The most basic scenario fulfilled by XML Web services is that of providing some fundamental piece of functionality for its clients to use. For example, a challenge faced by e-commerce applications is the need to calculate charges for an assortment of shipping options. Such applications would require current shipping cost tables from each shipping company to use in these calculations.
Alternatively, an application could send a simple XML-based message over the Internet, using a standard transport protocol such as HTTP, to the shipper's cost calculation XML Web service. The message might provide the weight and dimensions of the package, ship-from and ship-to locations, and other parameters, such as class of service. The shipper's XML Web service would then calculate the shipping charge using the latest cost table, and return this amount, in a simple XML-based response message, to the calling application for use in calculating the total charge to the customer.