A ledger is necessary, if only because we are in the space age and there should be computers monitoring almost everything happening in the galaxy.
It would be relatively easy to obfuscate some information that our empire currently doesn't have and to indicate that those information are incomplete (within a range). That way, we could keep the uncertainty about the total strenght of an adversary while being able to guess its force from the troop movements at the frontier and the relevant information that are not blocked (force limit, number of planets). Of course, an espionnage system could likely be built from there and the "ledger" information should be available most of the time in-game.
Let's try something.
Currently, there are two general state in which the relationship between two empires can be : researched and non-researched. We should add some states to that.
- Unknown : of course, no information.
- Explored : You know as much as your ships saw when they visited the zone for the last time. So if you saw them on june 5th 2250, you only see their three corvettes even if they built 10 after that. If you return in their system, the information updates. You don't know if they founded other colonies and have no idea of their technological level.
- Diplomatic contact : At this point, you have a rough idea of their frontiers, but have no idea yet of the strenght of their fleet or the number of spaceports they have. The strenght calculation you may see would be based on how much spaceports they could have, forming the force limit, and then their fleet could be anywhere from zero (or if you see a fleet, that fleet number) to the maximum. Since they sent an embassy to open contact, you can begin to have an idea of their technology at this date.
- Frequent contacts / trade : Since you have access to common knowledge about the empire, you know how many planets and how many spaceports they have. You also know how well those spaceports are upgraded, so you know the empire's force limit. You also still know the fleet number you already saw, so you can guess his fleet number. Technology is, by then, adequately known, meaning you may only lack knowledge of the most recent ones.
- Shared information : If they gave you all their information, you simply have access to everything (number of spaceports, force limit, actual strenght of fleet and technological level until this state ends.
- Closed borders / rivalry / war : At the time one or the other happens, you retain the last information you had about the empire and it no longer updates, since from now on the empire might have taken any decision. The longer this state continues, the fewer the information you have is relevant. You will not know it if one of their spaceport (or their fleet) is destroyed by another empire with which you don't have frequent contacts and you will stop to monitor its technological progress outside of battles. It would be interesting to have the date it happened stored somewhere, because you would behave differently with an empire you cut contacts with 5 years ago than with one you ceased all contacts with 70 years ago.
It ends up looking a lot like currently, but I would like it if a classification like this was adopted, so that we could have limited (or full) information about other empires.
