What this is
In short
A long page is read from top to bottom, and the reader loses the measure of it: how far they have gone, how much is left, and where they stand among its parts. This is what tells them, and what takes them elsewhere in it.
It belongs to no other component. A book uses it, a presentation may, and a page that is simply long uses it as well — the way a sortable table belongs to no bibliography.
Where it comes from
From one requirement of the book: where the reader stands is seen even when the table of contents is not (T9). A table that is set aside shows no entry, and a document read without it leaves the reader with no idea of the way already gone.
The need is not the book's alone, so the answer is not written there.
The requirements
What it has to do
| No. | Requirement |
|---|---|
| P1 | A reader sees how far they have gone in a long page, and how much is left. |
| P2 | The position is seen without being read: no number, no word to decipher. |
| P3 | The position can be told in two ways: the share of the page already gone, or the rank of the part the reader stands in. |
| P4 | The author says what counts as a part, and it is theirs to name: a chapter, a section, or anything they wrote. |
| P5 | When the position is told by parts, their number is seen: a page of forty parts does not look like a page of four. |
| P6 | Showing a place on it takes the reader there. |
| P7 | It follows the reading on its own, and stays true as the reader goes. |
| P8 | What can be done with a mouse can be done without one. |
| P9 | A reader who does not see it is told where they stand, and what moving would do. |
| P10 | A page that does not ask for it carries nothing of it, and pays nothing for it. |
| P11 | On paper it is not printed: a printed page says where it stands by itself. |