Alternating repetition is the second of three consecutive properties in The Nature of Order which make little sense if you apply them directly to software. It is curious that Christopher Alexander arranged them consecutively, because, as I have mentioned in the previous chapter, Boundaries, this and the following chapter (Positive Space) share a sort of meta-characteristic, which can be pronounced like “the space between the centers is itself a center”.
Given this state of affairs, I am going to use this space to talk more about this meta-property, and how it is inflected by the original geometric property from the book. This is of course after I tell you what it means for buildings.
Buildings tend to have, for instance, structural elements that repeat. Whether they are piers, or bays, or vaults, or columns, or joists, or rafters (they don’t have to be load-bearing either, they could be dormers or even ornaments), buildings are full of features that are usually evenly-spaced, identical copies of an elementary structure. Alexander argues that the space is more whole when the gaps between these features are discernible features in themselves.