The pattern languages themselves in this book are static. Organizations are always changing, and the way they change isn't always predictable. Where do the dynamics come from?
The dynamics come in the application of the patterns, and the order in which one applies them. What is the right order, then? One might speculate that one follows the structural relationships between the patterns (as in the sections ProjectManagementPatternLanguage, PiecemealGrowthPatternLanguage, OrganizationalStylePatternLanguage, and PeopleAndCodePatternLanguage, where the relationships are shown graphically). But it doesn't always work that way.
Alexander believes that order in any system fundamentally depends on the process used to build the system. This is why the fundamental process is important (see the section PiecemealGrowth). It is important that each step preserves structure and gradually adds local symmetries, and the organization unfolds over time. It is step-by-step adaptation with feedback. Simply following the pattern language doesn't give you a clue about how to handle the feedback. So that's why the fundamental process exists: to give complete freedom to the design process to attack the weakest part of the system, wherever it may be.
However, the fundamental process cannot work on a human scale without some kind of cognitive guide that is built on experience and which can foresee some of the centers that must be built. That's what patterns are: essential centers.
If unfolding is important, how do you know what order to unfold things? The sequence is crucial. You want a smooth, structure-preserving unfolding. It shouldn't feel like "organizational design."
So, what a sequence does is:
Preserves structure;
Keeps you doing one thing at a time;
Takes the whole organization into account at each step;
May be repeated tens of thousands of times.
Sequences take you into unpredictability, and into circumstances you handle with feedback, always in the context of the whole organization. Sequences are where generativity comes from.
We have created sequences for each pattern language here. Each of these sequences is one of millions of sequences one could hypothesize for each pattern language: there are many meaningful paths through the pattern language graph.
Sequences unfold as stories, and so that's how we present them. These "stories" are sanity checks on the set of patterns they refer to. If these patterns really do belong together, then we should be able to come up with a "story" that flows through the patterns. (And note that this is not necessarily a temporal flow through the patterns.) It may point out patterns that don't quite fit where they are, or don't fit well in the group at all. We might also use the story in the book as an illustration of how the patterns work together. Look at these sequences in the book:
These sequences are real; they come from our experience, and we thought they typified the rich ways in which patterns build on each other, and the way in which the language can become alive.
Of course, each of the CaseStudies could also have a sequence written for it. Each sequence selects patterns which themselves form a small language. That language describes the culture of the organization.