eccenca · seebi · Sep 5, 2026 · Sep 5, 2026 · Sep 5, 2026
diff --git a/.github/ISSUE_TEMPLATE/bug.yml b/.github/ISSUE_TEMPLATE/bug.yml
@@ -9,6 +9,7 @@ body:
       label: Contribution guidelines
       description: Please read the contribution guidelines before proceeding.
       options:
+        # yamllint disable-line rule:line-length
         - label: I've read the [contribution guidelines](https://github.com/eccenca/documentation.eccenca.com/blob/main/CONTRIBUTING.md) and wholeheartedly agree.
           required: true
   - type: textarea

diff --git a/.gitpod.yml b/.gitpod.yml
@@ -1,3 +1,4 @@
+---
 ports:
   - port: 8000
 tasks:
@@ -13,7 +14,7 @@ github:
     # enable for the default branch (defaults to true)
     main: true
     # enable for all branches in this repo (defaults to false)
-    branches: true # change it to false
+    branches: true  # change it to false
     # enable for pull requests coming from this repo (defaults to true)
     pullRequests: true
     # enable for pull requests coming from forks (defaults to false)

diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
@@ -1,4 +1,3 @@
-
 ---
 repos:
   - repo: local
@@ -10,6 +9,13 @@ repos:
         language: python
         pass_filenames: false
 
+      - id: yamllint
+        name: check:yamllint
+        entry: task check:yamllint
+        language: python
+        pass_filenames: false
+        files: '\.(yml|yaml)$|(^|/)\.pages$|^\.yamllint$'
+
       - id: nav-drift
         name: check:navigation
         entry: task check:navigation

diff --git a/.yamllint b/.yamllint
@@ -0,0 +1,26 @@
+---
+# Mirrors ~/.config/yamllint/config so `task check:yamllint` behaves identically
+# for a local run and on CI, where no user-level yamllint config exists and the
+# stricter upstream defaults (notably line-length 80) would otherwise apply.
+extends: default
+
+# The navigation source files are YAML but carry no extension yamllint knows
+# about, so they have to be named explicitly alongside the built-in globs.
+yaml-files:
+    - '*.yaml'
+    - '*.yml'
+    - '.yamllint'
+    - '.pages'
+
+rules:
+    empty-lines:
+        max-end: 1  # allow for one empty line at the end
+    line-length:
+        max: 120
+    # `on:` in a GitHub workflow is a mapping key, not the boolean `on`
+    truthy:
+        check-keys: false
+
+ignore: |
+    /site/
+    /.venv/
diff --git a/README.md b/README.md
@@ -86,6 +86,11 @@ fail the build.
 `task check:navigation` additionally fails if `nav.yml` no longer matches the `docs/**/.pages`
 files, which remain the source of truth for navigation (`task update:navigation` regenerates it).
 
+`task check:yamllint` lints every YAML file in the repository, including the extensionless
+`.pages` navigation sources, against the committed `.yamllint`. That config is committed rather
+than left to a user-level one so a local run and a CI run apply the same rules - without it CI
+would fall back to yamllint's stricter upstream defaults.
+
 See `tasks/handoff.md` for the full migration notes.
 
 ## License

diff --git a/Taskfile.yml b/Taskfile.yml
@@ -59,7 +59,7 @@ tasks:
       - poetry install
 
   check:
-    desc: Check documentation links, Markdown style, nav drift and build output
+    desc: Check documentation links, Markdown and YAML style, nav drift and build output
     # Sequential (`cmds`, not `deps`) on purpose. Task resolves `deps` in
     # parallel, which ran several `poetry install` invocations at once and, worse,
     # ran `zensical build` alongside the link and style checks - under that load
@@ -69,9 +69,19 @@ tasks:
     cmds:
       - task: check:links
       - task: check:rumdl
+      - task: check:yamllint
       - task: check:navigation
       - task: check:output
 
+  check:yamllint:
+    desc: Fail if any YAML file deviates from the style in .yamllint
+    deps:
+      - install
+    cmds:
+      # `.` picks up the repo .yamllint, which is what makes a local run and a
+      # CI run agree: GitHub runners have no user-level yamllint config.
+      - poetry run yamllint .
+
   check:navigation:
     desc: Fail if nav.yml is out of sync with the docs/**/.pages files
     deps:

diff --git a/docs/.pages b/docs/.pages
@@ -1,3 +1,4 @@
+---
 nav:
     - Build: build
     - Explore: explore-and-author

diff --git a/docs/automate/.pages b/docs/automate/.pages
@@ -1,3 +1,4 @@
+---
 nav:
     - Automate: index.md
     - cmemc: cmemc-command-line-interface

diff --git a/docs/automate/cmemc-command-line-interface/.pages b/docs/automate/cmemc-command-line-interface/.pages
@@ -1,3 +1,4 @@
+---
 nav:
     - cmemc - Command Line Interface: index.md
     - Installation: installation

diff --git a/docs/automate/cmemc-command-line-interface/configuration/.pages b/docs/automate/cmemc-command-line-interface/configuration/.pages
@@ -1,3 +1,4 @@
+---
 nav:
     - Configuration: index.md
     - File-based: file-based-configuration

diff --git a/docs/automate/cmemc-command-line-interface/invocation/.pages b/docs/automate/cmemc-command-line-interface/invocation/.pages
@@ -1,3 +1,4 @@
+---
 nav:
     - Invocation: index.md
     - Docker Image: docker-image

diff --git a/docs/build/.pages b/docs/build/.pages
@@ -1,3 +1,4 @@
+---
 nav:
     - Build: index.md
     - Introduction to the User Interface: introduction-to-the-user-interface

diff --git a/docs/build/reference/.pages b/docs/build/reference/.pages
@@ -1,7 +1,8 @@
+---
 nav:
     - "Task and Operator Reference": index.md
     - "Aggregators": aggregator
     - "Custom Workflow Tasks": customtask
     - "Datasets": dataset
     - "Distance Measures": distancemeasure
-    - "Transformers": transformer
+    - "Transformers": transformer
diff --git a/docs/build/reference/aggregator/.pages b/docs/build/reference/aggregator/.pages
@@ -1,3 +1,4 @@
+---
 nav:
     - index.md
     - "And": min.md
@@ -8,4 +9,4 @@ nav:
     - "Handle missing values": handleMissingValues.md
     - "Negate": negate.md
     - "Or": max.md
-    - "Scale": scale.md
+    - "Scale": scale.md
diff --git a/docs/build/reference/customtask/.pages b/docs/build/reference/customtask/.pages
@@ -1,3 +1,4 @@
+---
 nav:
     - index.md
     - "Add project files": addProjectFiles.md
@@ -88,4 +89,4 @@ nav:
     - "Validate Knowledge Graph": cmem_plugin_validation-validate-ValidateGraph.md
     - "Validate OWL consistency": cmem_plugin_reason-plugin_validate-ValidatePlugin.md
     - "Validate XML": validateXsdOperator.md
-    - "XSLT": xsltOperator.md
+    - "XSLT": xsltOperator.md
diff --git a/docs/build/reference/dataset/.pages b/docs/build/reference/dataset/.pages
@@ -1,3 +1,4 @@
+---
 nav:
     - index.md
     - "Alignment": alignment.md
@@ -24,4 +25,4 @@ nav:
     - "Snowflake SQL endpoint": SnowflakeJdbc.md
     - "SPARQL endpoint": sparqlEndpoint.md
     - "Text": text.md
-    - "XML": xml.md
+    - "XML": xml.md
diff --git a/docs/build/reference/distancemeasure/.pages b/docs/build/reference/distancemeasure/.pages
@@ -1,3 +1,4 @@
+---
 nav:
     - index.md
     - "CJK reading distance": cjkReadingDistance.md
@@ -28,4 +29,4 @@ nav:
     - "Starts with": startsWith.md
     - "String equality": equality.md
     - "Substring comparison": substringDistance.md
-    - "Token-wise distance": tokenwiseDistance.md
+    - "Token-wise distance": tokenwiseDistance.md
diff --git a/docs/build/reference/transformer/.pages b/docs/build/reference/transformer/.pages
@@ -1,3 +1,4 @@
+---
 nav:
     - index.md
     - "Combine": Combine
@@ -23,4 +24,4 @@ nav:
     - "Uncategorized": Uncategorized
     - "Validation": Validation
     - "Value": Value
-    - "Variables": Variables
+    - "Variables": Variables
diff --git a/docs/build/reference/transformer/Combine/.pages b/docs/build/reference/transformer/Combine/.pages
@@ -1,6 +1,7 @@
+---
 nav:
     - "Concatenate": concat.md
     - "Concatenate multiple values": concatMultiValues.md
     - "Concatenate pairwise": concatPairwise.md
     - "Merge": merge.md
-    - "Zip": zip.md
+    - "Zip": zip.md
diff --git a/docs/build/reference/transformer/Conditional/.pages b/docs/build/reference/transformer/Conditional/.pages
@@ -1,7 +1,8 @@
+---
 nav:
     - "Contains all of": containsAllOf.md
     - "Contains any of": containsAnyOf.md
     - "If contains": ifContains.md
     - "If exists": ifExists.md
     - "If matches regex": ifMatchesRegex.md
-    - "Negate binary (NOT)": negateTransformer.md
+    - "Negate binary (NOT)": negateTransformer.md
diff --git a/docs/build/reference/transformer/Conversion/.pages b/docs/build/reference/transformer/Conversion/.pages
@@ -1,2 +1,3 @@
+---
 nav:
-    - "Convert charset": convertCharset.md
+    - "Convert charset": convertCharset.md
diff --git a/docs/build/reference/transformer/Date/.pages b/docs/build/reference/transformer/Date/.pages
@@ -1,3 +1,4 @@
+---
 nav:
     - "Compare dates": compareDates.md
     - "Current date": currentDate.md
@@ -8,4 +9,4 @@ nav:
     - "Duration in years": durationInYears.md
     - "Number to duration": numberToDuration.md
     - "Parse date pattern": parseDate.md
-    - "Timestamp to date": timeToDate.md
+    - "Timestamp to date": timeToDate.md
diff --git a/docs/build/reference/transformer/Excel/.pages b/docs/build/reference/transformer/Excel/.pages
@@ -1,3 +1,4 @@
+---
 nav:
     - "Excel Abs": Excel_ABS.md
     - "Excel Acos": Excel_ACOS.md
@@ -111,4 +112,4 @@ nav:
     - "Excel Var": Excel_VAR.md
     - "Excel Vara": Excel_VARA.md
     - "Excel Varp": Excel_VARP.md
-    - "Excel Varpa": Excel_VARPA.md
+    - "Excel Varpa": Excel_VARPA.md
diff --git a/docs/build/reference/transformer/Extract/.pages b/docs/build/reference/transformer/Extract/.pages
@@ -1,2 +1,3 @@
+---
 nav:
-    - "Regex extract": regexExtract.md
+    - "Regex extract": regexExtract.md
diff --git a/docs/build/reference/transformer/Filter/.pages b/docs/build/reference/transformer/Filter/.pages
@@ -1,8 +1,9 @@
+---
 nav:
     - "Filter by length": filterByLength.md
     - "Filter by regex": filterByRegex.md
     - "Remove default stop words": removeDefaultStopWords.md
     - "Remove empty values": removeEmptyValues.md
     - "Remove remote stop words": removeRemoteStopWords.md
     - "Remove stop words": removeStopWords.md
-    - "Remove values": removeValues.md
+    - "Remove values": removeValues.md
diff --git a/docs/build/reference/transformer/Geo/.pages b/docs/build/reference/transformer/Geo/.pages
@@ -1,4 +1,5 @@
+---
 nav:
     - "Retrieve coordinates": RetrieveCoordinates.md
     - "Retrieve latitude": RetrieveLatitude.md
-    - "Retrieve longitude": RetrieveLongitude.md
+    - "Retrieve longitude": RetrieveLongitude.md
diff --git a/docs/build/reference/transformer/Linguistic/.pages b/docs/build/reference/transformer/Linguistic/.pages
@@ -1,6 +1,7 @@
+---
 nav:
     - "Metaphone": metaphone.md
     - "Normalize chars": normalizeChars.md
     - "NYSIIS": NYSIIS.md
     - "Soundex": soundex.md
-    - "Stem": stem.md
+    - "Stem": stem.md
diff --git a/docs/build/reference/transformer/Metadata/.pages b/docs/build/reference/transformer/Metadata/.pages
@@ -1,4 +1,5 @@
+---
 nav:
     - "File hash": fileHash.md
     - "Input file attributes": inputFileAttributes.md
-    - "Input task attributes": inputTaskAttributes.md
+    - "Input task attributes": inputTaskAttributes.md
diff --git a/docs/build/reference/transformer/Normalize/.pages b/docs/build/reference/transformer/Normalize/.pages
@@ -1,3 +1,4 @@
+---
 nav:
     - "Camel case": camelCase.md
     - "Capitalize": capitalize.md
@@ -12,4 +13,4 @@ nav:
     - "Sort words": sortWords.md
     - "Strip non-alphabetic characters": alphaReduce.md
     - "Trim": trim.md
-    - "Upper case": upperCase.md
+    - "Upper case": upperCase.md
diff --git a/docs/build/reference/transformer/Numeric/.pages b/docs/build/reference/transformer/Numeric/.pages
@@ -1,3 +1,4 @@
+---
 nav:
     - "Aggregate numbers": aggregateNumbers.md
     - "Compare numbers": compareNumbers.md
@@ -7,4 +8,4 @@ nav:
     - "Logarithm": log.md
     - "Normalize physical quantity": PhysicalQuantitiesNormalizer.md
     - "Numeric operation": numOperation.md
-    - "Numeric reduce": numReduce.md
+    - "Numeric reduce": numReduce.md
diff --git a/docs/build/reference/transformer/Parser/.pages b/docs/build/reference/transformer/Parser/.pages
@@ -1,3 +1,4 @@
+---
 nav:
     - "Parse date": DateTypeParser.md
     - "Parse float": FloatTypeParser.md
@@ -6,4 +7,4 @@ nav:
     - "Parse integer": IntegerParser.md
     - "Parse ISIN": IsinParser.md
     - "Parse SKOS term": SkosTypeParser.md
-    - "Parse string": StringParser.md
+    - "Parse string": StringParser.md
diff --git a/docs/build/reference/transformer/Replace/.pages b/docs/build/reference/transformer/Replace/.pages
@@ -1,6 +1,7 @@
+---
 nav:
     - "Excel map": excelMap.md
     - "Map": map.md
     - "Map with default": mapWithDefaultInput.md
     - "Regex replace": regexReplace.md
-    - "Replace": replace.md
+    - "Replace": replace.md
diff --git a/docs/build/reference/transformer/SPARQL/.pages b/docs/build/reference/transformer/SPARQL/.pages
@@ -1,3 +1,4 @@
+---
 nav:
     - "Escape SPARQL multiline literal": escape_multiline_literal.md
-    - "Escape SPARQL plain literal": escape_literal.md
+    - "Escape SPARQL plain literal": escape_literal.md
diff --git a/docs/build/reference/transformer/Selection/.pages b/docs/build/reference/transformer/Selection/.pages
@@ -1,3 +1,4 @@
+---
 nav:
     - "Coalesce (first non-empty input)": coalesce.md
-    - "Regex selection": regexSelect.md
+    - "Regex selection": regexSelect.md
diff --git a/docs/build/reference/transformer/Sequence/.pages b/docs/build/reference/transformer/Sequence/.pages
@@ -1,5 +1,6 @@
+---
 nav:
     - "Count values": count.md
     - "Get value by index": getValueByIndex.md
     - "Sequence values to indexes": toSequenceIndex.md
-    - "Sort": sort.md
+    - "Sort": sort.md
diff --git a/docs/build/reference/transformer/Substring/.pages b/docs/build/reference/transformer/Substring/.pages
@@ -1,6 +1,7 @@
+---
 nav:
     - "Strip postfix": stripPostfix.md
     - "Strip prefix": stripPrefix.md
     - "Strip URI prefix": stripUriPrefix.md
     - "Substring": substring.md
-    - "Until character": untilCharacter.md
+    - "Until character": untilCharacter.md
diff --git a/docs/build/reference/transformer/Template/.pages b/docs/build/reference/transformer/Template/.pages
@@ -1,2 +1,3 @@
+---
 nav:
-    - "Evaluate template": TemplateTransformer.md
+    - "Evaluate template": TemplateTransformer.md
diff --git a/docs/build/reference/transformer/Tokenization/.pages b/docs/build/reference/transformer/Tokenization/.pages
@@ -1,3 +1,4 @@
+---
 nav:
     - "Camel case tokenizer": camelcasetokenizer.md
-    - "Tokenize": tokenize.md
+    - "Tokenize": tokenize.md