Documenting fundamental concepts

The specification alludes to various concepts that aren't described in detail when they are mentioned. Organisationally this makes sense, to ensure the specification is tractable for implementation. However, understanding those concepts is essential for implementers and we would do well to have a canonical set of references to describe those concepts (i.e. delegation graphs, terminating flag, hashed bins and possibly more in the current spec and while adding TAP 4, with more coming down the pike in Draft TAPs).

Currently consistent snapshots has its own section in the spec, whilst other concepts are only lightly covered or not covered.

We could take one of the following approaches to better document these conceptual issues:

• TAPs: where the concept is already well described by the TAP that introduced it, link to that TAP. Otherwise create an informational TAP to describe the concept and link to that.
• Concept section/appendix in the specification: akin to the existing content on consistent snapshots.
• Combination: light summary in the specification and link to supplementary material (TAPs, papers) for more detail.

Start by reading the specification's existing consistent snapshots section and the TAP 4 document linked in the issue. Catalog concepts such as delegation graphs, the terminating flag, and hashed bins, then determine which references or summaries are missing. Done means the specification has a consistent canonical reference approach for these concepts and links or explanatory material for the identified gaps.