Expert System Design Funadmentals - HowTo?

Hi Experts,

I am looking at designing an Expert System. I have done some looking around and it seems that most examples of expert systems drill down to a single goal.

For example:
- Whale watcher (http://www.aiinc.ca/demos/whale.html)
- Medical (http://easydiagnosis.com/cgi-bin/expert/thorask/thorask.cgi)
- Financial (http://www.myacquire.com/aiinc/stock/rds.asp)
- Car won't start (http://www.expertise2go.com/webesie/tutorials/ESIntro/)

I find myself in the role of "Knowledge Engineer" as it is described towards the end of this wiki (http://en.wikipedia.org/wiki/Expert_system).

So, I'm out of my depth - again - in a major way :-)

In short there is no 'single' answer for my application. The output of the expert system should look something like this:

"Cause A"  seems to be your main problem, we suggest trying the following...
"Cause D" and "Cause F" seem to be contributing factors... we suggest checking...


We have 6 Major categories - I would generally expect 2 to 3 of these to be implicated as Cause of a problem and with 1 being a clear "main cause".

The recommendations are based on sub-categories... so for each category we need to drill down further to determine the sub-causes... (I think this makes sense...).

So, questions:

* How can I best structure my information?
* Do I use Forward or Reverse chaining?
* Is there a generic template available where I can test my own data tables?
* Should I ask questions 1 at a time or in groups?
* Should I ask yes not questions or also include option lists?
* What is a small/large data set (I envisage ~100 If-Thens)
* Is there a download that I can just plug in my data without having to create a whole ES?

Any advice greatly appreciated - many thanks

Steve