The Foundry Ontology is a powerful tool and one of THE selling points of the whole Platform. A lot of capabilities are developed that require the addition of separate Ontologies or facilitate those. This is great to share governance by assigning ontologies to different domains.
The main restriction or tradeoff that comes with this is that you cannot define Link Types between objects from different ontologies. Therefore, I suggest to add another LinkType category called “External LinkType”. This external link type could link to other ontologies and maybe even outside the platform and would be the basis to scale and orchestrate ontologies within Foundry but also connect them to other things.
From a technical perspective, I can imagine that link types are currently within ontologies because they need to be indexed. Keeping this separate category can come with limitations (performance / flexibility / availability) which one would deliberately accept. However, the benefits overweight in my opinion since things like master data systems / ontologies or common knowledge bases could be easily integrated into the different world views (ontologies) of respective domains.
My motivation regarding this primarily comes from the semantic web technologies where a relation is defined by referring to an IRI which is globally unique and also valid as a reference to things outside of the actually ontology (e.g. in OWL language or SKOS).
I think this would greatly enhance the semantic aspects of the ontology, since links for object types or properties to commonly accepted ontological terms would be possible and create transparency for understanding the data beyond simple descriptions or groupings.
Another key characteristic of an external link is that it is one-sided and that the target does not necessarily need to know about the link type it is referred in. This is also exactly the case in the semantic web.
Cross Ontology linking would be a great addition, and would allow the splitting of massive organisation wide ontologies into smaller ones, which are easier to manage, group and develop in, while sharing some ‘core’ objects that link across and between them, without each ontology creating their own versions thereof.
It would hopefully also resolve the issue in the ontology editor where you have to keep updating and refreshing the page to save changes, as in parallel someone else somewhere has made a change, and now your state is out of sync.
Similar to vertex graphs defined by functions, you could link the external Type to a type declaration / interface
You have the freedom to call external sources
You could define the filtering rules to object types from other ontologies.
Hence, the returned data by that function would actually refer to an object type which is not directly searchable but only accessible through the defined link. The schema due to the interface would appear in the ontology manager though.
And what would be even more useful is a repository of schemas / ontologies commonly used in industries / use cases. Someone has to be the author/owner of these and any dependencies made to them would have to be versioned.
If you could create common semantics it would also allow more reuse across solution development.