[bpel-dev] Is there any useful documents for me to learn about the detai

[grovecai <grovecai@xxxxxxxxx>]

Hello! Everyone.
I need to custom bpel designer to add feature that can drag and drop existing web services from something like a services database to build a partnerLink for the BPEL process. So I try to read the source code to find the place to add that feature. However, I got lost in the complicate  relationship between those classes and their methods.
Is there any useful documents for me to learn about the detail of bpel designer? 
 I need your help. Any hints maybe help. Thank you!

grovecai