
Dynamic and Sustainable are the two key objectives of good Storyworld design. Not every story idea will make for a good Storyworld. Not every plot can move across platforms. A good Storyworld will have its own internal combustion that spawns complex dynamics and frictions and will do so in a way that is sustainable over time.
A Storyworld lives and dies by it’s dramatic sustainability and if you focus on plot before fully considering the rules, contexts and natural pressures of your story-world, you run the risk of writing your world into an unsustainable hole. A good Storyworld will be self perpetuating by its own natural dramatic momentum. .
But how do you write a Storyworld without writing Plot? One of the most important steps to building internal combustion and sustainability for a multitude of plots is the articulation of the Storyworld Timeline.
Seminal film scholar David Bordwell defines narrative cinema as 'a series of events in a cause and effect chain within time and space'. It’s a remarkably succinct and powerful definition which allows us to see Story as predicated on Causality - cause and effect - where an event triggers an action which leads to new events which cause new actions and so on. Catherine Millar, head of screen content at the Australian Film TV and Radio School describes this in wonderfully simple terms as the “BUT, SO” process. Think of it like this - once there was X who was Y, BUT then Z happened. SO X had to do A. BUT then B happened and SO X and to discover C in order to D. BUT then…. so on and so on, you get the picture. This is a 'causal-chain' and its the fundamental base element of storytelling.
However, conceiving of your Storyworld as simply a series of events is a rather simplistic approach. What we need to do is interrogate the causal chain of the timeline to understand the different pressures and influences those events represent; which really is to understand the impact the timeline events have on the Storyworld - how it has been shaped by them.
In this regard we might consider Storyworld Timeline events as tending to fall into three main categories:
INFLUENCING EVENTS - Events that happen that alter behavior from that point or which shape, redefine or alter a character, entity or institution driving it toward the current state of being.
DECISIONS - specific choices taken by a character, society, organization or entity which represent a fork in the road. Points on the timeline where a decision was made that altered the trajectory of the ‘Storyworld’.
MILSTONES - a moment or event in the timeline where a threshold is passed and from which there is no turning back for a character, institution or society. A timeline Milestone is a saturation point, a moment of critical mass and transformation.
By this triumvirate we have a process of Storyworld construction where we can see Influencing Events and Decisions as being dramatic triggers that lead to Milestones, thresholds of no return in the Storyworld. And it is the constructing of Milestone thresholds that are the foundation of your Storyworld - the rules in which it will function.
By way of example we can look to the rather definitive Storyworld of the Harry Potter series. The example below is a timeline of major events in the Harry Potter world. Importantly the timeline sets out events that precede the launch point of the story as contained in the books and provide the background context for that plot as a section of the bigger timeline.

timeline of Harry Potter Series
Looking at the events on the timeline we can see that they tend to fall into the three categories detailed above.
Influencing Events, those things that prompt change or impact upon the characters and institutions down the line, can be seen in such points as the TriWizard Tournament and Dumbledore becoming headmaster Hogwarts. These are simple events may seem mundane at the time that have profound importance and impact down the timeline.
Similarly there are Choices inherent in the Harry Potter Storyworld timeline; those specific decisions taken at a fork in the road. We see this in Tom Riddle opening the chamber of secrets and later the choice by Hogwarts to reject Voldermort for a teaching position. The importance of choices is that if a different choice been made the Storyworld would be entirely different. eg, if Voldermort had been given the teaching position he may never have turned into such a nasty bastard.
Finally the timeline encapsulates clear Milestones; Tom Riddle becoming Voldermort being the most obvious. This milestone of transformation clearly represents the point of no return, not just for the character of Tom Riddle but for the Harry Potter Storyworld as we know it.
The key point to this idea of conceptualizing your Storyworld timeline events as straddling these three types is to ensure that the Storyworld has natural dynamism and energy. If your timeline, for example, is populated entirely with Influencing Events but is lacking in Decisions than this may indicate that your Influencing Events are not compelling or high-stakes enough as they haven’t forced characters or institutions to make decisions. Likewise if you are lacking Milestones - timeline events where there is a point of no return - then you may have neglected to provide your characters and institutions with thresholds to pass. Such stories will likely be lacking crises, climaxes and natural peaks of drama to be built towards. The result being a Storyworld that is dramatically flat, lacking tension and release.
In this way the constructing of a timeline not only serves as a powerful tool for conceiving a Storyworld but also a way to test your Storyworld, to measure its robustness and dynamics to ensure it is dramatically sustainable.