I want to draw a class diagram that shows the following for an application:

* An external content management system that publishes some news items.
* The class that represents the news item in my application.

The question is shall I include the external content management system as a class in my diagram (and maybe give it a different color or add a comment that it is an external component) ?

if the answer is no, what shall I include in the class diagram ? the news item class only ? and how to show the relation between the news item class and the external content management system ?