I am developing a set of classes to process payments for several web sites. I am planning to expose these classes to the web sites as a web service. When I call the web service to process a transaction I would like to pass it a "transaction" object, but I am confused as to how I should develop the project so that the web sites will have knowledge of the transaction object so they can instantiate the object and pass it to the web service? Any help would be greatly appreciated.

Thanks!

Shawn