CODESAMPLE

Blackboard - JavaScript

Blackboard JavaScript

The Blackboard pattern is a computational problem-solving approach where multiple independent knowledge sources (agents) operate on a shared data structure (the blackboard) to collectively solve a complex problem. Each agent recognizes patterns in the blackboard’s state and contributes relevant information, triggering other agents in a cycle until a solution is found. This promotes loose coupling and allows for dynamic problem-solving.

The JavaScript implementation uses a central Blackboard object holding the evolving solution. Agent classes define apply methods which modify the blackboard based on their assigned criteria. A Dispatcher manages the agents and orchestrates the process, iteratively applying agents until a solved flag is set on the blackboard. This leverages JavaScript’s flexible object model and favors composition over inheritance, fitting its typical style. Asynchronous operations could easily be integrated within the agents.

// blackboard.js
class Blackboard {
  constructor(initialData) {
    this.data = initialData;
    this.solved = false;
  }

  setData(newData) {
    this.data = newData;
  }

  getData() {
    return this.data;
  }

  isSolved() {
    return this.solved;
  }

  setSolved() {
    this.solved = true;
  }
}

// agent.js
class Agent {
  constructor(name, condition, apply) {
    this.name = name;
    this.condition = condition;
    this.apply = apply;
  }

  shouldApply(blackboard) {
    return this.condition(blackboard.getData());
  }

  apply(blackboard) {
    this.apply(blackboard.getData());
  }
}

// dispatcher.js
class Dispatcher {
  constructor(blackboard, agents) {
    this.blackboard = blackboard;
    this.agents = agents;
  }

  run() {
    while (!this.blackboard.isSolved()) {
      for (const agent of this.agents) {
        if (agent.shouldApply(this.blackboard)) {
          agent.apply(this.blackboard);
          break; // Apply only one agent per cycle
        }
      }
    }
  }
}

// Example Usage:
// problem: Determine if a number is prime
const initialData = 17;
const blackboard = new Blackboard(initialData);

const checkDivisibility = new Agent(
  "DivisibilityChecker",
  (data) => data > 1,
  (data) => {
    for (let i = 2; i <= Math.sqrt(data); i++) {
      if (data % i === 0) {
        blackboard.setData(`Not prime, divisible by ${i}`);
        return;
      }
    }
    blackboard.setData("Prime");
  }
);

const setSolved = new Agent(
  "SolutionSetter",
  (data) => data === "Prime" || data === "Not prime, divisible by",
  (data) => {
    blackboard.setSolved();
  }
);

const dispatcher = new Dispatcher(blackboard, [checkDivisibility, setSolved]);
dispatcher.run();

console.log(blackboard.getData()); // Output: Prime
console.log(blackboard.isSolved()); // Output: true