Linked Data Extension

The Elsevier Data Architecture Linked Data Extension (LDE) for Visual Studio Code brings a number of Linked Data related functionalities to a popular integrated development environment.

It's not industry-grade solid, but should be good enough™. For any questions, comments, please contact Rinke Hoekstra, or create an issue in the GitHub repository.

What it does

• Visualise an RDF graph directly from a file.
• Convert between JSON-LD, Turtle, RDF/XML and N-Quads (some quirks because not every format supports named graphs)
• Convert between JSON-LD variants (compact, expanded, flattened)
• Apply a JSON-LD frame to a JSON-LD file.
• Validate your RDF against a SHACL file
• Run a SPARQL query directly on a file and see the results in HTML and CSV

The JSON-LD operations can work with local context files. This overcomes the limitation in most JSON-LD libraries that interpret context references as URLs. See the loadLocalContexts setting below.

Download Linked Data Extension from https://marketplace.visualstudio.com/items?itemName=Elsevier.linked-data or through the Extensions menu of VSCode.

This extension depends on the Stardog Languages Extension Pack from Stardog Union for file type recognition, syntax highlighting and syntax checking.

Screenshots

For the files used in the screenshots, see the examples folder.

Conversion Between RDF Formats

Visualisation and JSON-LD Variants

SPARQL and SHACL

Commands

You can access the commands through the command palette: Cmd-Shift-p or Ctrl-Shift-p and then start typing "Linked Data", or use one of the following keyboard shortcuts.

Keyboard Shortcuts

• Standard syntactic JSON-LD operations:
  • Ctrl-Option-e/Ctrl-Alt-e: Convert a JSON-LD structure to the expanded document form
  • Ctrl-Option-c/Ctrl-Alt-c: Apply @context specifications to convert a JSON-LD structure to the compacted document form. Only works with an included context (not external files)
  • Ctrl-Option-l/Ctrl-Alt-l: Convert a JSON-LD structure to the flattened document form
  • Ctrl-Option-f/Ctrl-Alt-f: Apply a JSON-LD frame file to convert a JSON-LD structure to the framed document form using the framing algorithm.
• Standard format conversions:
  • Ctrl-Option-n/Ctrl-Alt-n: Convert an RDF file (any format) to N-Quads
  • Ctrl-Option-t/Ctrl-Alt-t: Convert an RDF file (any format) to Turtle (may be lossy for files that contain multiple graphs)
  • Ctrl-Option-r/Ctrl-Alt-r: Convert an RDF file (any format) to RDF/XML (may be lossy for files that contain multiple graphs)
  • Ctrl-Option-j/Ctrl-Alt-j: Convert an RDF file (any format) to JSON-LD
• View as a Graph:
  • Ctrl-Option-g/Ctrl-Alt-g: Render an RDF file as a D3js force directed graph.
• Validate against SHACL shapes:
  • Ctrl-Option-v/Ctrl-Alt-v: Validate an RDF file against SHACL shapes (see below)
• Query a Graph:
  • Ctrl-Option-q/Ctrl-Alt-q: Run the SPARQL query against an RDF file (see below)

Extension Settings

This extension contributes the following settings:

• linked-data.loadLocalContexts: Should the extension try to load local (non-URI) JSON-LD context files. This is especially useful when testing large context files that are intended to be shared across multiple JSON-LD files. It overcomes the problem that JSON-LD libraries interpret references to contexts as URIs, which would require running an HTTP server to test the context.

Tips and Recommendations

SHACL Validator

The SHACL Validator can be told what shapes file to use, by adding commented lines to the top of a Turtle file (does not work for JSON-LD) that refer to a (relative path) to the shapes file using the shapes attribute, e.g. the following will try to load the my_excellent_shapes.ttl file.

# shapes: my_excellent_shapes.ttl
@prefix ex: <https://example.com/> .

ex:Alice
	a ex:Person ;
	ex:ssn "987-65-432A" .

If there is no such instruction, or the instruction cannot be parsed as YAML, the extension will show a file open window for you to select the shapes file to use.

SPARQL Query

You can run a SPARQL Query only from valid SPARQL files (*.rq), and similar to the SHACL validator, you can specify the file against which you want to run the query by using the file attribute:

# file: example-1-transformed/source.json
SELECT * WHERE  {
    ?a ?b ?c .
}

If there is no such instruction, or the instruction cannot be parsed as YAMLM, the extension will show a file open window for you to select the RDF file to query against.

SPARQL results are shown both as a web view with a table that supports sorting and search, as well as a CSV file for further processing.

Known Limitations

• RDF format support is limited to the underlying libraries. E.g RDF/XML support is spotty as it doesn't deal with XML entity definitions very well.

Thanks go to:

• Stardog VSCode Extensions, https://github.com/stardog-union/stardog-vsc
• rdflib.js, https://github.com/linkeddata/rdflib.js/
• Zazuko's SHACL validator, https://github.com/zazuko/rdf-validate-shacl
• Google's Schemarama, https://github.com/google/schemarama
• d3js, https://d3js.org
• ... and many others.