We developed schema and tuple trees in 1989 when we first developed Qddb. At that time, Qddb was implemented in around 10,000 lines of C code and performed very basic searches and operations. Qddb was released to the public, but the presentation utilities were so crude that only a few hundred people bothered to learn about it. Qddb development stalled until 1994 because of other projects. In 1994, we began building a generic graphical application based on the schema tree. With the advent and maturation of Tcl and the Tk toolkit [Ousterhout 1994], we have been able to build a significantly improved interface that interacts with the X Window System [Scheifler & Gettys 1986].
Today, Qddb sports a fancy graphical user interface allowing users to conveniently navigate and search for rows in tuple trees. As a result, the Qddb user community has grown to thousands of people world-wide. Applications include World-Wide Web (WWW) servers, inventory management, client-invoice management, point-of-sale terminals, experimental data analysis, project tracking, bug reports, journal abstracts, dictionaries, and student records.
Qddb is implemented in around 45,000 lines of C and Tcl code. It runs on any Unix-based computer. Qddb is always publicly available from:
ftp.ms.uky.edu:pub/unix/qddb/qddb-<version>.tar.gz
The distribution contains full documentation and source. Sample databases and applications are also available.