Hi! Thanks for the well written document.  Two issues:

# Security considerations

While this document is purely about use cases and does not define a protocol per se, I could see why you might think there are no security considerations. So, two things on this:

1. I tend to think that there is at least one security consideration! Don't you to at least have to at least mention the one issue that affects all of the protocols: time synchronization? If I control your clock, I can make this not work or work at times you didn't want it to.  There has to be some text you can refer to in NTP?

2. I also went and looked at the security considerations sections in other "pure" use case RFCs. YMMV, but many non-security related use case RFCs included text something like:

  This document does not specify a mechanism, it merely motivates TVR.
  Therefore, security considerations are described elsewhere, including
  in TVR requirements [TVR-REQ] as well as in forthcoming documents
  for specific routing protocols.

Totally not wed to the words above and assumes there will be at least one security consideration related to time.

# Possibly an inconsistency.

The last para in s1 includes this text:

  Non-deterministic scenarios such as vehicle-to-vehicle
  communication is out of the scope of the document.

The 1st para of s5.3 includes this text:

  There are a significant number of mobile node use cases, to include
  vehicle-to-vehicle communications, swarms of unmanned aerial and
  underwater vehicles, ships in shipping lanes, airplanes following
  flight plans, and trains and subways.

I was surprised to see “vehicle-to-vehicle” in s5.3 if that’s out of scope.  But, it also made me wonder what is a deterministic scenario and if putting vehicle-to-vehicle in s5.3 make the entire exemplar (and section) out of scope.  Can you explain?