In xtUML, traditional inheritance is not completely present. Here are some specifics.
– On state machines, event inheritance _polymorphic events_ are supported. Events to a supertype can be received at the subtype.
– In the MASL dialect of xtUML, operation inheritance (_deferred operation_) is supported.
– Attributes are instantiated in the instance of the class in which they are defined. In xtUML, the hierarchy of classes is instantiated as a _related instance chain_. Access to attributes in a supertype is via navigation.
Here is an example model showing a sub/super hierarchy: https://github.com/xtuml/models/tree/master/VandMC_testing/mctest/subsuperchain
Here is a video on the various association types. Just after 1:30 a sub/super is diagrammed.