So, with the upcoming sov changes due to release this summer there will be a lot of people looking to own a bit of space in null-sec. Whether they will be successful or not remains to be seen. This and a conversation I had got me thinking about what "owning" space means.
I'll warn you that I haven't figured it all out and the following is just the start of my thoughts.
In EvE you can mechanically own a system by claiming sov. However, that does not mean you really own it. You could be there only by the grace of some greater power whether by renting it or simply because they want you as a buffer or as content for their members.
On the other hand, you CAN own space even where there is no mechanical way to do so. Wormhole groups certainly don't let a lack of sov mechanic stop them from claiming wormholes as their own. Low sec groups and NPC null groups can dominate large portions of space even though they nominally under the control of NPC factions.
I would say ownership of space comes down to being able to use the space as you see fit AND having the power to protect that ability. Other people may live there but it is by your grace and they could be ejected if that is what you desire. This could take many forms. It could be the industrial alliance that wants to build and mine. It could be the safe haven for a pirate corp to rat and run sites to fund their PvP habit. It could be building a mighty POCO empire for passive income.
I will also point out that not everyone wants to own space and it isn't necessary to really do much of anything in the game. You can raid other people's space for minerals or sites. Or raid it for content by getting fights from them. You can do this as a nomad or being settled in an NPC station. You could have the ability to control the space but would rather just let people come and go as they please.
So, in the end, I think that "owning" space might be as much of a mindset as it is anything you can do in game.