Concept-map references

• IHMC CmapTools concept-map overview — prior art for concepts, linking phrases, propositions, hierarchy, and cross-links.
• ISO 704:2022 — terminology principles relevant to concept clarity and definitions.
• Graphviz DOT language — supported graph renderer and layout reference.

There is no universally adopted concept-map interchange standard in diagram.zip. A dedicated concept-map data model and validator would be an integration opportunity.