Externalized rules and generated code

Another team at the company I'm contracting for just did some of the first work in creating a new system (it will take years to complete, replacing a COBOL system). They did a little performance testing and they were surprised when it reached only 10% of its target performance metric. Ouch.

A lot of what they're doing is rule-based. The rules are created with a tool developed in-house, and code is generated from it.

Aside from this kind of development being less fun (in my opinion anyway), it absolutely scares the hell out of me that this is the kind of performance they've encountered. It's pretty scary even. One of my theories is that none of the data being moved around is strongly typed, so all of that casting (especially with tons of ArrayLists abound) is bad news. I'm not an expert in that area though, and can only repeat what I've read in various performance texts.

I do really think that externalized rules are a good idea. I'm just not entirely convinced that they can be converted into fast, efficient code, and frankly I've not read any research on the topic one way or another.