The COCOON project was intended to extend the concepts and the architecture of relational database management systems (DBMSs) beyond nested relational to object-oriented ones. Based upon the nested relational DBMS kernel DASDBS, we have built a prototype implementation of the COCOON model. Key characteristics of COCOON are: generic, set-oriented query and update operators similar to relational algebra and SQL updates, respectively; object-preserving semantics of query operators, which allows for the definition of updatable views; a separation of the two aspects of programming language "classes": type vs. collection; predicative description of collections, similar to "defined concepts" in KL-One--like knowledge representation languages; automatic classification of objects and views (positioning in the class hierarchy); physical clustering of subobjects via the use of nested relations as the internal storage structures; support for the optimization of both, the physical DB design and query transformation, by corresponding optimizers.
Project goals are:
- to develop a general formal framework for investigations of all kinds of schema changes in object-oriented database systems (including schema design, schema modification, schema tailoring, and schema integration); - to find implementation techniques for evolving database schemas, such that changes on the logical level propagate automatically to adaptations of the physical level (without the need to modify all instances, if possible).
In their current paper [see below], schema evolution is used as example of a general framework for change in OODBs, supporting change on three levels of database objects: data objects, schema objects, and meta-schema objects.
Contact: Markus Tresch <firstname.lastname@example.org>
REFERENCES: M. Tresch and M.H. Scholl. "Meta Object Management and its Application to Database Evolution." In _Proceedings of the Eleventh International Conference on the Entity-Relationship Approach", Karlsruhe, Germany, Oct 1992. Springer Verlag (to appear).
> Encore (Brown University) email:email@example.com
Encore is an object-oriented database system targeted at large scale software engineering applications which are involved in data modeling. It was developed at Brown University in the late 1980s. It is notable for its special support for long-lived (ie. cooperative) transactions, popular in design applications, and its support for class versioning. Objects are never converted, rather, classes are versioned, and the user can specify filters to make old-style instances appear as new instances to new applications (and vice versa).
 Mary F. Fernandez. OBSERVER: A storage system object-oriented applications. Technical Report CS-90-27, Brown University, Providence, RI, 1990.
 Mark F. Hornick and Stanley B. Zdonik. A shared, segmented memory system for an object-oriented database. ACM Transactions on Office Information Systems, 5(1):70--95, January 1987.
 Andrea H. Skarra and Stanley B. Zdonik. Type evolution in an object-oriented database. In Research Directions in Object-Oriented Programming, MIT Press Series in Computer Systems, pages 393--415. MIT Press, Cambridge, MA, 1987. An early version of this paper appears in the OOPSLA '86 proceedings.
 Andrea H. Skarra and Stanley B. Zdonik. Concurrency control for cooperating transactions in an object-oriented database. In Won. Kim and Frederick H. Lochovsky, editors, Object-Oriented Concepts, Databases and Applications. Addison-Wesley, Reading, MA, 1989.
FTP: Complete source can be found in wilma.cs.brown.edu/pub/encore.tar.Z See also APPENDIX E.
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