A target rendered block by block off one value graph, reading @notes, the sum of the terms
added. A change builds only what it changed or newly reads; the rest stays as it stood.
One reading off a buffer nothing rendered — an external file, say — under the profile the
caller names. Every representation needing the graph behind it refuses here.
build’s change, the stream held only while each try runs, between two blocks: an exact
stream pulled once its edit is done plays it where issued. build runs again whenever the
stream changed under it.
What the next second of stream reads off memory, as far as one fetch reaches; a block
reading samples not ready computes them, or, live, starts them silent.
target over tier, from the root down, typed anew only where session typed it
otherwise; a node memory answers stands as its samples. With out dropped and no reading,
a root it answers ends the render unread. Abandoned, it stops before its next block.