If we have trouble writing a new rule or fixing a broken rule, we should first isolate this rule from others. This can be done by commenting out other rules or by extracting the rule to a new file and working there.
The Drools Eclipse plugin has a 'Rete Tree' view. The Rete Tree view is accessible as the second tab of the
.drl editor. It shows the graphical representation of the Rete network (more about it has been discussed in Chapter 12, Performance). Behind the scenes, it compiles the
.drl file and so it can be used to quickly check if the
.drl file is valid. If not, an error is displayed.
If the rule compiles, but it still isn't doing what we want. We can use a debug event listener to see if the expected facts were ...