Object tree

From IFWiki

An abstract programming structure denoting the containment of objects. This is generally used in manipulation of objects (as Inform and Hugo do with "move chalk to player" and "remove hat") and in listing a room's contents, especially if a certain order is necessary. An object tree is generally described in programming in terms of "parentage." For example, if the player is holding a piece of chalk, the player is considered the "parent" of the chalk since the chalk object is contained in the player object.