Building an Extended Matrix Manually, Unit by Unit

This tutorial walks you through authoring a small EM graph from a written stratigraphic report — no AI extraction, no pre-existing xlsx — so you can feel the formal language with your hands and recognise its parts when they appear in larger projects.

It is the natural follow-up to Creating Your First Extended Matrix: that one shows the mechanics of yEd; this one shows the reasoning.

Learning objectives

By the end you will be able to:

  • read a stratigraphic report and translate it into EM nodes (US, USV, USD, SF) with correct typing;

  • model the most common stratigraphic relationships (stratigraphic_above, contemporary_with, cuts, filled_by) using EM connectors;

  • attach paradata (sources, extractors, properties) to a unit and trace the inference chain back to the source;

  • recognise when a piece of evidence does not fit any node type and decide what to do (discuss, defer, or document the gap).

Prerequisites

Dataset

We use a small, self-contained example: the east cross-section of Trench A at the Casa di Esempio training site. The dataset contains:

  • the report PDF (~3 pages, 8 stratigraphic units, 2 special finds);

  • the section drawing in PNG and SVG;

  • the source PDFs for two of the units.

Todo

Dataset is being prepared. Until then, use any small report with 8–12 units. The instructions below assume 8 US/USD/SF nodes — adapt the count to your material.

The walk-through

We approach each step with the four-column rhythm of Workflows.

Step 1 — Set the canvas and metadata

Data

Panel

Action

Output

your project info

yEd canvas

Drag the EM canvas, fill site code, author, ORCID, licence, embargo.

Empty graph with the metadata frontmatter set.

Step 2 — Catalogue the units before drawing anything

On a sheet of paper (or in a side document), list every stratigraphic unit in the report and decide its type:

  • US — a real, observed body of matter;

  • USD — a documentary unit (something you read about but don’t see physically);

  • USV — a virtual unit, supported by an in-situ anchor;

  • USVn — a typological reference (no anchor on this site);

  • SF / VSF — a special find or a virtual special find.

If you don’t know which one a unit is, write it down — you will ask someone or come back to it.

Step 3 — Place the nodes

Data

Panel

Action

Output

the typed list from Step 2

yEd palette + canvas

Drag one node per unit; set the human ID (e.g. CDE.A.US.001).

One labelled node per unit, no connectors yet.

Step 4 — Draw the relations

Go through the report a second time, this time looking only for verbs of stratigraphic relation: “covers”, “is cut by”, “fills”, “contemporary with”, … For each, pick the matching connector from the EM palette (see EM language docs — Connectors) and draw the arrow.

Step 5 — Attach the sources

For at least two units, drag a Document node, fill its metadata (DOC.001, title, year, page range, file path inside DosCo), and connect it to the unit with the has source connector. We will come back to richer paradata in Linking EM to Your 2D and 3D Documentation.

Step 6 — Save and load in Blender

Data

Panel

Action

Output

the GraphML you just saved

EM Data Tree

Set graph + DosCo paths; Reload.

Your 8 units appear in the Stratigraphy Manager, sources auto-linked.

Self-check

Before moving on, confirm:

  1. Every node has a unique human ID and the right type.

  2. Every relation in the report is represented by exactly one connector — no duplicates, no missing arrows.

  3. The two units with sources show those sources in the Paradata Manager after reload.

  4. Saving and reloading the GraphML produces no validation warnings in the EM Setup panel.

Common pitfalls

  • Mixing USV and USVn: USV must have an in-situ anchor on this site; USVn does not. If in doubt, USVn.

  • Forgetting the canvas metadata: it is the only place where site_code, author and licence live. Without it, every export will be incomplete.

  • Drawing the same relation twice (e.g. a forward and a reverse connector): EM relations are directional and one-way is enough.

Where to go next