Software
Links
BayesBuilder
http://www.snn.ru.nl/nijmegen/index.php3?page=31
A tool for constructing and testing Bayesian networks.
BayesiaLab
Bayesian network laboratory producing a broad set of tools for structure learning, analysis, adaptive questionnaires, and dynamic Bayesian networks
Bayesian Belief and Decision Networks Applet
http://www.cs.ubc.ca/labs/lci/CIspace/version2/bayes.html
CISpace tools for learning about belief networks: a set of Java applets and example networks.
Bayesian Knowledge Discoverer
http://kmi.open.ac.uk/projects/bkd/
Able to learn Bayesian Belief Networks from (possibly incomplete) databases. Algorithm based on the Bound and Collapse estimation method.
Bayesian Network Toolbox (BNT)
http://www.ai.mit.edu/~murphyk/Software/BNT/bnt.html
Kevin Murphy's MATLAB toolbox - supports dynamic BNs, decision networks, many exact and approximate inference algorithms, parameter estimation, and structure learning
Bayesian Network tools in Java (BNJ)
Open-source suite of software tools for research and development using graphical models of probability, published by Kansas State University Laboratory for Knowledge Discovery in Databases (KDD)
Bayesline
http://bayesline.sourceforge.net
Very generic and free (LGPL) Belief Network Framework in C++ - supports a broad range of knowledge and dependency types for network variables and clusters of variables
Belief Net Power Constructor
http://www.cs.ualberta.ca/~jcheng/bnpc.htm
System based on Jie Cheng's three-phase belief network construction algorithm. Includes a wizard-like user interface and a belief network construction engine.
BUGS - Bayesian inference Using Gibbs Sampling
http://www.mrc-bsu.cam.ac.uk/bugs/
Bayesian analysis of complex statistical models using Markov chain Monte Carlo (MCMC) methods.
CleverSet, Inc.
Develops and exploits proprietary Relational Bayesian Modeling (RBM) technology and applications that provide real-time, actionable results from large amounts of dynamic, multi-faceted, ambiguous information.

