I am designing an UML diagram for an Apple Watch Extension. How should I represent host app using UML ? UML Node or UML component ? Please note that there can be inter app communication between the extension app and the iPhone app (host app).
UML nodes are apparently used to depict physical resources, so your watch would be a node, whereas a component is usually understood as a software component. Since you want to model software, go with components (which will also nicely visualise the plugging between extension and host).