The thesaurus

The thesaurus is the library’s controlled vocabulary: terms arranged from broader to narrower (“Places › France › Paris”), each with its synonyms. It lets you describe the whole corpus with the same words.

Adding a term

New term…, at the top of the screen, opens a sheet: the Label, the Broader term to place it under (Top level, or the selected term, offered by default), then Create.

The Filter terms field narrows the list to the terms whose label or one of whose synonyms contains the text typed.

Editing a term

Choose a term in the list. On the right:

• Label — rename it;
• Broader term — move it under another term, or to the Top level. A term cannot be placed under itself or one of its narrower terms;
• Synonyms — separated by commas.

Then Save (⌘S), at the top of the term’s record; Revert drops the changes.

The rules:

• a label or a synonym belongs to one term only, regardless of case: ““Paris” is already a term or a synonym in the thesaurus”;
• a term always has a label.

Deleting a term

Choose it, then Delete… at the top of its record. Its narrower terms and all their synonyms are deleted with it; the confirmation says how many. Image keywords and tags do not change.

Importing a CSV file

Import… reads a CSV (or TSV; the separator is detected) file with two columns:

• chemin (path) — the terms from broader to narrower, separated by >: Lieux > France > Paris;
• synonymes (synonyms) — separated by |: Lutèce | Ville lumière.

A first header row starting with chemin (or path) is skipped.

Before writing anything, Catalog shows a preview: “Nothing is written yet. Here is what the import would do; an existing term is never moved.” It shows the terms created, the synonyms added, the rows already present and the values set aside, line by line (a line without a term, a synonym that already belongs to another term). Import confirms.

A term in the file that already exists in the thesaurus (by its label or one of its synonyms) is reused where it currently is.

Exporting

Export offers two formats:

• CSV (spreadsheet)… — the chemin and synonymes columns, separated by semicolons, re-importable as is;
• SKOS (RDF/XML)… — the exchange format of collection-management tools: each term is a concept with its preferred label, its alternative labels (the synonyms) and its links to the broader term and the narrower terms.

The thesaurus in the library

• Search — in the library’s search field (and in advanced search, saved searches and the “Relate a file…” picker), a word that is a term or a synonym of the thesaurus also finds the term’s other labels and all its narrower terms. With “Birds” (synonym “Oiseaux”) above “Gull”, birds and oiseaux find the photos tagged “Birds”, “Oiseaux” or “Gull”. Accents and case are ignored; the other words typed still narrow the search (birds sea). A narrower term is searched as a whole word: “Pie” does not find “Pierre”. A very broad term expands to at most 200 labels.
• Keywords — in a photo’s Edit…, Thesaurus: offers the terms that start like the keyword typed; a thesaurus keyword is marked with a book, a free keyword is not, and Add to thesaurus makes it a top-level term (see EXIF and XMP metadata).

Good to know

• The keywords of an imported Lightroom catalog enter the thesaurus with their hierarchy and synonyms (see Import a Lightroom catalog).
• Deleting or renaming a term does not change the keywords already set on photos.