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Reading Questions, Lecture 10 (10/13)

Papers: Extensible Types, ObjectStore

These two papers represent two ways in which researchers have explored extensibility via the inclusion of objects and a wide range of types into database systems. They represent the so-called Object-Relational Database (ORDBMS) and Object-Oriented Database (OODBMS) approaches, respectively. Today, the ORDBMS approach is widely used and generally regarded as a success, whereas the OODBMS approach is generally considered to have had much less real-world impact (though object persistence via EJB's in Java is arguably inspired by the OODBMS community.)

As you read the papers, consider the following questions:

  1. In what ways do the two approaches solve the same problems? How are they different? Which would you prefer to use?
  2. Why do you think ORDBMSes are widely considered a success, while OODBMSes are not?
  3. What is the interface to operators and access methods in a database system (as described by Stonebrake in the extensible types paper)? Why do these interfaces make the ORDBMS approach particularly easy to implement?
  4. How are joins expressed in ObjectStore?
  5. How does the "memory mapped architecture" in ObjectStore ensure efficient access to persistent objects? How does the system ensure that modifications to objects are written back to disk?

Samuel Madden (madden at csail dot mit dot edu)
Last modified: Sat Oct 9 09:33:46 EDT 2004