I overheard someone talking about using the Manhattan metric against nodes on an arbitrary graph (or even a tree). At the time, I didn't think much of it, but having dwelled upon it, does it even make sense?
Clearly, said graph would need to be mapped on to an appropriate space (i.e., $\mathbb{Z}\times\mathbb{Z}$) in a lattice-like fashion. However, wouldn't this preclude the graph from having more than four edges for any particular vertex?
Does it work if you 'latticify' the graph in to $\mathbb{Z}^n$, where $n=\frac{1}{2}\max (\textrm{#edges per vertex})$ -- or something like that -- and likewise extend the metric into $n$-dimensions?