There are three answers to this very frequently asked question. First of all, if you decide to use RESTful HTTP together with XML — a very common choice — the whole world of XML schema languages, such as DTDs, XML Schema, RELAX NG or Schematron are still available to you. Arguably, 95% of what you usually describe using WSDL is not tied to WSDL at all, but rather concerned with the XML Schema comp