How to write a plugin

What is a plugin?

A plugin is a software component that adds a specific feature to an existing computer program. When a program supports plug-ins, it enables customization (Wikipedia).

In the context of OAK, plugins allow you to add optional functionality to OAK.

An example of a plugin would be a code that uses a machine learning library such as Spacy or NLTK to provide an implementation of a text_annotator. We wouldn’t want to include this in the main library due to the additional dependencies required. But we might want to allow people to drop in this functionality, e.g.

runoak -i my_awesome_plugin: annotate "my text here"

An example plugin

oakx-robot is a plugin that implements the validator interface, providing access to OWL reasoners through robot.

You can use this programmatically by first installing it:

pip install oakx-robot

And then using the plugin’s selector, which is robot:

runoak -i robot:tests/input/go-nucleus-unsat.owl validate

This can also be used programmatically

from oaklib.selector import get_resource_from_shorthand, discovered_plugins, get_adapter
from oakx_robot.robot_implementation import RobotImplementation, OWL_NOTHING

path = 'tests/input/go-nucleus-unsat.owl'
oi = get_adapter(f'robot:{path}')
if oi.is_coherent():
    print('Congratulations! The ontology is coherent')
    print('Reasoner detected usatisfiable classes')
    for c in oi.unsatisfiable_classes():
        print(f'Unsatisfiable: {c}')

Creating a plugin

Discuss on the issue tracker

First make an issue on the OAK issue tracker - someone may be developing a plugin similar to yours! You will also want to propose the namespace/scheme you will use.

Create a new project

First create a new python project in the way you would normally do this.

We recommend using poetry, but you can adapt these to whichever system you like:

poetry new --src oakx-my-awesome-plugin

The project name should always start with oakx-. Remember, poetry will make a python project that uses underscores in the name

Then make sure OAK is added as a dependency:

poetry add oaklib

Implement one or more interfaces

  1. Create an Implementation Class

  2. Have this implement at least one interface

  3. Implement __post_init__(), which initializes the implementation using a Resource object.


oakx-robot implementation

Implement a selector

OAK recognizes plugins by looking for entry points in the oaklib.plugins group. The name of each entry point should be the selector scheme you implement, and the object reference of the entry point should be the corresponding implementation. The scheme should match the name used for your project, and should be unique, concise, and descriptive. Don’t pollute the top level namespace!

The way you specify entry points will depend on the packaging tool your project uses. When using Poetry, your project would include something like the following in pyproject.toml:

robot = "oakx_robot.robot_implementation:RobotImplementation"

If your project does not use Poetry, consult your build tool’s documentation for information on how to implement an entry point (e.g. using setuptools).

Write tests

Write tests as you would for any other project

See for example oakx-robot tests

Release to PyPI

Release to PyPI as you would any other module. E.g. with poetry:

poetry publish