# Limitations

## Current limits

The following limitions currently apply to Owlready (but may be fixed in future version):

> - Owlready supports only OWL/XML file format.
> - Owlready loads ontology in memory (might be problematic for very big ontologies).
> - Owlready associates each entity to a single ontology when saving OWL files, while OWL allows to spread the various facts and assertions in several ontologies.
> - Owlready does not take into account subproperties when obtaining the values of a property (unless using get_relation()).
> - Owlready does not support ‘punning’, and the same name should not be used for two distinct entities, even if their types differ (e.g. a class and a property).
> - Instance edition is still experimental (especially the HTML support).