ShEx: Shape Expression language for Ruby

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

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  • 100% pure Ruby with minimal dependencies and no bloat.
  • Fully compatible with ShEx specifications.
  • 100% free and unencumbered public domain software.


The ShEx gem implements a ShEx Shape Expression engine.

  • ShEx::Parser parses ShExC formatted documents generating executable operators which can be serialized as S-Expressions.
  • ShEx::Algebra executes operators against Any RDF::Graph, including compliant RDF.rb.


require 'rubygems'
require 'rdf/turtle'
require 'shex'

shexc: %(
  PREFIX doap:  <>
  PREFIX dc:    <>
  <TestShape> EXTRA a {
    a doap:Project;
    doap:developer IRI;
    doap:implements    [<>]
graph = RDF::Graph.load("etc/doap.ttl")
schema = ShEx.parse(shexc)
map = {
  "" => "TestShape"
schema.satisfies?("", graph, map)
# => true


Implementation Notes

The ShExC parser uses the EBNF gem to generate first, follow and branch tables, and uses the Parser and Lexer modules to implement the ShExC parser.

The parser takes branch and follow tables generated from the ShEx Grammar described in the specification. Branch and Follow tables are specified in the generated ShEx::Meta.



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

% [sudo] gem install shex


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

% git clone git://

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

% wget


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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][YARD-GS] 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][PDD] on record from you.


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