Customizing the SysML profile (SysML)
You can extend the properties and linking capabilities of Requirements and other SysML items through Tag Definitions.
For more information about using Tag Definitions to extend properties and linking capabilities, click here 
You can create your own aliases for the diagrams, items and links that appear in the SysML profile.
For more information about creating aliases, click here .
.You can create new item and link types that are based on SysML item and link types through lightweight extensions. Through lightweight extensions, new item and link types are created as subtypes of SysML item and links types, and as such they inherit the properties and linking capabilities of the SysML item and link types they extend. In addition, the new item and link types appear in the same selection dialogs as the item and link types they extend.
For more information about lightweight extensions, click here