Definition: Substrate and schedule

A substrate is $(\Lambda ,d,r)$, where $\Lambda$ is countable, $d$ is integer valued with finite balls, and $r\ge 1$. A schedule $\mathcal{P}=({\mathcal{P}}_s{)}_s$ partitions $\Lambda$ at each tick into finite blocks $b$ with ${\mathrm{diam}}_{d}b\le r$. Tick $s$ maps its input interface to the tick-$(s+1)$ interface.