So far as I have - as a complete newbie - understood the data layer by now, it enables the exchange of structured data consisting of various common datatypes between different apps on the ctrlX.
From that point of view it looks a bit like OPC UA and I am wondering, if something like method calls, remote procedure calls, are possible through the data layer.
If not, how does one app make use of the services of another app?
Sorry for the late answer.
Currently it's not possible to call methodes/procedures/ ... at/over the datalayer.
But there are plannings to do this in the future. Concepts already in discussion.