XML (and those prolog and KDL expressions) have one big advantage over JSON: The type (in XML the tag name) comes before the rest of the object. In JSON it's us

XML (and those prolog and KDL expressions) have one big advantage over JSON: The type (in XML the tag name) comes before the rest of the object. In JSON it's usually a type field. That means in JSON it could come at any point and thus you have to load the whole sub-structure as a dynamic hash map before you can evaluate the type field and instantiate the correct type in your programming language. With XML using a SaX parser you are guaranteed to get the type first and thus can immediately instantiate the correct type and load the properties into that, skipping any dynamic hash map. Depending on your application this can mean a big performance difference.