bOP: The bivio OLTP Platform
bOP is an open source application development framework primarily focused on information systems. The architecture is layered, so you can use just a little bit, the whole thing, or somewhere in between. bOP has about 900 classes.
The first step is to read why bOP? This will give you a feeling for the problem bOP evolved to solve.
Visit the bOP Pet Shop to see bOP in action.
You can download bOP here: