SHACL: Shapes Constraint Language (SHACL) for Ruby

This is a pure-Ruby library for working with the Shape Constraint Language to validate the shape of RDF graphs.

Features

  • 100% pure Ruby with minimal dependencies and no bloat.

  • Fully compatible with SHACL specifications.

  • 100% free and unencumbered public domain software.

Implementation Report

Install with gem install shacl

Description

The SHACL gem implements a SHACL Shape Expression engine.

Examples

require 'linkeddata'
require 'shacl'

graph = RDF::Graph.load("etc/doap.ttl")
shacl = SHACL.open("etc/doap.shacl")
report = shacl.execute(graph)
#=> ValidationReport(conform?, results*)

Command Line

TODO: When the linkeddata gem is installed, RDF.rb includes a rdf executable which acts as a wrapper to perform a number of different operations on RDF files, including SHACL. The commands specific to SHACL is

*shacl: Validate repository given shape

Using this command requires shacl, which references a URI or file path to the SHACL shapes graph. Other options are shape and focus.

Example usage:

rdf shacl https://ruby-rdf.github.io/shacl/etc/doap.ttl \
  --shape https://ruby-rdf.github.io/shacl/etc/doap-shape.ttl

The result will add the SHACL validation report to the output graph, optionally replacing the graph with the results, expressing the results as an s-expression, or adding the results as output messages.

Documentation

ruby-rdf.github.io/shacl

Implementation Notes

Similar to the ShEx gem and to the general strategy for querying graphs in the SPARQL gem, the strategy is to parse SHACL shapes into executable operators, which are called recursively to create result sets corresponding to matched nodes and properties.

The shape graph is parsed into JSON-LD, and then converted into S-Expressions, which match the execution path. These S-Expressions can be parsed to recreate the executable shape constraints.

Evaluating the shapes against a graph results in a SHACL::ValidationReport indicating conformance, along with a set of individual SHACL::ValidationResult instances.

The resulting validation report can be compared with other validation reports, used as native Ruby objects, serialized to s-expressions, or used as an RDF::Enumerable to retrieve the RDF representation of the report, as defined in SHACL Spec.

Matching Entailed Triples

Many tests check for entailed triples, such as entailed super-classes of explicit rdf:type values. If this is required for a given application, the RDF::Reasoner gem can be used to create such entailed triples.

require 'shacl'
require 'rdf/reasoner'
RDF::Reasoner.apply(:rdfs)
graph = RDF::Graph.load("etc/doap.ttl")
graph.entail!
shacl = SHACL.open("etc/doap.shacl")
results = shacl.execute(graph)
#=> [ValidationResult, ...]

Future work

This implementation is certainly not performant. Some things that can be be considered in future versions:

  • Support for SHACL-SPARQL

  • Index shapes on targetNode and targetClass and other targets to allow a more efficient query to find relevant resources in the data graph and not simply iterrate through each top-level shape.

  • Cache target nodes as JSON-LD to reduce the need to separately query for each constraint.

  • Reasoner should support limited RDFS/OWL entailment from the data graph, not just pre-defined vocabularies.

Dependencies

Installation

The recommended installation method is via RubyGems. To install the latest official release of RDF.rb, do:

% [sudo] gem install shacl

Download

To get a local working copy of the development repository, do:

% git clone git://github.com/ruby-rdf/shacl.git

Alternatively, download the latest development version as a tarball as follows:

% wget https://github.com/ruby-rdf/shacl/tarball/master

Resources

Mailing List

Author

Contributing

This repository uses Git Flow to mange development and release activity. All submissions must be on a feature branch based on the develop branch to ease staging and integration.

  • Do your best to adhere to the existing coding conventions and idioms.

  • Don’t use hard tabs, and don’t leave trailing whitespace on any line. Before committing, run git diff --check to make sure of this.

  • Do document every method you add using YARD annotations. Read the tutorial or just look at the existing code for examples.

  • Don’t touch the .gemspec or VERSION files. If you need to change them, do so on your private branch only.

  • Do feel free to add yourself to the CREDITS file and the corresponding list in the the README. Alphabetical order applies.

  • Don’t touch the AUTHORS file. If your contributions are significant enough, be assured we will eventually add you in there.

  • Do note that in order for us to merge any non-trivial changes (as a rule of thumb, additions larger than about 15 lines of code), we need an explicit public domain dedication on record from you, which you will be asked to agree to on the first commit to a repo within the organization. Note that the agreement applies to all repos in the Ruby RDF organization.

License

This is free and unencumbered public domain software. For more information, see unlicense.org/ or the accompanying LICENSE file.