java 决策树和规则引擎（Drools）
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Decision trees and rule engines (Drools)
提问by John Manak
In the application that I'm working on right now, I need to periodically check eligibility of tens of thousands of objects for some kind of a service. The decision diagram itself is in the following form, just way larger: 
在我现在正在处理的应用程序中，我需要定期检查数以万计的对象是否符合某种服务的资格。决策图本身采用以下形式，只是更大一些：
In each of the end nodes (circles), I need to run an action (change an object's field, log information etc). I tried using Drool Expert framework, but in that case I'd need to write a long rule for every path in the diagram leading to an end node. Drools Flow doesn't seem to be built for such a use case either - I take an object and then, depending on the decisions along the way, I end up in one of the end nodes; and then again for another object. Or is it? Could you give me some examples/links to such solutions?
在每个端节点（圆圈）中，我需要运行一个操作（更改对象的字段、日志信息等）。我尝试使用 Drool Expert 框架，但在那种情况下，我需要为图中通向终端节点的每条路径编写一条长规则。Drools Flow 似乎也不是为这样的用例构建的——我拿了一个对象，然后，根据沿途的决定，我最终到达了一个终端节点；然后再次为另一个对象。或者是吗？您能给我一些此类解决方案的示例/链接吗？
UPDATE:
更新：
Drools Flow calls might look like this:
Drools Flow 调用可能如下所示：
// load up the knowledge base
KnowledgeBase kbase = readKnowledgeBase();
StatefulKnowledgeSession ksession = kbase.newStatefulKnowledgeSession();
Map<String, Object> params = new HashMap<String, Object>();
for(int i = 0; i < 10000; i++) {
Application app = somehowGetAppById(i);
// insert app into working memory
FactHandle appHandle = ksession.insert(app);
// app variable for action nodes
params.put("app", app);
// start a new process instance
ProcessInstance instance = ksession.startProcess("com.sample.ruleflow", params);
while(true) {
if(instance.getState() == instance.STATE_COMPLETED) {
break;
}
}
// remove object from working memory
ksession.retract(appHandle);
}
That is: I'd take an Application object, start a new process for it, when the process is finished (the final, action node would modify the application somehow), I'd remove the object from working memory and repeat the process for a new App object. What do you think about this solution?
那就是：我会拿一个 Application 对象，为它启动一个新进程，当进程完成时（最终的动作节点会以某种方式修改应用程序），我会从工作内存中删除该对象并重复该过程一个新的 App 对象。你怎么看这个解决方案？
SOLUTION:
I've ended up using Drools Flow and it has been working quite fine. My decision process isn't as straightforward as Drools Expert asks for and depending on where in the decision tree the process is it needs to load lists of objects from the database, transform them, make decisions, log everything etc. I use a Process object that is passed to the process as a parameter and stores all my global variables (for the process) and some convenience methods that are repeated at different points in the tree (as writing Java code in the Script Tasknodes isn't very convenient itself). I also ended up using Java to make decisions (and not mvelor rules) - it's faster and I'd say easier to control. All objects that I work with are passed as parameters and used as normal Java variables in the code.
解决方案：
我最终使用了 Drools Flow，它运行良好。我的决策过程并不像 Drools Expert 要求的那么简单，并且取决于决策树中的哪个过程需要从数据库加载对象列表、转换它们、做出决策、记录所有内容等。我使用 Process 对象它作为参数传递给进程并存储我的所有全局变量（用于进程）和一些在树中不同点重复的便捷方法（因为在Script Task节点中编写 Java 代码本身并不是很方便）。我也最终使用 Java 来做出决定（而不是mvel或规则）——它更快，我会说更容易控制。我使用的所有对象都作为参数传递并用作代码中的普通 Java 变量。
回答by Geoffrey De Smet
Drools expertis definitely the way to go.
Drools专家绝对是要走的路。
If you want to avoid repeating yourself for the higher nodes, then the trick is to use insertLogical(or just insertif you're in a stateless session) and to understand that rules can trigger rules (It's not your father's SQL query). For example:
如果您想避免在更高的节点上重复自己，那么诀窍是使用insertLogical（或者只是insert如果您处于无状态会话中）并了解规则可以触发规则（这不是您父亲的 SQL 查询）。例如：
// we just insert Customer objects in the WM
rule "evaluateRetired"
when
$c : Customer(age > 65)
then
insertLogical(new Retiree($c));
end
rule "evaluteRetireeIsFemale"
when
$r : Retiree(customer.gender == Gender.FEMALE, $c : customer)
then
...
end
If the decision diagram frequently changes (and you want non-programmers to edit it), take a look at the documentation on decision tables(and DSL). In that case you'll probably repeat the entire path for each rule, but that's actually ok in most cases.
如果决策图经常更改（并且您希望非程序员对其进行编辑），请查看有关决策表（和DSL）的文档。在这种情况下，您可能会为每个规则重复整个路径，但在大多数情况下这实际上是可以的。
回答by supercoco
I had a similiar problem and used Neo4J node database as a simple and very flexible rules engine. You can use is it with a REST service interface so it is independent from the main application. You can also have a separate application to configure the rules (even by end users).
我有一个类似的问题，使用 Neo4J 节点数据库作为一个简单且非常灵活的规则引擎。您可以将它与 REST 服务接口一起使用，因此它独立于主应用程序。您还可以使用单独的应用程序来配置规则（甚至由最终用户）。
回答by Sid
You can try the iLog framework cum rules engine.
您可以尝试 iLog 框架和规则引擎。
