I think you explained it better than I did. I never thought of categorizing Check/Carry out/Report and Before/Instead/After as groups like that, but it makes a whole lot of sense.
I always think of the main rulebooks like this:
Before - The player tries an action and you want to check something or alter the game state or try another action first regardless of what happens with the main action.
- Before opening the creaky security door which leads to a room filled with nerve gas, check if the player has a gas mask and have them put it on implicitly before proceeding. The door may be locked, but the player doesn’t know this yet, so putting on the mask can run and succeed or not on its own without interfering with the typed command.
- Before opening the creaky security door, check whether there is a guard is watching the player through the one-way glass. If so, you’re going to send the guard toward the player, but then the door opening action will check and proceed as normal. Whether the player gets the door open or not, that guard is on his way.
Check - The player tries an action. There are many existing checks that Inform takes care of such as Is there enough light? Can the player actually reach this thing? Is the door locked? Any check can fail and stop the action. These are the types of supplementary checks that won’t happen if you used an Instead rule to handle all the different situational elements involved in opening this door.
- Check whether any guard is close enough to the location to interrupt the player opening the door.
Carry Out - All the checks have passed, the action is going to occur. Here is where the world-state changes.
- Carry out opening the door: If the door hasn’t been oiled, send any guard in the vicinity who can hear toward the player.
- Carry out opening the door: If the player didn’t shut off the gas valve, now move the deadly nerve gas backdrop to this room as well.
After - The action has occurred. These rules might trigger a special reaction different from the default report messages. After rules normally stop the action so Report won’t occur unless the author specifies to continue the action.
- After opening the door, if the player hasn’t disabled the security system, sound an alarm and alert all the guards. If one of the guards is close enough, start a fight scene - unless he’s not wearing a gas mask in which case remove the guard and add a corpse to the room. Send all the other guards running for their own gas masks.
- After opening the door: If the player doesn’t have the gas mask on, end the game in death.
Report - Where the normal outcome of the action is communicated to the player. Multiple report rules can fire.
- Report if the door creaks based on whether it’s been oiled or not.
- Report to the player that deadly nerve gas billows out from the next room if they didn’t shut it off earlier and they aren’t dead because they’re wearing the gas mask.
- The standard “You open the security door.” default response will occur whether the special report rules do or not (unless the author overrides it by making one the special report rules stop the action, or by an After rule which prevents Report from running since the fight with the guards or deadly neurotoxin takes precedence over the door opening.)