> These days, smart people are advocating the term **short map** for a map \\(F\\) with

>

> \[ d'(F(x),F(x')) \le d(x,x'). \]

This is in line with my intuition - these are exactly "pairwise [Lipschitz continuous](https://en.wikipedia.org/wiki/Lipschitz_continuity) functions with constant 1".

Sorry I screwed up the order previously.

> The concept of \\(\mathcal{V}\\)-functor, introduced above, cleverly slips an inequality into the game. One might have tried demanding

>

> \[ \mathcal{X}(x,x') = \mathcal{X'}(F(x),F(x')) \]

>

> and this would change the answers to "What is a \\(\mathbf{Bool}\\)-functor?" and "What is a \\(\mathbf{Cost}\\)-functor?" in interesting and instructive ways.

To answer "What is a \\(\mathbf{Bool}\\)-functor?", it is an [elementary embedding](https://ncatlab.org/nlab/show/elementary+embedding) of one preorder into another.

To answer "What is a \\(\mathbf{Cost}\\)-functor?", it is a generalization of an [isometry](https://en.wikipedia.org/wiki/Isometry) like you mentioned.

>

> \[ d'(F(x),F(x')) \le d(x,x'). \]

This is in line with my intuition - these are exactly "pairwise [Lipschitz continuous](https://en.wikipedia.org/wiki/Lipschitz_continuity) functions with constant 1".

Sorry I screwed up the order previously.

> The concept of \\(\mathcal{V}\\)-functor, introduced above, cleverly slips an inequality into the game. One might have tried demanding

>

> \[ \mathcal{X}(x,x') = \mathcal{X'}(F(x),F(x')) \]

>

> and this would change the answers to "What is a \\(\mathbf{Bool}\\)-functor?" and "What is a \\(\mathbf{Cost}\\)-functor?" in interesting and instructive ways.

To answer "What is a \\(\mathbf{Bool}\\)-functor?", it is an [elementary embedding](https://ncatlab.org/nlab/show/elementary+embedding) of one preorder into another.

To answer "What is a \\(\mathbf{Cost}\\)-functor?", it is a generalization of an [isometry](https://en.wikipedia.org/wiki/Isometry) like you mentioned.