HaVSA (Have-Saa) is a Haskell implementation of the Version Space Algebra Machine Learning technique described in Tessa Lau's PhD thesis (the link is for a journal version):
Tessa Lau, Steven Wolfman, Pedro Domingos, and Daniel S. Weld, Programming by Demonstration using Version Space Algebra, Machine Learning, 2003. (http://tlau.org/research/papers/mlj01-draft.pdf)
- [VSIntro Introduction to Version Space Algebra]
A number of Version Spaces papers that I've come across are listed here
HaVSA was created by Rogan Creswick
If you're looking for an implementation in Java, you should check out JVersionSpaces