R2RML Implementation

Building and using the code

To build the project and copy its dependencies, execute

$ mvn package
$ mvn dependency:copy-dependencies

Note: in order to support connection to Oracle databases, we rely on a library that is not available from the Maven repository. If you have that library not installed manually, run mvn clean before mvn package and it will install the library locally prior to packaging.

The run the R2RML processor, execute the following command:

$ java -jar r2rml.jar config.properties

A fat jar is also provided with the Apache Maven Shade Plugin. It does not depend on the dependency folder and can be executed as follows:

$ java -jar r2rml-fat.jar config.properties

Where config.properties is a properties file 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:mysql://localhost/r2rml
user = foo
password = bar
mappingFile = mapping.ttl
outputFile = output.ttl
format = TURTLE

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" .

Run with command line arguments

R2RML can be run with command line arguments similar to the configuration properties.

$ java -jar r2rml.jar --connectionURL jdbc:mysql://localhost/r2rml \
  --user foo --password bar \
  --mappingFile mapping.ttl \
  --outputFile output.ttl \
  --format TURTLE

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 ;
	}
	""" ;
.

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