Various techniques for providing a Web Service interface to an order management system are disclosed. In one embodiment, a Web Service interface receives a hierarchical property set, which includes properties being input to an order management system. The Web Service interface accesses mapping information, which associates a variable in a flat property set with a hierarchical property set path. The Web Service interface uses the mapping information to convert the hierarchical property set to the flat property set, based upon the mapping information, and then causes the order management system to process the flat property set. The Web Service interface can also use the same mapping information to convert a flat property set generated by the order management system into a hierarchical property set.