Rest API schema files files do not validate and present errors if edited with tools such as MS Visual Studio or Altova XML Spy.

The issue can be verified with Netbeans as well.

steps to reproduce (in netbeans)

• select all xsd files in vendor/ezsystems/ezpublish-kernel/doc/specifications/rest/xsd/
• right click on the list of files and select Validate XML
  => Errors such as the following will be showed

  Referenced entity at "nbres:/org/netbeans/modules/xml/catalog/resources/datatypes.dtd".
  cvc-complex-type.2.4.a: Invalid content was found starting with element 'xsd:all'. One of '{"http://www.w3.org/2001/XMLSchema":annotation, "http://www.w3.org/2001/XMLSchema":restriction, "http://www.w3.org/2001/XMLSchema":extension}' is expected. [6]