Bayesian Network

This repository contains an academic project implementing Bayesian network inference in Java. The goal was to create a small inference engine capable of reading a network description in BIFXML format, processing probabilistic queries and producing the resulting probabilities.

Features

• Load Bayesian networks from XML files. Example networks are provided (alarm_net.xml, big_net.xml, family.xml).
• Support for calculating joint probabilities as well as conditional probabilities using three elimination methods.
• Basic counters to track the number of sum and product operations during inference.
• Includes a TestFactor class with unit tests for the Factor operations (requires JUnit 5).

Project Structure

├── src/                 # Java source files
│   ├── BayesNet.java    # Core inference engine
│   ├── Counter.java     # Operation counters
│   ├── Ex1.java         # Runner that reads queries from `input.txt`
│   ├── Factor.java      # Factor representation and operations
│   ├── InteractionGraph.java
│   ├── Variable.java
│   ├── VariableOutcome.java
│   └── TestFactor.java  # JUnit tests for Factor (optional)
├── alarm_net.xml        # Example network
├── big_net.xml          # Example network
├── family.xml           # Example network
├── input.txt            # Example input file with queries
└── output.txt           # Example output produced by Ex1

Running

1. Ensure you have a Java compiler (tested with javac 1.8) available in your PATH.
2. Compile the project:

javac src/*.java

3. Place the network file you want to use and the queries in input.txt. The first line of input.txt should be the path to the XML file followed by one query per line. Queries have the form P(X=Y|Z=W),<method> where <method> is 1, 2 or 3 for the different elimination approaches.
4. Run the program:

java -cp src Ex1

The results are written to output.txt in the format <probability>,<sumCount>,<productCount> where the counts reflect how many summation and multiplication operations were performed.

Running the Tests

The TestFactor class provides JUnit tests for the Factor class. To execute them you need JUnit 5 on your classpath. For example:

# assuming junit-platform-console-standalone.jar is downloaded
javac -cp junit-platform-console-standalone.jar src/*.java
java -jar junit-platform-console-standalone.jar -cp src --scan-classpath

License

This project was created as part of a university assignment and is provided for educational purposes.