As I continue to read Architecture of the World Wide Web, Volume I, I keep running into material that is completely outside of what I would have expected, yet valuable.
For example, Section 2.2.2 talks about URI allocation. Since URIs are supposed to identify a single resource, it becomes important to make sure that the social organizations which allocate and assign URIs are organized so that they don't allocate the same URI to refer to more than one resource. In other words, we want to make sure that we give organizations authority to assign URIs that don't overlap, so that different organizations don't assign the same URI to different resources (sort of like giving the same Social Security number or driver's license number or bank account number to two different people).
This sort of material may sound obvious when we read it. But it is frequently not obvious to everyone involved in building, deploying, managing, and evolving software systems. In fact, I think failure to make these sorts of issues clear at the architectural and administrative levels is quite possibly the single greatest cause of problems in managing software systems in the real world.