when a station is older than a program it is affiliated too (date established < begin date of program) which one of those should we use as the begin date for program/network affiliation?
I would argue that you should use the date of establishment of the program in that case.
The use case is not clear, unfortunately:
UC1: Programs come with specific requirements, and if a station/platform has fulfilled these requirements even before a program officially existed, the date to choose could be that earlier date.
UC2: If a statistic should be established on the number of stations/platforms that belong to a specific network/program in each given year, then it makes sense to assign the date when a station/platform joined that program - so the earliest date would be the date when the program was established. I think, this is the more relevant UC.
Hope this helps.
As I already had some problems/questions (on meeting) regarding the "network affiliation" (also some of NFP from my region) , and this answer to Sike just confirm my dilema, I would like to ask for a more detailed explanation of this term.
Just to mentioned that I claimed (on TT-OD meeting in Geneva) that, my understanding of a term "network affiliation" is that not all stations which do the e.g. climat observation are affiliate with GCOS program, but only those which are choosen by GCOS . For example, there are 14 stations which are doing climatological measurements in BiH but only station Bjelasnica is affiliate to GCOS.
Do I misunderstand word "affiliate" ???
your understanding is correct, a program/network affiliation means a formal acceptance of a given station/platform/facility by a program/network. The governance of programs/networks can be different for different programs/networks. In the case of GCOS, GAW, GRUAN and a few others, a facility may apply to become affiliated, but the program/network manager will approve or disapprove this. On the other hand, for GOS, there is no such approval at present.
The work-flows in OSCAR/Surface are modeled accordingly: If a stations requests to be affiliated with GCOS by linking an observation to GCOS, the responsible program manager at WMO will be informed and needs to approve this affiliation, otherwise it will not be visible for the public.
Hope this helps.