Hierarchies

A hierarchy of spaces can be generated as there will be spaces within spaces. Hierarchies are created by selecting a space in any arrangement as an envelope and subdivide this space further with selected boundaries. The subdivided space is not changed and 'owns' the spaces resulting from its subdivision. A reference to the space selected as envelope for the new space arrangement is registered using the attribute hierarchy. This registration establishes the hierarchy and allow for querying the original space for sub-arrangements using the backref attribute (that is querying writing q backref on the command line).