ASP.NET: web services design methodologies. top-down and bottom-up. what's the difference?

Question

can someone give me a high level overview of these two methodologies? what's the difference between these two and why would you choose one over the other? i would just like a general explanation in your own words as i'm just starting with web services. thanks.

Answer 1

Top down approach requires you to write your own WSDL and XSDs and then create service which follows that WSDL and XSDs. In bottom up approach you first write service code and then WSDL and XSDs. In MS world bottom up is very easy because WSDL and XSDs are generated for you by tools. The first approach is much harder because it has lesser support in tools and because developers are usually not skilled enough to write WSDL (especially with WS-Policies).

Edit: If you write service first or if you have control over client and service you will always use bottom up. If you need to define contract first so that client and service can be implemented and tested separately (usual in big integration projects) you will use top down.

Best regards, Ladislav