A very quick introduction to UML Activities and Actions. Please note that SysML® introduces many useful additions to Activity modelling as covered later in the main SysML trail.
This trail section is currently mostly just annotated diagrams only - with no additional text explanations except for linked Notes and Snippet spec extracts
This tutorial trail section includes some simulation example micro-videos
If you are already a "UML ninja" by all means skip to the SysML starting point:
You may also like to view these related tutorial trails and videos: