Another aspect not really mentioned in the 'pro web 2 dev' book is the concept of business logic and rules and how they should be handled in the next generation of applications- we need a fundamentally new way to build apps that allow every tier to respond rapidly to business changes, that allow users to change or define business logic. How do we architect such apps; which technologies should we use? Traditional design patterns like 'domain-model' and the naive 'active-record' are woefully inadequate. SOA patterns and related technologies and approaches (e.g. BPML, rules-engines, workflow) seem to either solve very large-scale problems(SOA implementations in e.g. websphere or Bizztalk) or very specific problems (e.g. rules engine for insurance app or trading platform)or they are overlapping and confusing. But every single app stiil have that costly maintenance problem- web 2 or not. I've tried full-fledged SOA tools like Ofbiz (with it's services engine) that are very scalable, but far too unproductive and on other extreme: Ruby-onRails that are (except for UI) very productive, but doesn't scale well: meaning that once you are in the thousands of lines of application code, business logic becomes hard to maintain, because active record works best with basic CRUD or simple logic only. Any thoughts?