Section: Annex B (informative): Drafting Rules for Information flows
Content: The following drafting rules are recommended for information flows specified in this specification in order to ensure that the Control Plane network functions can be supported with service based interfaces: 1. Information flows should describe the end to end functionality. NF services in clause 5 shall only be derived from the information flows in clause 4. 2. Information flows should strive to use type of interactions such as REQUEST/RESPONSE (e.g. location request, location response), SUBSCRIBE/NOTIFY between Core CP NFs. Any other type of interactions described should have justifications for its use. 3. Information flows should also ensure readability thus the semantics of the REQUEST/RESPONSE should still be maintained (for instance, we need to indicate PDU Session request, PDU Session response and Subscribe for UE location reporting/Notify UE location reporting) for readers and developers to understand the need for a certain transaction. NOTE: As stated in TS 23.501[ System architecture for the 5G System (5GS) ]  [2], service based interface is not supported for N1, N2, N4. Thus, the rules are not meant for those interfaces.