An Object-Oriented Database from AT&T which extends C++ and supports fast queries, complex application modelling and multimedia.

Ode uses one integrated data model (C++ classes) for both database and general purpose manipulation. An Ode database is a collection of persistent objects. It is defined, queried and manipulated using the language O++. O++ programs can be compiled with C++ programs, thus allowing the use of existing C++ code. O++ provides facilities for specifying transactions, creating and manipulating persistent objects, querying the database and creating and manipulating versions.

The Ode object database provides four object compatible mechanisms for manipulating and querying the database. As well as O++ there are OdeView - an X Window System interface; OdeFS (a file system interface allowing objects to be treated and manipulated like normal Unix files); and CQL++, a C++ variant of SQL for easing the transition from relational databases to OODBs such as Ode.

Ode supports large objects (critical for multimedia applications). Ode tracks the relationship between versions of objects and provides facilities for accessing different versions. Transactions can be specified as read-only; such transactions are faster because they are not logged and they are less likely to deadlock. 'Hypothetical' transactions allow users to pose "what-if" scenarios (as with spreadsheets).

EOS, the storage engine of Ode, is based on a client-server architecture. EOS supports concurrency based on multi-granularity two-version two-phase locking; it allows many readers and one writer to access the same item simultaneously. Standard two-phase locking is also available. Ode supports both a client-server mode for multiple users with concurrent access and a single user mode giving improved performance.

Ode 3.0 is currently being used as the multimedia database engine for AT&T's Interactive TV project. Ode 2.0 has also been distributed to more than 80 sites within AT&T and more than 340 universities. Ode is available free to universities under a non-disclosure agreement. The current version, 3.0, is available only for Sun SPARCstations running SunOS 4.1.3 and Solaris 2.3. Ode is being ported to Microsoft Windows NT, Windows 95 and SGI platforms.

E-mail: Narain Gehani <[email protected]>.