The QuickFix website provides data dictionaries for various versions of FIX (note: I am talking about FIX rather than FIXML). I have not seen any mention of such data dictionaries in the FIX specification, so my assumption is that an independent person (perhaps a QuickFix developer) invented them and they became a de facto standard used across multiple FIX implementations. Does anyone know who invented them? I ask because I want to briefly discuss FIX data dictionaries in a book I am writing, and I would like to credit the inventor.
In addition, I have not been able to find a schema (e.g, DTD or XML Schema) for a FIX data dictionary (again, I am talking about FIX rather than FIXML). Do such things exist?