JACK——BOM Exercise4
Use a beliefset callback method.
In this exercise you add an order beliefset to your Planner agent and use a beliefset callback method to post a FindSubcomponent event to the agent. This will result in a list of subcomponents being printed for the required new component.
1. Use the JDE to create a new beliefset type called Orders that belongs to the bom package. It will have one key field (String orderId) and three non-key fields (String component, int numberRequired, String date). Add at least one query to the beliefset.
2. Open the Planner_AD design diagram and
- Drag a new named data component from the design palette onto the design diagram canvas. Call the named data orders and set its type to be bom.Orders.
- Create a private link from the Planner agent to the orders named data.
3. Modify the Planner agent so that it contains a new method addOrder(String orderId, String component, int numberRequired, String dueDate) that will add a new order into the orders beliefset. Note that the add() method may throw a BeliefSetException, so add must be invoked from inside a try/catch block. You will also need to import aos.jack.jak.beliefset.BeliefSetException. Your addOrder() method should be similar to the following:
public void addOrder(String id, String comp, int n, String dd)
{
try {
orders.add(id,comp,n,dd);
}
catch (BeliefSetException e) {
System.err.println("error entering data in orders db");
System.exit(1);
}
}
4. Edit the Orders beliefset type and
- add a #posts event FindSubcomponent ev; declaration;
- Add an indexed query that accepts the order ID (String), component type (logical String), number of components required (logical int) and the order date (logical String).
- Add a newfact callback to the orders beliefset. Each time a new fact is added to the beliefset, the callback will print a trace message to indicate that a new order has been added to the beliefset and then post a FindSubcomponent event. An example of a beliefset that includes a newfact callback can be found in the Politician example in the introductory notes.
5. Modify the main program so that it:
- includes the following import statement:
import java.util.*;
- no longer invokes the Planner agent's findSubcomponent method;
- no longer exits; and
- reads in the order data from a datafile and invokes the Planner agent's addOrder method to add the details to the beliefset. Sample code for this follows:
StringTokenizer tokens;
String record;
String t1,t2,t3,t4;
BufferedReader datafile = null;
Planner planner = new Planner("planner1","bom.dat");
try {
datafile = new BufferedReader(new FileReader("orders.dat"));
}
catch (FileNotFoundException e) {
System.err.println("unable to open file "+e.toString());
System.exit(1);
}
try {
while ( (record = datafile.readLine()) != null ) {
tokens = new StringTokenizer(record);
t1 = tokens.nextToken();
t2 = tokens.nextToken();
t3 = tokens.nextToken();
t4 = tokens.nextToken();
planner.addOrder(t1,t2,Integer.parseInt(t3),t4);
}
}
catch (Exception e) {
System.err.println("error reading orders data ");
System.exit(1);
}
6. Create a data file that contains several orders. At least one order should be for a component that has four or more subcomponents.
7. Compile and run the program.
运行结果
(1) a1 added to orders db:
(2) chair 10 30/01/05
(3) a2 added to orders db:
(4) table 50 20/02/05
(5) a3 added to orders db:
(6) cupboard 60 20/03/05
(7) seat is a subcomponent of chair
(8) back is a subcomponent of chair
(9) arm is a subcomponent of chair
(10) leg is a subcomponent of chair
(11) leg is a subcomponent of table
(12) top is a subcomponent of table
(13) cabinet is a subcomponent of cupboard
(14) door is a subcomponent of cupboard
(15) leg is a subcomponent of cupboard
(16) drawer is a subcomponent of cupboard
运行结果分析
在main方法中调用Planner Agent的初始化方法，读取bom.dat的数据文件，形成BOM信念集。读取文件orders.dat的数据文件，通过add（）方法，添加形成Orders的信念集，add（）方法会自动触发Orders信念集的newFact（）方法，获取元组信息，打印输出（1）、（2）、（3）、（4）、（5）、（6），并触发FindSubcomponent事件（InferenceGoalEvent-执行所有可应用的规划，以及一个规划的所有可能的绑定实例），比如第一个是chair，那么查找chair的所有子部件，输出（7）、（8）、（9）。后面的类似。