[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message] Re: XPath/XSLT 2.0 concerns
Aaron Skonnard wrote: > How well the "back end" deals with exceptional conditions is > implementation dependent. For example, if you write a Web service in > .NET like this: > > [WebMethod] > public double Add(double x, double y) { > return x+y; > } > > It expects an Add element with two child elements, x and y. If, however, > you send it an Add element with foo and bar child elements, or no child > elements, or something else off the wall, it will happily return 0. This > is a false positive, where most developers would expect an exception. > Performing schema validation before the method is called moves such > error handling down a layer and protects you from this type of thing > happening. There are some controversial design choicesin the above, but the argument for schema validation because it pushes some things down a layer does have some merit. But I don't buy it. If I'm going to be accepting transactions encoded in XML my *business* level validation is going to be doing a lot of looking up part numbers in catalogues and buyer-IDs in other databases and pricing rules and so on and so on. If I'm already doing this in a high-volume transaction processing application I think it's going to be hard to justify a full-dress schema validation step when the business-validation code already knows the data types and can do the data conversion right down there inline, and fail deterministically if something isn't as expected. -Tim
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