Schematic explanation of aligned rendering of name usages in hierarchies on screen. Name usages in three tree diagrams representing hierarchies, h1, h2 and h3 are aligned with the aid of an aligner tree. Capital letters in hierarchies represent name usages in each hierarchy. The aligner tree is composed from hierarchies as a kind of superset where letters in the aligner tree are place holders to determine vertical offset of nodes. Rendering of a tree diagram in two dimensions based on the folder metaphor requires calculation of node position where horizontal offset depends on depth of the node while vertical offset is relevant to both depth and width. Nodes in hierarchy diagrams can be aligned horizontally by sharing the calculation of vertical offset of nodes. For example, vertical position of node C in hierarchy diagram h1 is determined by vertical offset of node C of the aligner tree while horizontal offset is determined in the diagram h1 alone. Inconsistency between hierarchies results in duplicated nodes in the aligner tree; different assignments of name usage S in hierarchies h2 and h3 results in two S nodes in the aligner tree. Vertical offset of nodes S in hierarchies h2 and h3 are determined by position of corresponding nodes S in the aligner tree. Missing name usages, e.g. name usages B and S in hierarchy h1, result in vacancies in the hierarchy diagrams like vacancy for boundary sets of Rough set representation. Note that such vacancies do not affect the horizontal offset in hierarchy diagrams.

 
  Part of: Ytow N (2016) Taxonaut: an application software for comparative display of multiple taxonomies with a use case of GBIF Species API. Biodiversity Data Journal 4: e9787. https://doi.org/10.3897/BDJ.4.e9787