The canon, as code

Every rule cites its page.

The books were read cover to cover and encoded as assertions; the test suite reproduces the books' own dimensioned grids: the 8-field, 20-field and 32-field A4 reference grids exactly as printed. When the library and the book disagree, the book is right. A sample of the rules in force:

The rule	Source
No half lines in typography: every vertical distance is whole lines	MB 58–59
Field height is a whole number of text lines; gutters are empty lines	MB 64, 134
The narrower the column, the smaller the typeface	MB 57
Seven to ten words a line; 8–12 pt for the text of books	MB 18, 30–31
Cross‑size register: every style's line height meets one module	MB 59, 66
A picture's width matches the width of a column of text	MB 63
The band under a captioned picture grows in whole body lines	MB 64
Captions belong in the caption column, beside their picture	MB 63, 87, 120
The margin column sits at the outer edge, and mirrors	MB 55
Few graded picture sizes; one picture may dominate	MB 11, 70
The type area floats high: mass may not sink	MB 51
Lines may be set flush right and left, but never the last	MB 80
Statistics have the size of 1, 2, 3 or 4 grid fields, so a chart's bars are whole text lines	MB 14, 58–59
A title is set in its own face, on whole slots of the register; eight canonical placements	MB 46–47, 87
Empty spaces around titles are whole lines; the rest zone gives a title its importance	MB 69–70
A paragraph announces itself by an empty line, an indented first line, or an initial	MB 34, 36
The centred axis is one of the six settings of text	MB 79
A cut-out is tied down by a tint beneath, a field border, bracketing rules, or an overprint	MB 98
The type area may stand in a 1:2 relation to the paper area; wide spines for thick books	MB 51
The mobile grid: one unit count, many simultaneous divisions	Gerstner 58–61
The morphological box: the parameter space, enumerated	Gerstner 59

Sources: Josef Müller-Brockmann, Grid Systems in Graphic Design (Niggli, 1981); Karl Gerstner, Designing Programmes (Niggli, 1964). The books stay out of the repository; buy them, they are worth it. The compiled specification lives in research/foundations.md.