I love this topic. I completely understand the irritation that incursions cause and of course the game can be designed to limit this if they choose to do so. There are plenty of games that stop you at borders.

Personally, I stand on the no borders side. I really liked Erischild's ocean analogy. Think of land masses as space colonies. Areas of influence or hegemony might extend far into the ocean that surrounds them. Nothing but a puny 2-3 mile limit is considered an incursion. Even that limit is frequently violated by fishermen from other nations. Violations do occasionally result in real world diplomatic penalties but I am not aware of any war started by a coastline violation unless it was an obvious invasion fleet. Thousands of ships move at will in the waters that surround land masses.

We currently have no laws related to space and there is no doubt in my mind that when we start populating the solar system it will be a free for all. Even the planets themselves are in question. We planted a flag on the Moon nearly 50 years ago. The Chinese are likely to plant another one in the next decade. Shall we declare war on the Chinese? Suppose we establish a permanent base on the Moon, as it is currently planned, I believe. Does that give us a valid claim to the entire surface of the Moon? What about Mars? We have spent billions exploring and mapping the surface of Mars and we are likely to establish a colony there in the next century. Will the first settlers claim ownership of Mars, and resist any efforts by others to colonize the other side of the planet? The issues that we will face are extremely complex and they are fraught with danger. Future land issues on planets, moons and asteroids could easily erupt into wars there and on Earth, assuming we are still a world of national boundaries. 

The issues of the OP are less complex to me. If the AI incurs you can ignore it and their colony will soon be overtaken by your influence. If you consider it a Casus Belli, wipe them out and take the diplomatic penalty that goes with it. I do wish they would nerf the diplomatic penalty between friends and allies. Who cares if your enemies hate you a little more. I also wish that star bases would be subject to influence and flip to you. I am almost certain that they did so in GCII, unless I dreamed it.

Maybe it is just my style of play but I have had no major problems with this issue. I will usually wind up with open border treaties with any friendly faction and occasionally with less than friendly, if I feel it is to my advantage. Open borders improve your diplomatic status dramatically and does not seem to cause any great increase in incursions on big maps. The Drengi likes to tell me every 3-4 turns how much the open borders treaty has improved our relationship. The others do the same thing of course but only the Drengi amuse me with their friendly communications.  

On any map, if you sit around and leave assets untouched in your empire, they will eventually come for them. The answer is simply, you get there first.     

To those who claim there can't be borders in space...you do realize this is not the main point right? The point is that if another faction does something that is blatantly against your own best interests such as colonizing a planet in a system that already has another planet you own, then it makes sense that the player would see this as an aggressive act and respond accordingly. Nations defend their own interest. It doesn't make sense that a faction can do something that massively goes against your own interest and yet people still treat you like a bad guy if you respond.

Your idea doesn't make sense. The problem with your premise is that you assume that this is merely a matter of culture. It isn't. Do you think humans are aggressive just because they feel like being so? The reason for why empires go to war over territory is because of economic competition. A piece of land containing important resources, as well as living space for future generations, can't be secured if somebody else takes it first. That is why nations and empires don't kind it kindly when somebody starts expanding into their territory. If a civilization is able to make it into space then they are industrialized and thus need resources and land just like everybody else.

And thus, your argument fails.

don't know about territorial good points either way. I wouldn't mind real boundaries in space more smaller than influence borders of course maybe a up resolution. Here's one thing to remember you will probably want to make it only after the colony rush, or you will be smaller than planned with a bunch of independent planets. Same rule as before no closed borders. If you want it this way defend your own space.

@hardcore gamer

I think humans are the way they are because of our particular evolutionary history. I highly doubt an intelligent species evolved from say... nomadic herd animals, will have the same natural conception of territory and what is "yours" versus "mine" that we do. You even get these different views within the same species depending on their mode of existence, the dichotomy and misunderstandings of the Spanish meeting the Native Americans the first time they met (the Spanish thought "gifts" were permanent property, the Native Americans, less so).

Now, would I, if I were running a civilization, naturally want to accumulate resources and defend territory? Sure... but I am, inescapably, human, and those other races are not, they are not beholden to what I think is reasonable. 

Also bear in mind, that I am one of the few people who've posted thus far supporting Real borders, for the most part, I think empires would try to "boguard" their backyard planets, I just think the game will be more creative if some of the AI's happen to be jerks and not care, and real borders should definitely not be as expansive as influence typically is, as that covers vast swaths of empty space.

PS: The fact that this issue about real borders is contentious amongst forum posters, (who are presumably all of the same species and mostly of the same overall cultural foundations) is more than enough proof that wildly different alien species will also consider real borders that cover star systems you barely colonize as contentious as well.

I suggest we just focus on what is "fun" and what is not "fun". You clearly just don't LIKE that the AI does this, and it is a stupid waste of resources in most situations, so the AI should be made smarter about how to deal with it, at the least.

actually a tactic I never thought of. As far as real borders their needs to be an exemption for species totally surrounded by other species borders.

The fact of the matter is, if the AI colonizes a planet in your influence then that's basically a free planet for you within the next 20-odd turns. If not, then you weren't that powerful there anyway and have no grounds to declare it yours.

But we need to abandon this silly open vs closed borders argument, because it's a distraction from the real issue. The real issue is that the AI doesn't really understand or care about influence. It doesn't get the fact that planets within my influence will pretty much belong to me whether I colonize them or just cultural flip them later; it needs to push the border back before anything more than 5-6 hexes into my space is a legitimate target. This applies to invasions, too - far too often I've watched the AI (once it's had it's arbitrarily short transport targeting range removed) take an individual planet in a cluster of 4-5 and not send any further support until long after it's flipped back. The really annoying problem with the AI dropping colonies into my back field has nothing much to do with it damaging me, since ultimately it doesn't; it's just bloody irritating.

Influence, as we're so often told, isn't a border. I'm ok with that. However, it IS a sphere of influence - which, in the parlance of the Great Powers, essentially refers to the area outside their direct control where outside interference will none the less provoke a hostile reaction. The AI needs to understand that that's exactly how most players will view it, too, and so shouldn't attempt to violate influence unless it brings enough force to literally take the area from my influence and adding it to it's own.

I actually suspect that players would be less annoyed by it if this were the case - if the AI suddenly settled 4-5 planets close together and within your influence, and so flipped the region to itself, then that should be applauded as good, challenging AI play. It would be a rare, daring move. But instead, we have - in literally every game - the throwing colony ships at junk class-5 worlds that will inevitably flip to me before they've built 3 buildings. That's boring, predictable, irritating, a waste of resources and ultimately a matter of the AI doing something bloody stupid, rather than an intended strategy.

Communist Russia never got rid of the idea of ownership. Even in the soviet union everything was state-owned.

Well I said "evolved from nomadic..." not "IS CURRENTLY NOMADIC". They may well develop sedentary settlements ala humanity, but it wasn't a product of their nature, and would result in a different mindset.

I'm not even touching the whole socialist/ownership thing lol... 

At any rate. Naselus was quite on point with his post. The AI is the issue, and it doesn't understand influence. Not a complete solution, but I've long felt that a easy way to help balance culture flipping would be for the planet, not to go into your control, but rather, to become completely independent first.

You thus deprive the enemy of his planet's use, but you don't instantly get the planet for yourself, there is no sudden reversal of power. You could have the planet eventually, fully flip, but this could be very long term, and it may well be more useful to just invade it (it would suffer a penalty to defense since they believe in your culture anyways).

I suspect the problem comes back to an inability to code the AI to respect such a border. As allready noted Influence allready IS borders because the AI gets pissy about you going inside their borders with anything pretty hard. So from an AI diplomacy PoV Influence = Borders. It's just that the AI willfully ignores that with each other and the player.