make generic dynamic epistemic logic system in csharp

main.cs
public abstract class Agent { }

public abstract class Proposition { }

public class EpistemicState {
    public Agent Agent { get; set; }
    public HashSet<Proposition> Propositions { get; set; }
}

public abstract class Update {
    public Agent Agent { get; set; }
    public abstract EpistemicState UpdateState(EpistemicState state);
}

public class Model {
    public HashSet<EpistemicState> States { get; set; }
    public Dictionary<Agent, HashSet<EpistemicState>> AgentStates { get; set; }
}
501 chars
19 lines

main.cs
public static bool IsKnownBy(this Agent agent, Proposition proposition, Model model, EpistemicState state) {
    foreach (var world in model.States) {
        if (world.Agent == agent && world.Propositions.Contains(proposition)) {
            foreach (var otherWorld in model.States) {
                if (otherWorld.Agent == agent && state.Propositions.IsSubsetOf(otherWorld.Propositions)) {
                    return true;
                }
            }
        }
    }
    return false;
}
494 chars
13 lines