By "transparency", I'm meaning a system in which the action resolution mechanics (and perhaps also the character build mechanics) are the "physics" of the gameworld - so if you know what's happening in the gameworld you know how to mechanically interpret it, and vice versa. Runequest fits this description, as does Classic Traveller. Rolemaster does at the action resolution stage but not the character build stage. Any more "modern" or "indie" RPG probably does not (eg HeroWars/Quest, The Dying Earth) - in these games the mechanics are often distributing narrative control among players and GM rather than simply modelling the gameworld. 4e is more like this second sort of game than any previous version of D&D.Could you explain what this means, please?
But D&D has always been a bit of a mix between transparency and non-transparency (eg very few people take the hit point rules as a completely literal model with no need for ad hoc narrative glossing) - hence the second part of my post above.