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This library allows to convert YARRRML rules to RML or R2RML rules.


  • npm i -g @rmlio/yarrrml-parser



There are two CLI functions, yarrrml-parser and yarrrml-generator. Using the --help flag will show all possible commands.


If you want to generate RML rules from a YARRRML document, you do the following: yarrrml-parser -i rules.yml.

The rules will be written to standard output. If you want to write them to a file, you can add the -o option.

By default, the parser generates RML rules. If you want to generate R2RML rules add -f R2RML.

If you want to use rr:class instead of Predicate Object Maps, use the -c flag.

You can use multiple input files too: yarrrml-parser -i rules-1.yml -i rules-2.yml. They are converted to a single RML document. Note that the keys in prefixes, sources, and mappings have to be unique across all files. base can only be set once. You find an example at test/multiple-input-files.

You can overwrite external references via the -e. An external reference starts with _. For example, -e name=John will replace all occurrences of $(_name) with John. Repeat -e for multiple references. When you do not provide a value for an external reference, the reference will not be replaced. You find an example in test/template-escape. If you want to use for example $(_name) as both an external reference and a normal reference, then you add a \ for the latter resulting in $(\_name) for the latter.

If you want the outputted RML to be pretty, please provide the -p or --pretty parameter.


If you want to generate YARRRML rules from an RML document, you do the following: yarrrml-generator -i rules.rml.ttl. The rules will be written to standard output. If you want to write them to a file, you can add the -o option.


npm i --save @rmlio/yarrrml-parser

let yarrrml = require('@rmlio/yarrrml-parser/lib/rml-generator');

const yaml = "[yarrrml string]";
const y2r = new yarrrml();
const triples = y2r.convert(yaml);

if ( y2r.getLogger().has('error') ) {
   const logs = y2r.getLogger().getAll();


  • Clone this repo.
  • Install the dependencies via npm i
  • Update code, if needed.
  • Run the tests via npm test
    • If you make a new test, make sure the (RML) Turtle is 'pretty'. If you're not sure it's pretty, run ./test/prettify_ttl.js
  • Make the CLI (based on the code in the cloned repo) available system-wide via npm link (optional).


Run (from DockerHub):

docker run --rm -it -v $(pwd)/resources:/data rmlio/yarrrml-parser:latest -i /data/test.yarrr.yml

Build from source:

docker build -t yarrrml-parser .


This code is copyrighted by Ghent University – imec and released under the MIT license.