ODM12 — Serializing a self-contained model is problematic

Because of the composition relationships in the current RDF and OWL metamodels, it is not possible to create a model that:

1. contains an instance of class Namespace, and
2. has an XMI serialization with a single root element that owns, directly or indirectly, all the other elements in the model.

Class NamedGraph is the only class that can own Namespace (that is, the association between NamedGraph and Namespace is the only composite association involving Namespace). Therefore, a model with an instance of Namespace must either be serialized with a root element of Namespace or NamedGraph. In either case, the serialization cannot contain a Source or a NamespaceDefinition. No associations in the metamodel allow a Namespace or a NamedGraph to own a Source or a NamespaceDefinition, either directly or indirectly.

Conversely, a model with a Source has no serialization in which the Source can own, directly or indirectly, a Namespace.

The serialization of an ontology represented using the metamodel must contain (at least) two instances of metamodel classes. This is problematic for ECore, where the persistent representation of an ontology must exist in multiple files.