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implement the concrete services and bindings. With the Top-Down approach, both teams can
work somewhat concurrently, with little overlap of work.
The Bottom-Up approach
With the Bottom-Up approach, you use a collection of services that you already have available
(perhaps, within an enterprise repository in your organization) to build out a service compos-
ition. You already have complete and valid WSDLs, and you want to combine existing func-
tionality to make something new.
Of course, this approach only works when you have a large variety of services available that
you can combine to create a new process. You may find that if you have designed services
at an appropriate level of granularity within your organization, you can find new uses for ex-
isting services within compositions. For example, a service that is used to capture customer
signatures in a retail store could also be used in designing a service for new hires who have
extensive paperwork to fill out.
The Meet in the Middle approach
This approach combines the qualities of the previous two techniques. This is typically most
realistic once you have developed several services or have a business partner whose services
you subscribe to. In general, you can accept a workflow from a designer and create service
interfaces with stub implementations; this allows you to work concurrently. The analyst can
fine tune the process while you implement the services.
