axis of simmetry
if present, the axis of simmetry is usually taken not only to represent the axis of rotation of the pot, but also often to split the drawing in two parts: on one side, a section is provided, as if the pot was cut along the radius; one the opposite side, a profile from outside is shown. There is no accepted standard of which side should be which.
the Document Object Model is a technical way to describe the “tree” of nested XML tags that compose all documents, including SVG. If a software program is able to manipulate the DOM, this means it could do something useful for you, like filtering out certain parts of the drawing based on attributes.
a drawing is a formal representation of a pot(sherd), intented for the purpose of publishing the exact shape with an optimal use of space on printed paper.