The external object may be any object that can exist within the system. The document holds the root of the tree of units, a link with the TEXT instance managing the text of the document, and tables for recording the names of units in the document tree, names of external objects, and status names. External objects cannot be part of any document tree. Status names are associated with the values 'include', 'ignore' or 'temp'. The links with a text instance and the root of the document tree are immutable.
Text Documents implement a view on a sequence of data characters, called the text .
The text is managed by a TEXT instance. This instance renders services for accessing and updating the text. The text instance communicates with units by pseudo-data objects, strings and patterns passed forth and back. The complete text managed by the text instance is covered completely by the document element. All child units in sequence cover all text covered by the parent unit.