A package for ontology-oriented programming in Python: load OWL 2.0 ontologies as Python objects, modify them, save them, and perform reasoning via HermiT. Includes an optimized RDF quadstore.

pip install Owlready2==0.35



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Owlready2 is a module for ontology-oriented programming in Python 3, including an optimized RDF quadstore.

Owlready2 can:

  • Import OWL 2.0 ontologies in NTriples, RDF/XML or OWL/XML format.
  • Export OWL 2.0 ontologies to NTriples or RDF/XML.
  • Manipulates ontology classes, instances and properties transparently, as if they were normal Python objects.
  • Add Python methods to ontology classes.
  • Perform automatic classification of classes and instances, using the HermiT reasoner.
  • Tested up to 200 millions of RDF triples (but can potentially support more).
  • In addition, the quadstore is compatible with the RDFlib Python module, which can be used to perform SPARQL queries.
  • Finally, Owlready2 can also be used as an ORM (Object-Relational mapper) or an object database.

Owlready has been created by Jean-Baptiste Lamy at the LIMICS reseach lab. It is available under the GNU LGPL licence v3. If you use Owlready in scientific works, please cite the following article:

Lamy JB. Owlready: Ontology-oriented programming in Python with automatic classification and high level constructs for biomedical ontologies. Artificial Intelligence In Medicine 2017;80:11-28

In case of troubles, questions or comments, please use this Forum/Mailing list: http://owlready.8326.n8.nabble.com

What can I do with Owlready2?

Load an ontology from a local repository, or from Internet:

>>> from owlready2 import *
>>> onto_path.append("/path/to/your/local/ontology/repository")
>>> onto = get_ontology("http://www.lesfleursdunormal.fr/static/_downloads/pizza_onto.owl")
>>> onto.load()

Create new classes in the ontology, possibly mixing OWL constructs and Python methods:

>>> class NonVegetarianPizza(onto.Pizza):
...   equivalent_to = [
...     onto.Pizza
...   & ( onto.has_topping.some(onto.MeatTopping)
...     | onto.has_topping.some(onto.FishTopping)
...     ) ]
...   def eat(self): print("Beurk! I'm vegetarian!")

Access ontology class, and create new instances / individuals:

>>> onto.Pizza
>>> test_pizza = onto.Pizza("test_pizza_owl_identifier")
>>> test_pizza.has_topping = [ onto.CheeseTopping(),
...                            onto.TomatoTopping(),
...                            onto.MeatTopping  () ]

Export to RDF/XML file:

>>> test_onto.save()

Perform reasoning, and classify instances and classes:

>>> test_pizza.__class__

>>> # Execute HermiT and reparent instances and classes
>>> sync_reasoner()

>>> test_pizza.__class__
>>> test_pizza.eat()
Beurk! I'm vegetarian !

For more documentation, look at the doc/ directories in the source.


version 1 - 0.2

  • Fix sync_reasonner and Hermit call under windows (thanks Clare Grasso)

version 1 - 0.3

  • Add warnings
  • Accepts ontologies files that do not ends with '.owl'
  • Fix a bug when loading ontologies including concept without a '#' in their IRI

version 2 - 0.1

  • Full rewrite, including an optimized quadstore

version 2 - 0.2

  • Implement RDFXML parser and generator in Python (no longer use rapper or rdflib)
  • Property chain support
  • Add ntriples_diff.py utility
  • Bugfixes: - Fix breaklines in literal when exporting to NTriples

version 2 - 0.3

  • Add destroy_entity() global function
  • Greatly improve performance for individual creation
  • When searching, allow to use "*" as a jocker for any object
  • Bugfixes: - Fix nested intersections and unions - Fix boolean - Fix bug when removing parent properties - Fix parsing of rdf:ID - Fix multiple loading of the same ontology whose IRI is modified by OWL file, using an ontology alias table - Fix ClassConstruct.subclasses() - Check for properties with multiple incompatible classes (e.g. ObjectProperty and Annotation Property)

version 2 - 0.4

  • Add methods for querying the properties defined for a given individuals, the inverse properties and the relation instances (.get_properties(), .get_inverse_properties() and .get_relations())
  • Add .indirect() method to obtain indirect relations (considering subproperties, transivitity, symmetry and reflexibity)
  • search() now takes into account inheritance and inverse properties
  • search() now accepts 'None' for searching for entities without a given relation
  • Optimize ontology loading by recreating SQL index from scratch
  • Optimize SQL query for transitive quadstore queries, using RECURSIVE Sqlite3 statements
  • Optimize SQL query for obtaining the number of RDF triples (ie len(default_world.graph))
  • Add Artificial Intelligence In Medicine scientific article in doc and Readme
  • Bugfixes: - Fix properties loading when reusing an ontology from a disk-stored quadstore - Fix _inherited_property_value_restrictions() when complement (Not) is involved - Fix restrictions with cardinality - Fix doc on AllDisjoint / AllDifferent

version 2 - 0.5

  • Add individual/instance editor (require EditObj3, still largely untested)
  • Add support for hasSelf restriction
  • Optimize XML parsers
  • Check for cyclic subclass of/subproperty of, and show warning
  • PyPy 3 support (devel version of PyPy 3)
  • Bugfixes: - Fix search() for '*' value on properties with inverse - Fix individual.annotation = "..." and property.annotation = "..." - Fix PlainLiteral annotation with no language specified - Fix doc for Creating classes dynamically - Fix loading ontologies with python_name annotations - Fix _inherited_property_value_restrictions when multiple is-a / equivalent-to are present - Align Python floats with xsd:double rather than xsd:decimal - Rename module 'property' as 'prop', to avoid name clash with Python's 'property()' type

version 2 - 0.6

  • Add set_datatype_iri() global function for associating a Python datatype to an IRI
  • Add nquads ontology format (useful for debugging)
  • Add support for dir() on individuals
  • Add support for ontology using https: protocol (thanks Samourkasidis Argyrios)
  • Add observe module (for registering callback when the ontology is modified)
  • Improve docs
  • Bugfixes: - Align Python floats with xsd:decimal rather than xsd:double, finally, because decimal accepts int too - Fix Class.instances() so as it returns instances of subclasses (as indicated in the doc) - Fix direct assignation to Ontology.imported_ontologies - Fix a bug in reasoning, when adding deduced facts between one loaded and one non-loaded entity

version 2 - 0.7

  • Bugfixes: - Restore HermiT compiled with older Java compilator (higher compatibility)

version 2 - 0.8

  • Bugfixes: - REALLY restore HermiT compiled with older Java compilator (higher compatibility) - Fix search(prop = "value") when value is a string and the ontology uses localized string

version 2 - 0.9

  • PostgresQL backend (in addition to SQLite3)
  • Add 'exclusive = False' option for SQLite3 backend (slower, but allows multiple uses)
  • Use unique index in sqlite3 quadstore on resources table
  • Optimize sqlite3 quadstore by caching IRI dict (5% faster)
  • Add == support for class construct
  • Add get_namespace() support on World
  • Add 'existential restrictions as class properties' feature
  • Bugfixes: - Fix imported ontologies - Fix saving ontologies in onto_path - Fix clear() on CallbackList - Fix bug in Class IRI in ontologies whose base IRI ends with a / - Fix imported ontologies in ontologies whose base IRI ends with a /

version 2 - 0.10

  • Add Ontology.metadata for adding/querying ontology metadata
  • Allows multiple individual creations with the same name/IRI, now returning the same individuals
  • Add OwlReadyInconsistentOntologyError and Word.inconsistent_classes()
  • Implement RDF/XML and OWL/XML parsing in Cython (25% speed boost for parsing)
  • Small optimization
  • Extend individual.prop.indirect() to include relations asserted at the class level
  • Add .query_owlready() method to RDF graph
  • Bugfixes: - Fix reasoning when obtaining classes equivalent to nothing - Fix World creation with backend parameters - Fix error when adding property at the class definition level - Fix loading of ontology files with no extension from onto_path - Fix properties defined with type 'RDF Property' and subproperty of 'OWL Data/Object/Annotation Property' - Support old SQLite3 versions that do not accept WITHOUT ROWID - Fix reference to undeclared entities (they were replaced by None, now by their IRI) - Fix loading and saving ontologies whose base IRI ends with / - Fix RDF query using string

version 2 - 0.11

  • Optimized Full-Text Search
  • Support Pellet reasoner in addition to HermiT
  • Support loading of huge OWL files (incremental load)
  • Use Class.property.indirect() for indirect Class property (instead of Class.property)
  • Add reload and reload_if_newer parameters to Ontology.load()
  • search() is now much faster on properties that have inverse
  • Add shortcut for SOME ConstrainedDatatype: e.g. age >= 65
  • Bugfixes: - Fix creation of an individual that already exists in the quadstore - Fix missing import of EntityClass in class_construct.py - Fix World.save() with RDF/XML format - Fix Thing.subclasses() and Thing.descendants() - Fix ontology's update time for ontologies created de novo in Python with Owlready - Fix reasoning when asserting new parents with equivalent classes

version 2 - 0.12

  • New quadstore
  • Numerical search (NumS, e.g. all patients with age > 65)
  • Nested searches
  • Synchronization for multithreading support
  • Add Class.inverse_restrictions() and Class.direct_instances()
  • Drop PostgresQL support (little interest: more complex and slower than Sqlite3)
  • Bugfixes: - Fix call to _get_by_storid2 - Fix rdfs_subclassof in doc - Fix FTS triggers - Fix boolean in RDFlib / SPARQL - Fix bug when destroying an AnnotationProperty

version 2 - 0.13

  • Bugfixes: - Fix performance regression due to suboptimal index in the quadstore - Fix messing up with IRI ending with a / - Fix error in World cloning - Fix the addition of Thing in class's parent when redefining a class with Thing as the only parent - Fix inverse_resctriction() - Add error message when creating an existent quadstore


Owlready2 on BitBucket (development repository): https://bitbucket.org/jibalamy/owlready2

Owlready2 on PyPI (Python Package Index, stable release): https://pypi.python.org/pypi/Owlready2

Documentation: http://owlready2.readthedocs.io/

Forum/Mailing list: http://owlready.8326.n8.nabble.com

Contact "Jiba" Jean-Baptiste Lamy:

<jean-baptiste.lamy *@* univ-paris13 *.* fr>
University Paris 13, Sorbonne Paris Cite
Bureau 149
74 rue Marcel Cachin