What makes a VW really a VW?

Terra Nova has an excelent blog post, specially because of the comments, on "what should a Virtual World have to become better than WOW and Second Life in a way you would never go back".

Obviously he was not talking about the upcoming "World of Starcraft", and while I don't find them the VW, there are some alternatives coming there that are in all ways better (or so it seems for now) than those two (take Darkfall Battle as an example).

Yet, that post also gave me a new way of looking to VW's by looking into those items that I'm naming as "requisites to make a Virtual World into a really Virtual World". Let me get them for you:

• A World - a defined space which existence is independent of the existence of the players, persistent, and with physics
  
• Players - that operate within the physics, and that represent one virtual individual (avatar)
  
• Interaction between players
• Interaction with the world
• Reaction to the world's changes
• Concept of time, equal to all players and the world
  

And then I had all kind of thoughs on this issues, some of them possibly to be explored in future posts here. You might find these self-evident, but they are not: these, for instance, include talkers as "really VW's" (we should get a name for this), and exclude GuildWars as a VW.