A RESTful Web Services API was added to the product with XPP 9.3.
It is available, and is distributed for use with any new installation or upgrade as of the XPP 9.3 release.
Replace Web Services with a RESTful API that is URL addressable for XPP functionality.
Low-level "micro" services (toxsf, compose, print, citi, etc) supported by XPP, that can be built upon for more high level customized functionality.
The calls can be either. Most of the client functionality (like jquery), can make http get/post calls with callbacks when the data is ready. So it is completely up to the user on how they want to proceed. Of course XPP functionality-wise, you have to create a division, run toxsf, compose, and print in that order to get a PDF from XPP, but that is for the client to handle. For example, with callbacks if you are uploading images, there is no reason to upload one at a time. You can do multiples at the same time and just wait for them to all be completed with a callback.
Bottom line is that if you are calling a URL, it will eventually return something. When and where it is handled is up to the client.