sth valuable(maybe) about ofbiz framework:
1.ofbiz implemented a powerful flexible and standarlized xml process description schema for its service engine, which named MiniLanguage, that is pretty coooooool!!!
2.its entity engines is good but not the best. it is not very flexible and not extendable too. for exmaple, if you have to execute a very complex query which joined three or more tables and many sql function used, let us to be honest, the entity engines sucks.
3.in ofbiz, the service engine strongly depends on its entity engine. you wanna a seprated service engine withou entity engine?sorry, no way!and i DO hate it!!!
4.i like the service concept! it is extremely nice, clear interface definition and brilliant flow control.
only based on my own opinions :D