The capabilities fur supporting a built-in datatype should be present in the information model in order to be available in a descriptor. Therefore this is a task for the base facet team to define the necessary UA variables.

I think this is something that just should be described in the Off-line descriptor. In controllers this is usually in a datasheet associate with the product. In a controller the functionblock describe what datatype they use and expose and an empty controller has no functionblocks loaded (FunctionBlock in UAFX is equivalent to FunctionalEntity). A descriptor for a Controller has no FunctionalEntities in it. If you use a different library you will get different datatypes (even an 8 bit processor can have 64 bit integers - they are just implemented in software - same for floating point). This may make sense in a device, but in the device there will be FunctionalEntities.

The idea that a descriptor does not include any information that is not obtained directly from a controller does not make sense. descriptor will have User manual and other external documentation. I would envision that for a controller it will include a description of available functionblocks (libraries). I don't think that this will be generated directly from the controller.

OE team agrees that information on supported data types should be in the (product) descriptor and this information does not need to be present on the online server. But this information needs to be defined in the information model and this needs to be done in part 81 (or in some other base UA spec).

defining it in the information model, mean it is in the server - so the above comment is confusing? OPC UA has aa long list of possible datatype defined in Part 3,5,6 depending on what you are looking for. also other companion specification may further define datatypes.

Part 83 should define a section of the AML file that is to be filled in by the vendor (not generated from a Nodeset) that lists the supported datatypes, a default list could be provided in part 83, but I would just reference part 3/5 for a base list .