Illustrate classes from other standards
Most standards include some classes, codelists etc from other standards. For better understanding, it should be illustrated in the diagrams where such elements come from. On this page, two possible approaches to do this is presented.
A simple and informative way of illustrating external elements is adding a boundary around the element in the diagram, and then add a text with the name and version of the standard (the year it was published). This will give an easy and inutitive presentation.
The figure bellow shows how this was done in ISO19157:2013 - Geographic information — Data quality:
In Enterprise Architect, the boundary functionality can be found in the toolbox, under the group Common.
A downside is that the text will not be automatically changed if the name of the external standard changes.
Show complete namespace
Another and more flexible solution is to show the complete namespace for external classes, like in the figure bellow. This is will also show which package the element belongs to, not just the standard. But the text may be long and confusing, with the complete package structure.
To show full namespaces: Select Diagram and Diagram properties. From the tab Diagram, select Show Namespace and Fully Qualified Namespace.
Each one of these solutions may be applicable, but not in combination.