[DurNominator]

My listing for RPI feature set would be features that help in making the roleplaying atmosphere more intense. Here are few features I'd expect a true RPI to have. Personally, I wouldn't use some "historical three" as a guideline, as games evolve and implement better features. Thus, I'd like to propose a following development goals for any game (I would not restrict RPI concept for MUD use, as one can say RPI MUD to specify) that wants to call itself RPI:

-One important factor is realistic-based character advancement, which means that the most effective way of character advancement would be similar to the way it is done in real life. Thus, you'd only learn so much coding from typing Treshold's code snippet over and over. The skill based/level based discussion is sort of moot, as the advancement is measured with integers in both cases. Thus, the important part is the realisticness of the advancement, not complete hiding the code or levels, as the player behaviour will be the same if the game is properly coded. Only reason to hide the system is players min-maxing the system due to the inferior nature of the system design in RPI-sense. Thus, the hiding of code itself shouldn't be a requirement, but can be used as a trick to make it easier to build an RPI, as it protects your inferior code from being discovered.

-Realistic game physics. This means that your actions have consequences, whatever is appropriate in that particular world, such as jumping off a cliff would cause you to fall down if a force pulling you downwards, such as gravity, is present in the enviroment and you do not have means to counter it. Ideally, people wouldn't be able to do what is not possible in their world. Permadeath is not a requirement per se, but there should be a convincing explanation why the resurrection is possible RP-wise.

-Realistic game culture. Actions should also have realistic social consequences. For example, if you clear out an area hack&slash style, the heinous mass murder should have some consequences, such as the town you committed your crime in turning hostile towards you, providing that the deed does not go unnoticed. Anyway, the world would be affected by the actions of players and thus, working as a deterrent for heinous deeds if the players do not wish to face the consequences. Thus, hack & slashing creatures wouldn't be against the rules per se, but the adverse effects would automatically create an enviroment where it is a rare deed.

-Intuitive user interface. The game system should be simple enough to use so that the mechanics do not become a hindrance to roleplay.