from a database includes defining a heterogeneous object type as a collection of database objects of different types. Upon a request to fetch a particular heterogeneous object, member objects of the heterogeneous object are fetched from the particular heterogeneous object in a specific order based on the definition of the heterogeneous object's type, such as a valid order for re-creating the particular heterogeneous object. The set of member objects to be fetched can be restricted according to at least one specified filter, which itself may be translated into a second filter according to a type of a member object being fetched. Such translated filters can inherit values from the filter specified in the request for the particular heterogeneous object type, or can have a fixed value of some data type. The extracted metadata can be formatted to recreate the particular heterogeneous object.

Abstract: An XML representation of the metadata for objects in a database system. The XML representation is called SXML. The SXML representations of two objects that belong to the same class of objects may be compared to produce a difference representation that shows the differences between the objects. Database commands that will create or alter objects may be produced from the difference representation, as well as an XML representation of the database commands. In addition to being comparable, SXML representations have the characteristics that a given property of the metadata is expressed in only one way in the representation, that SXML does not describe properties that belong only to particular instances of the object described by the metadata, that SXML describes only properties that the user can specify when creating an object, and that SXML is easy for humans to read, understand, and write.

Abstract: Techniques for transferring objects between database systems. As implemented in a relational database management system, the techniques employ a data transfer mechanism that operates under control of a master table in the RDBMS that is performing the transfer operation. The master table specifies the kind of transfer operation to be performed, a set of objects to be transferred, operations to be performed on the objects as they are being transferred, and filters for selecting a subset of the objects. During execution of the transfer, the transfer mechanism maintains and updates state in the master table such that queries may be made on the master table to determine the current status of the operation and such that the transfer mechanism may restart the operation after it has been stopped either at the request of a client that is performing the operation or because of an error in the transfer.