Skip to main content

Goals in JaKtA

Goals represent the objectives that an agent aims to achieve. In JaKtA, goals drive the agent’s behavior by activating plans that execute actions.

Understanding Goals​

Goals can indicate either something that the agent wants to achieve by finding an appropriate plan, or something that it wants to test (discover), prioritising the consultation of the knowledge base over the execution of plans. Similarly to Jason, JaKtA supports the definition of agents’ initial goals by means of the goals block. Further goals may arise during the execution of the MAS, thus creating a hierarchy of plans to execute in order to fulfill the initial goal.

Defining initial Goals in JaKtA DSL​

In JaKtA, goals are defined as part of an agent’s configuration:

import io.github.jakta.bdi.dsl.agentSystem
agent("Robot") {
    goals { 
        test("batteryLevel")
        achieve("chargeBattery") 
    }
}

In this example, the Robot agent tests the current batteryLevel, and tries to achieve the goal of charging its battery.

Adding Goals Dynamically​

An agent can adopt new goals at runtime based on its current beliefs and environment.

Example: Adding a Goal Dynamically​


mas {
    agent("Explorer") {
        beliefs {
            fact{ "batteryLevel"(80) }
        }
        goals { achieve("exploreTerrain") }

        plans {
            + achieve("exploreTerrain") onlyIf {
                "batteryLevel"(X).fromSelf and (X greaterThanOrEqualsTo 30) and (Y `is` (X - 10))
            } then {
                execute("print"("I'm exploring... Battery level is now", Y))
                update("batteryLevel"(Y).fromSelf) // Simulating battery drain
                achieve("exploreTerrain")
            }
            + achieve("exploreTerrain") onlyIf { "batteryLevel"(X).fromSelf and (X lowerThan  30) } then {
                execute("print"("Charging battery..."))
                update("batteryLevel"(100).fromSelf)
                execute("stop")
            }
        }
    }
}.start()

Expected Output:​

[Explorer] I'm exploring... Battery level is now 70
[Explorer] I'm exploring... Battery level is now 60
[Explorer] I'm exploring... Battery level is now 50
[Explorer] I'm exploring... Battery level is now 40
[Explorer] I'm exploring... Battery level is now 30
[Explorer] I'm exploring... Battery level is now 20
[Explorer] Charging battery...