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Introduction

Based off the work of @barmintor's rdf-digest. RdfHashing is a PHP implementation of the Höfig/Schieferdecker RDF hashing algorithm described in Hashing of RDF Graphs and a Solution to the Blank Node Problem.

See also my Java implementation at rdf-hashing-java

It generates a specifically formatted string based on the above paper and then a SHA-256 hash of that string.

Installation

Install using composer

composer install

Usage

This comes as a small library for inclusion in other applications, but we also include a simple command line script to test it out

Library

The RdfHashing class provides two static methods.

  • RdfHashing::calculate(graph) takes an \EasyRdf\Graph and returns the hexadecimal sha256 hash.
  • RdfHashing::getGraphString(graph) takes an \EasyRdf\Graph and returns the parsed formatted string of the graph ready to generate the hash.
<?php

use RdfHash\RdfHashing;
use EasyRdf\Graph;

$graph = new Graph();
$graph->parseFile("/some/file/of/RDF.ttl");

$rdf_hash = RdfHashing::calculate($graph);

Command line

A script rdfhash allows you to try parse a file or URL to generate a RDF hash.

> ./rdfhash
You must provide a source path or url

Usage: rdfhash --source
  --source : file or url of rdf source

Providing a file path or URL should result in a hash for the found RDF.

> ./rdfhash --source=./tests/resources/supersimple.ttl                                                                 
c3f2f988a2e339eb6622ba2fe0d6452fffb1b123fed947ba66900d89b6e3ab5c

You can also pass the --debug argument to see the graph string before it is hashed.

> ./rdfhash --source=./tests/resources/supersimple.ttl --debug
{*(http://ex#pred[*(http://ex#pred[http://ex#A][http://ex#C])][http://ex#C])}{*(http://ex#pred[*(http://ex#pred[http://ex#B][http://ex#C])][http://ex#C])}{*(http://ex#pred[http://ex#A][http://ex#C])}{*(http://ex#pred[http://ex#B][http://ex#C])}
c3f2f988a2e339eb6622ba2fe0d6452fffb1b123fed947ba66900d89b6e3ab5c

License

  • MIT