The Holographic Principle says that a full description of a volume of space is encoded in the surface that bounds it. This arises from black hole thermodynamics, where the black hole entropy increases with its surface area, not its volume. Everything there is to know about the black hole’s internal content is on its boundary.

Software components have boundaries that are defined by interfaces, which encapsulate everything an outsider needs to know to use it. Everything about its interior is represented by its surface at the boundary. It can be treated like a black box.