8:00 – 4:00 CSIP

• Drools JBoss Rules 5.0 Developer’s Guide
• It is not only difficult to represent business logic in a imperative programming style language, but also hard to differentiate between code that represents the business logic and the infrastructure code that supports it.
• We declare rules in pretty much the same way as the business analyst does the requirements—as a group of if-then statements. The rule engine can then take these rules and execute them over our data in the most efficient way. Rules, which have all of their conditions true, have their then part evaluated. This is different from imperative style programming languages where the developer has to specify how it needs to be done explicitly (with a sequence of conditionals and loops).
• rule represents one requirement. This is more readable and maps to business requirements more naturally.
• Well, having the right resource makes a difference. I have compiled and run a simple set of rules against multiple objects!
• eval is a catch-all solution. It allows execution of any Java/MVEL code (according to the selected dialect) that returns true or false. It should be used only as a last resort when all other options have failed. This is because the rule engine cannot optimize eval. The expression is evaluated every time there is a change in the current rule’s condition (a fact is added, modified, or removed). They don’t have to return time-constant values. Writing eval as the last condition in a rule is a good practice.
• How to get a reference to the current class being evaluated: $a:Account ( balance < 100, name != “Ted”). The ‘$’ is convention and not required

Lunch meeting to go over Noveta changes

8:00 – 8:30 FP

• Tried running the hand code on my laptop but ran into DLL problems. It was the debug version, so I recompiled the release version today. Let’s see if that makes it easier.
• A useful page explaining all this, including that debug dlls are not redistributable.

8:30 – 4:30 CSIP

• Ok, now that I’ve got the examples compiled and running (In Swing! How quaint), let’s see how to use this thing.
• Chapter 2. Use cases and examples
• Sent Ed a status update
• Ok, I got the Drools Developer’s Cookbook, and it looks like I was doing this in the wrong order. Going to start over with the rules engine (Expert)
• Chapter 1. The Rule Engine
• An object type constraint plus its zero or more field constraints is referred to as a pattern. When an inserted instance satisfies both the object type constraint and all the field constraints, it is said to be matched.
• Downloaded drools-distribution-5.3.0.Final, which contains example code. Some problems compiling, but the HelloWorld works, so we won’t worry for now…
• This process is called inference, and it’s essential for the working of a Stateful Session. Stateless Sessions typically do not use inference, so the engine does not need to be aware of changes to data. Inference can also be turned off explicitly by using the sequential mode.