top down approach vs bottom up approach in programming code example

Example: top down vs bottom up approach

Top down SOAP Web services include 
creating WSDL(Web Services Description Language) 
document to create a 
contract between the web service and
the client, with a required code as
an option. This is also known as 
Contract-first approach. The top-down
approach is difficult to implement 
because classes must be written to 
confirm the contract defined in WSDL. 
One of the benefits of this method is
that both client and server code can
be written in parallel.
Bottom up SOAP web services require 
the code to be written first and then
WSDL is generated. It is also known
as Contract-last approach. Since WSDL
is created based on the code, bottom-up
approach is easy to implement and client
codes must wait for WSDL from the server
side to start working.