vemonet/r2rml repository overview

⁠R2RML Implementation

⁠Building and using the code

⁠To build the project and copy its dependencies, execute

$ docker build -t r2rml .

⁠The run the R2RML processor, execute the following command:

$ docker run -it --rm --link some-progress:my-progress -v <local dir>:/data r2rml /data/config.properties

Hint: check out official postgresql docker documentation⁠

Where config.properties is a properties file (in this case mapped through /data to you local dir) containing:

• connectionURL, a JDBC connection URL to a database (required)
• user, username for the user connecting to the database
• password, password for the user connecting to the database
• mappingFile, the R2RML mapping file (required)
• outputFile, the output file (required)
• format, format of the output files (default "TURTLE")
• filePerGraph, flag to write the different graphs in separate files (default "false")
• baseIRI, used in resolving relative IRIs produced by the R2RML mapping
• CSVFiles, a list of paths to CSV files that are separated by semicolons.

When named graphs are used in the R2RML mapping, one should use serialization that support graphs such as N-QUADS and TRIG. The use of other serializations formats (such as TURTLE) results in all triples of all graphs being written away to that file. When setting the flag filePerGraph to true for serialization formats that do not support graphs, however, the value for outputFile will be used to create a directory in which a file will be created for each graph in the RDF dataset.

Note that you cannot use both CSVFiles and connectionURL at the same time. For each CSV file, the name of the table will be the base name of that file.

⁠Example

The directory example contains an example of a mapping and configuration file. The example assumes the MySQL database to be called r2rml, be running on localhost and accessible to the user foo with password bar. The configuration file looks as follows:

connectionURL = jdbc:postgresql://my-postgres:5432/<db_name>
user = foo
password = bar
mappingFile = /data/mapping.ttl
outputFile = /data/output.ttl.gz
format = TURTLE

Hint: my-postgres is the name of the link from the docker command above

The output, after passing the properties file as an argument to the R2RML processor, should look as follows:

<http://data.example.com/employee/7369>
        a                             <http://example.com/ns#Employee> ;
        <http://example.com/ns#name>  "SMITH" .

⁠Function with R2RML-F

This implementation of R2RML re-implemented the ideas presented in [1], allowing one to declare and use functions in ECMAScript as (Function Valued) TermMaps in the mapping. R2RML-F extends R2RML's vocabulary with predicates for declaring functions, function calls and parameter bindings. These are declared in the namespace rrf⁠.

@prefix rr: <http://www.w3.org/ns/r2rml#> .
@prefix ex: <http://example.com/ns#> .
@prefix rrf: <http://kdeg.scss.tcd.ie/ns/rrf#>

<#TriplesMap1>
    rr:logicalTable [ rr:tableName "EMP" ];
    rr:subjectMap [
        rr:template "http://data.example.com/employee/{EMPNO}";
        rr:class ex:Employee;
    ];
    rr:predicateObjectMap [
        rr:predicate ex:name;
        rr:objectMap [ rr:column "ENAME" ];
    ];
    rr:predicateObjectMap [
        rr:predicate ex:test;
        rr:objectMap [
	        rrf:functionCall [
	 			rrf:function <#Concat> ;
	 			rrf:parameterBindings (
	 				[ rr:column "ENAME" ]
	 				[ rr:column "EMPNO" ]
	 			) ;
	 		] ; 
	 	]
    ]    
    .
    
<#Concat>
	rrf:functionName "concat" ;
	rrf:functionBody """
		function concat(var1, var2) {
		return var1 + " " + var2 ;
	}
	""" ;
.

⁠Run using command line parameters

# Start Apache Drill
docker run -dit --rm -p 8047:8047 -p 31010:31010 --name drill -v /data:/data:ro maastrichtuids/apache-drill

# Run R2RML
docker run -it --rm --link drill:drill -v /data:/data maastrichtuids/r2rml \ 
  --connectionURL jdbc:drill:drillbit=drill:31010 \
  --mappingFile /data/mapping.trig \
  --outputFile /data/rdf_output.nq \
  --format NQUADS

⁠License

This implementation of R2RML is written by Christophe Debruyne⁠ and released under the MIT license⁠.

⁠References

[1] C. Debruyne and D. O'Sullivan. R2RML-F: Towards Sharing and Executing Domain Logic in R2RML Mappings. In Proceedings of the Workshop on Linked Data on the Web, LDOW 2016, co-located with the 25th International World Wide Web Conference (WWW 2016), Montreal, Canada, April 12th, 2016, 2016