I am looking to implement (or build as a last resort) a type of survey engine that allows for extensibility and integration into an existing workflow engine.
The sur
Check out Zodiac.NET Survey Engine written in C# ASP.NET. It meets most of your requirement except it defines the questionnaire in XML format. It can persist the answers as XML files on the server. You can also save the answers to any database using its APIs and bind the XML on the fly to the web controls. The nice thing about this engine is that it's a collection of Web Controls. This is a great benefit when you want to integrate it with your existing applications.