skolemizer

A library with utils for performing Skolemization on blank nodes (RDF)

W3C has a short intro to skolemization here: https://www.w3.org/2011/rdf-wg/wiki/Skolemisation

Development

Requirements

• pyenv (recommended)
• pipx (recommended)
• poetry
• nox
• nox-poetry

% pipx install poetry==1.1.6
% pipx install nox==2020.12.31
% pipx inject nox nox-poetry

Install

% git clone https://github.com/Informasjonsforvaltning/skolemizer.git
% cd skolemizer
% pyenv install 3.9.4
% pyenv local 3.9.4
% poetry install

Getting started

Remember before starting to always set the baseurl for skolemization, according to your organization url. This can be done by setting the environment variable skolemizer_baseurl on your operating system. It can also e.g. be done run time through Python's os package:

os.environ[Skolemizer.baseurl_key] = "https://www.someorganiztion.somedomain/"

If not set Skolemizer will use "http://example.com/" as base url. In order to invoke the skolemizer for ensuring identifier of rdf-nodes simply add

from skolemizer import Skolemizer

and then before rdf-serialization of a class:

        if not getattr(self, "identifier", None):
            self.identifier = Skolemizer.add_skolemization()

There should also be a skolemization check performed when serializing object properties. When creating unit tests of skolemized rdf nodes an uuid will be applied as a substring of the complete skolemization. Therefore, in order to create stable unit tests one can use the tests utils in order to mock a stable skolemization.

E.g. pytest-mocks MockFixture permits mocking of the skolemizer:

    from pytest_mock import MockFixture
    from skolemizer.testutils import skolemization

    catalog = Catalog()

    mocker.patch(
        "skolemizer.Skolemizer.add_skolemization",
        return_value=skolemization
    )

which outputs e.g:

        @prefix dct: <http://purl.org/dc/terms/> .
        @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
        @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
        @prefix dcat: <http://www.w3.org/ns/dcat#> .

        <http://wwww.digdir.no/.well-known/skolem/284db4d2-80c2-11eb-82c3-83e80baa2f94>
         a dcat:Catalog  .

Run all sessions

% nox

Run all tests with coverage reporting

% nox -rs tests

Debugging

You can enter into Pdb by passing --pdb to pytest:

nox -rs tests -- --pdb

You can set breakpoints directly in code by using the function breakpoint().