The SDMNPackage class is the outermost containing object for all SDMN elements. It defines the scope of visibility and the namespace
for all contained elements. The interchange of SDMN files will always be through one or more SDMNPackages. Specifically, an XML file
for a Shared Data Model usually would be appended with a “.sdmn” label.
This the SDMNModel sub-package contained within a SDMNModelPackage. This redefines the model association of SCEModelPackage.
This attribute contains the Diagram Interchange information contained within this SDMNPackage.
This redefines the presentation association of SCEModelPackage.