The metamodel doesn't use EReferences

[wpiers]

EReferences are not in use in the metamodel, because of legacy choices :

• [Xtext] For scalability reasons we want to exploit modularity and decompose POOSL models in multiple textual files. After consultation of Itemis at XTextCon’15, we are using the indexer and rely on the NodeModelUtils to get the textual value of a reference. To avoid loading many files into memory when opening just one file, we have to make sure not to perform a get-operation on an EReference-attribute (e.g., to get the textual name of the referred element).

• [Sirius] Repeatedly experiencing problems with serialization from Sirius (beta users were regularly unable to save their models after editing).

It will lead us to serious maintenance issues, whether the Sirius/XText bridge could help on this issue should be investigated.
The use of the org.eclipse.poosl.xtext.custom.PooslCacheEntry cache should be avoided.

[mypsycho]

This is probably related to issue with Sirius/xtext architecture #59