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Comment by maxwellg | Hacker News Reader

I wasn't around for WSDL so please correct me if I am wrong - but the main weakness of WSDL was that no applications were able to take advantage of dynamic service and method discovery? A service could broadcast a WSDL but something needed to make use of it, and if you're writing an application you might as well just write against a known API instead of an unknown one. LLMs promise to be the unstructured glue that can take advantage of newly-discovered methods and APIs at runtime.

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I was unfortunate enough to work with SOAP and WSDL. There was a pipedream at the time of automatically configuring services based on WSDL but it never materialized. What it was very good at (and still has no equal to my mind) was allowing for quick implementation of API boilerplate. You could point a service at the WSDL endpoint (which generally always existed at a known relative URL) and it would scaffold an entire API client for whatever language you wanted. Sort of like JSON Schema but better.

This also meant that you could do things like create diffs between your current service API client and an updated service API client from the broadcasting service. For example, if the service changed the parameters or data objects, deprecated or added functions then you could easily see how your client implementation differed from the service interface. It also provided some rudimentary versioning functionality, IIRC. Generally servers also made this information available with an HTML front-end for documentation purposes.

So while the promise of one day services configuring themselves at runtime was there, it wasn't really ever an expectation. IMO, the reason WSDL failed is because XML is terrifically annoying to work with and SOAP is insanely complex. JSON and REST were much simpler in every way you can imagine and did the same job. They were also much more efficient to process and transmit over the network. Less cognitive load for the dev, less processor load, less network traffic.

So the "runtime" explanation isn't really valid as an excuse for it's failure, since the discovery was really meant more in practice like "as a programmer you can know exactly what functions, parameters, data-objects any service has available by visiting a URL" and much less like "as a runtime client you can auto-configure a service call to a completely new and unknown service using WSDL". The second thing was a claim that one-day might be available but wasn't generally used in practice.

> take advantage of dynamic service and method discovery

Is that how people build system even today? Dynamic service and method discovery sounds good on paper but I've never actually seen it in practice.

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