Etymology

[Fred76]

Even if we know the arbitrary part of the choice of a puzzle name, I think a good definition should take into consideration the etymology of the puzzle name. For example, I would never say about a hexagonal grid that it is a "latin square", it would be contradictory (I don't think latin squares can have geometrical variations).

For sudoku:

from Japanese sūdoku, from sū(ji) ‘number’ + doku(shin) ‘single status’ after sūji wa dokushin ni kagiru, literally ‘the numbers are restricted to single status’

In this respect, I think that it's hard to label puzzles with repetition of symbols/digits as "sudoku".

Fred

[detuned]

A hexagonal grid can be equivalent to a square grid with diagonal constraints - I suppose it depends on how you think about these things

[detuned]

I should add I'm halfway through writing the report - I might add the point about etymology to it, but it will certainly not be the defining feature of it, for a number of reasons (including the one above).

To shed a little more light on how things are shaping up, I think everything in this forum so far can be condensed to defining what a classic sudoku "looks like" and how it "solves like".