Foreword
I think that the core of every roleplaying is the act of roleplaying itself, wich means that the RPGs are only there to make/do the so-called adventures. Thatswhy I think it is important for us to talk/think about the adventures themselves to understand what is the purpose of an RPG, and after that we should only streamline our RPGs for their purposes.
This is a describing language of adventures wich helps me to think about adventures ad I think it should be thought about adventures. The succession of interactive effects between the players. This version is made for the classical set-up (one almighty GM and more players with one character each).
You don't have to understand anything what I've written before, here you will find no theory at all. You can use this article in its own.
Functions
Functions are the base elements wich make up the planned adventure of a session. The scope of these elements are sized that it is the most useful and confortable for the GM to use them.
There are two main types of functions: mechanical functions and dramatical functions.
Mechanical functions are everything wich is sanctioned by the rules of the RPG. For example most fantasy RPGs have rules for hand-to-hand combat, spell-casting, skill-checks, ability-checks, etc. If the GM will ask the player for a skill check, that's a function. If monsters attack the PCs, that's a function.
The function description of the mechanical functions are mainly references to rules and the needed values. (Only the needed values, nothing else. If monsters attack the party, you won't need their alignment, etc., not even their look, you only need to write down their combat-values.
The dramatical functions are those wich are not based on rules of the game. These can be imagined as the effects you (the GM) want to make on the players (not the characters). For example if the players arrive at a castle, you want to describe the castle. Or if the players meet an NPC or a monster, you want to describe them, too. So, description is a function, too. But the reactions of NPCs are seperate reactions, too. Don't be afraid: you don't need many functions to make up a complex character. Another important type of dramatical functions is the information. The function needs a condition wich has to be achieved and needs an important info wich is given to the players when the conditions are met.
The dramatic functions are described by as few words as it is possible. But they are important, too. They give the structure to the adventure. While the mechanical functions can serve only as the "stuff" of an adventure, dramatical functions have to serve as both the stuff and the frame of the adventure. But function can be a deed that an NPC does without any actions to be reacted.
For example:
- INFO: IF you have the Sacred Sword, the CLERIC tells you about the dragon
- NPC: IF you don't know the sacred rituals, the CLERIC will be angry at you
- NPC: Galdor, the barbarian wants to have a look at the Sacred Sword
etc.
The threads
A thread is a list of functions. You can (and should) make up lists of functions for many reasons. For example an important NPC is a list of reactions.
Deregon, the cleric
- approaches the PCs to tell them about his mysery
- INFO: IF you have the Sacred Sword, the CLERIC tells you about the dragon
- REACT: IF you don't know the sacred rituals, the CLERIC will be angry at you
etc.
There are many other tpyes of threads. For example the begin of an adventure is a railroad of functions. This can be a thread, too, wich are arranged in chronological order. Or if the PCs are trumbling around in a city, the places in the city (the squares, the buildings, the cemetery, etc.) can have all their own threads. The first functions of these threads will be their descriptions, then the next ones will be the conditions wich are needed to enter the building, then the informations wich can be obtained in the buliding, etc. These work like the onion: the first threads are the outer ones, the last ones are the inner ones.
Sessions
The session is the biggest building element of an adventure. You can have plans for long campaigns, but you can really plan only for the next session. You will have many threads, but written dense enough one or two sheets of paper will be enough.
The most important thing: every thread is meant only for the next session. You can have in your mind an NPC with many detailed facets, but you will only need to write down those functions wich will work in the next session. If any detail of the NPC won't show in the next session, it won't show up in the NPC's thread.
I hope this is conclusive enough for you, but any questions are welcome.

concise
a neat way of looking both the story flow and the mechanics of an rpg. i like the idea of preparing the thread of functions, it works well. having the intended play of events in front of your can be very useful and just the process of getting it down on paper concretes it in your mind and helps you sort through any problems.
i have also tried to use flow charts on a larger scale to link smaller events together, it works quite well. simply draw a flow chart of goals and events and how they effect one another. this allows you to prepare for changes in goal, opinion and politics.
to play out smaller events i often sketch up a scene of the room/environment with important objects/people and notes on what might happen, its kind of like a storyboarding of the scene.