JavaPolis was my first Drools presentation, in-fact I think THE first public Drools presentation, and had about thirty attendees. The slot allocated to me was a BOF, Birds of a Feather, these are technical sessions for emerging technologies, they are less formal and a good place to cut your teeth. I shared the slot with Bart Strubbe from JCS, who was very charming and a great chaperone being a JavaPolis veteran.

I didn't have time to prepare a presentation on drools SMF, Semantic Module Framework, which enables developers to write DSLs, Domain Specific Languages, as I need to work on a suitable example to demo this technology; so instead I concentrated my efforts on explaining the underlying technologies to Drools and the reason for using a rules engine.

Using XML Spy to write the rules, demonstrating how the Drools schema files can be used for a semi-RAD environment, I took the attendees through increasingly complex rules showing how to write the rules and the underlying Rete via GraphViz. This started off with a single condition rule and finished off with a more complex rule demonstrating node sharing. I then covered the Drools architecture talking about the individual modules and how they work together briefly talking about the SMF and DSLs - answering questions along the way. This was complemented with Bart's practical talk on how Drools is used and deployed by JCS and finally a walk through of the Pet Store example.

I knew it would be hard to explain Rete, even with walk through code and diagrams so I allowed free asking of questions - this I think was a mistake as some attendees really couldn't get it and my mistake was to spend too much time answering their questions in an attempt to help them make the mental paradigm shift, this took up too much valuable time which could have been better spent talking about the SMF.

For my next presentation I will spend less time explaining Rete, simply providing a bulleted list of advantages and maybe a handout for those interested, and spend more time on SMF, DSLs and applied techniques.

The slides from the presentation are available to download:
ppt.zip
pdf