The non-concept vocabulary of the visual layer: diagram types, notations, borrowed field terms and distinctions that deserve a shared definition and a link — but are not ownable coined concepts (those live in the [[mdde-concepts-index|concept library]]).
Terms vs concepts. A term is industry vocabulary we clarify and use consistently — anyone in the field would recognise it. A concept is a named idea this brand coined and owns; you would not find it elsewhere. "Impact analysis" is a term. "Model as Drawing" is a concept.
This is a volatile, promotable layer: a term that keeps recurring, earns its own article, or grows a distinctive angle gets promoted to a concept. Movement in the other direction happens too — a "concept" that turns out to be standard vocabulary belongs here.
Format: Term — one-line definition. → related concept / article.
Diagram types
- ERD (Entity-Relationship Diagram) — Boxes for entities, lines for relationships, marks for cardinality. Exists at three altitudes — conceptual, logical, physical — and mixing them in one picture is the commonest way to lose an audience. → Living Diagrams · Business Friendly Diagramming.
- DAG (Directed Acyclic Graph) — Lineage with execution semantics: the arrows mean runs after, not merely flows into. The acyclic constraint is the useful part — a cycle is a bug the picture exposes.
- Knowledge graph — Entities and their relationships across domains rather than within one schema. Shape is a triple: source · relationship · target — the same shape as a link table, which is why note-vaults and enterprise ontologies converge.
- Context diagram — The fewest boxes, the most deliberation: what this system is and what surrounds it. Almost entirely defined by what you leave out.
- Lineage diagram — Where data comes from and where it goes. Two axes worth navigating separately. → Horizontal Vs Vertical Lineage.
- Impact analysis (a.k.a. reverse lineage, downstream analysis) — Lineage traversed forward: what breaks if I change this? The prospective question that gates action, where lineage answers the retrospective one. → Impact Analysis.
Notations & formats
- Mermaid — Text-based diagram DSL that renders inline in Markdown, GitHub and Obsidian. The pragmatic default when the diagram belongs beside the code.
- GraphML — XML graph interchange format; yEd's native input. Where auto-layout earns its keep on graphs nobody can hand-arrange.
- mxGraph /
.drawio — draw.io's XML format. Also the basis of mxlibrary, the shape-library format behind Generated Palettes.
- JSON Canvas — Open spec (1.0) for infinite canvases:
nodes + edges, with file nodes referencing real notes. Published by Obsidian, implementable by anyone.
- Excalidraw — JSON format for hand-drawn-style diagrams. The sketchy look is a feature: it reads as provisional and invites correction.
- ArchiMate — Enterprise-architecture modelling language; Archi is the common open tool. → MDDE ADR-86.
- PlantUML / Graphviz — Text-to-diagram tools whose value is the layout engine: you say what connects, they decide where it goes.
Techniques
- Round-trip — Generating into a format and parsing back out of it, so an edited drawing returns to the model instead of stranding. The difference between a canvas as input and a canvas as dead end.
- Drill-down — Opening a collapsed node in place rather than navigating to another artifact. What makes aggregation honest instead of merely hiding.
- Aggregation (roll-up) — Collapsing a set of nodes into one until the reader asks for detail. The move that makes large graphs legible without deleting anything.
- Blast radius — The bounded set of things affected by a change. Impact analysis without a depth limit returns the whole platform and answers nothing.
- Layout engine — The algorithm that decides where nodes go. Solves arrangement, never scope — a well-routed hairball is still a hairball.
- Scene-embedded export — PNG/SVG carrying its own source data, so the exported image remains editable. One asset that is also the source.
Borrowed from the field
- Visual facilitation — Guiding a group to a shared picture of a contested idea (sketchnoting, graphic recording). A neighbouring profession, not ours. → Drawing It Together.
- Book-on-a-page — Compressing an entire book into one visual summary. A modelling exercise in disguise: it forces the question what actually matters here?
- Sketchnoting — Visual note-taking during listening. The evidence that drawing is cognition rather than decoration.
- Bus factor — How many people must disappear before something becomes unmaintainable. → Bus Factor of One (SBM concept library).
Promotion candidates
Terms recurring often enough to be worth watching:
| Term | Why it might become a concept |
|---|
| Blast radius | Already doing conceptual work in the impact-analysis argument |
| Round-trip | Central to the thesis; may deserve its own name |
| Drill-down | Currently generic; the generated version has a distinctive angle |