This page shows how the user can play as a teacher to help the NBA (short for Nondeterministic Büchi Automata) learner based on the periodic FDFA learning to learn the language {a, b}^* b^ω.

The user needs to use following command line to play with roll.

java -jar ROLL.jar play -periodic

To start the learning procedure, ROLL will ask you to initialize the alphabet of the target language. In this case, we set the alphabet to {a, b}. Note that for simplicity, we only use the letters from 'a' to 'z'.

Please input the number of letters ('a'-'z'): 
2
Please input the 1th letter: 
a
Please input the 2th letter: 
b

At the beginning, the learner has to initialize and close the observation tables by asking you several membership queries.

 
Is w-word (ϵ, a) in the unknown languge: 1/0
0
Is w-word (ϵ, b) in the unknown languge: 1/0
1
Is w-word (ϵ, ba) in the unknown languge: 1/0
0
Is w-word (ϵ, bb) in the unknown languge: 1/0
1

When the learner constructs a conjectured NBA, it will ask an equivalence query for the conjecture. In this case, you can answer a counterexample, say (b, ab) since the output automaton is not the right conjecture.

Resolving equivalence query for hypothesis (#Q=4)...  
Is following automaton the unknown automaton: 1/0?
digraph {
  0 [label="0", shape = circle];
  0 -> 0 [label="b"];
  0 -> 2 [label="b"];
  0 -> 3 [label="b"];
  0 -> 0 [label="a"];
  0 -> 1 [label="a"];
  1 [label="1", shape = circle];
  1 -> 2 [label="b"];
  1 -> 3 [label="b"];
  1 -> 1 [label="a"];
  2 [label="2", shape = circle];
  2 -> 2 [label="b"];
  2 -> 3 [label="b"];
  2 -> 1 [label="a"];
  3 [label="3", shape = doublecircle];
  3 -> 2 [label="b"];
  3 -> 1 [label="a"];
  4 [label="", shape = plaintext];
  4 -> 0 [label=""];
}
0
Now you have to input a counterexample for inequivalence.
please input stem: 
b
You input a stem: b
please input loop: 
ab
You input a loop: ab

The learner will ask several membership queries in order to analyze the received counterexample and to construct a new conjecture.

Is w-word (b, ab) in the unknown languge: 1/0
0
Is w-word (ϵ, ab) in the unknown languge: 1/0
0
Is w-word (ϵ, b) in the unknown languge: 1/0
1
Is w-word (ϵ, b) in the unknown languge: 1/0
1
Is w-word (ϵ, bb) in the unknown languge: 1/0
1
Is w-word (ϵ, ab) in the unknown languge: 1/0
0
Is w-word (ϵ, bab) in the unknown languge: 1/0
0
Is w-word (ϵ, bbb) in the unknown languge: 1/0
1
Is w-word (ϵ, aa) in the unknown languge: 1/0
0
Is w-word (ϵ, aab) in the unknown languge: 1/0
0
Is w-word (ϵ, ab) in the unknown languge: 1/0
0
Is w-word (ϵ, abb) in the unknown languge: 1/0
0

This time we receive the right conjectured NBA and reply with positive answer to the learner, which means that the learner has completed its learning task.

Resolving equivalence query for hypothesis (#Q=3)...  
Is following automaton the unknown automaton: 1/0?
digraph {
  0 [label="0", shape = circle];
  0 -> 0 [label="b"];
  0 -> 1 [label="b"];
  0 -> 2 [label="b"];
  0 -> 0 [label="a"];
  1 [label="1", shape = circle];
  1 -> 1 [label="b"];
  1 -> 2 [label="b"];
  2 [label="2", shape = doublecircle];
  2 -> 1 [label="b"];
  3 [label="", shape = plaintext];
  3 -> 0 [label=""];
}

1
Congratulations! Learning completed...

Following command allows the user to see more details about the storage of the membership queries.

java -jar ROLL.jar play -periodic -v