glossary
Hierarchy
Hierarchy is a tree of named drawings in which a large drawing is built from stamps of smaller named drawings.
A modern chip is too large to keep as one flat pile of rectangles. The tree keeps the file smaller, keeps an edit in one place, and matches the way the work is divided: pad, standard cell, block, chip. It also hides mistakes. A bad via drawn in a master appears in every stamp of that master, and a good via does too. A tree view might list chip at the top, then core, then sram_bank, then bit. Expand bit and the leaves are shapes. A million bits can be four cells plus a large number of instance records.
The outer frame holds two different named drawings: a crossing with a plug, and a landing.
A regular grid of the same stamp is an array. Turning the whole tree into one cell full of raw shapes is to flatten it. Board tools often live flatter, because a footprint is placed once and rarely nests ten levels deep. The tree is also an agreement about ownership: who owns the bit cell, who owns the bank, and who is allowed to flatten the design for tapeout.