Hierarchy references

• PMI Work Breakdown Structure practice standard — prior art for deliverable-oriented decomposition and the 100-percent rule.
• Graphviz DOT documentation — supported automatic tree layout.
• Mermaid flowchart syntax — supported hierarchical graph syntax.

Org-chart and taxonomy semantics are conventions rather than one universal interchange standard. Do not claim a generic tree is an ArchiMate or SysML view without implementing that standard.