This repository contains the artifacts for a specification that defines composite data types (CDTs) to represent lists and maps as literals in RDF data, and extends the SPARQL query language with features related to these CDTs. These features include
- an aggregation function to produce such composite values,
- functions to operate on the composite values in expressions, and
- a new operator to unfold the composite values into their individual components.
The latest version of the specification document, which includes an informal description of the approach, is published under the following permanent identifier:
- The spec directory contains the various versions of the specification document, including the editors' draft. If you want to look at the current snapshot of the editors' draft directly in your browser, use the following permanent address: https://w3id.org/awslabs/neptune/SPARQL-CDTs/spec/editors_draft.html
- The tests directory contains a test suite with a comprehensive collection of tests that developers of RDF and SPARQL systems can use to check whether their implementation of the different features defined in the specification is correct.
We have extended the Java-based RDF programming framework Apache Jena with a complete implementation of all the features defined in the specification. This extension has become part of the official Jena releases in version 5.2.0.
To try this implementation, download the latest release of Jena, unpack it, and use the ARQ command line programs of Jena to run SPARQL queries that use the features defined in the specification.
Alternatively, and even easier, you can also simply run such SPARQL queries via the online SPARQL query processor at https://sparql.org/, which is built on Jena. As an initial example, you may try the following query for which you do not even need a file with RDF data.
PREFIX cdt: <http://w3id.org/awslabs/neptune/SPARQL-CDTs/>
PREFIX ex: <http://example.org/>
SELECT ?list3 ?elmt ?key ?value WHERE {
BIND( "[1, 'hello'@en]"^^cdt:List AS ?list1 ) # provide the literal directly
BIND( cdt:List(ex:test, 42) AS ?list2 ) # or use the cdt:List constructor
BIND( cdt:concat(?list1, ?list2) AS ?list3 )
BIND( cdt:get(?list3, 3) AS ?elmt )
UNFOLD( "{ 'hello': 'world' }"^^cdt:Map AS ?key, ?value )
}
We have also extended the Perl-based RDF programming framework Attean with a complete implementation of the specification. This extension has become part of Attean version 0.034.
We are working on a collection of command-line tools related to the approach. Currently, it contains a tool to convert RDF data that uses RDF collections to RDF data in which the collections are replaced by cdt:List literals. The relevant repository is: https://github.com/hartig/SPARQL-CDT-Tools
DCM2RDF is tool that extracts metadata from DICOM files and converts this metadata into an RDF representation. Since version 1.1.0, the tool supports the option to use cdt:List literals to represent any array-like structure that exists in DICOM.
If you have another implementation, let us know!
- SEP-0009, which is a SPARQL Enhancement Proposal of the approach, submitted to the SPARQL-DEV Community Group