Tags and keywords
The following additional Block-based stereotypes, described in the spec as "user-defined" and available in the MD SysML Plugin and Cameo Systems Modeler® tools prove useful on real projects:
SysML: The «system», «subsystem», «external», «domain» and «system context» keywords are for "user defined" block Stereotypes (they are not part of core SysML); they are supported in MagicDraw/Cameo as Non-Normative Extensions.
A typical (but not only) use is for Blocks that type Properties in an Internal Block Diagram (IBD) used as a so-called "system context diagram". See linked slides below for examples of some possible uses of these Block extension (then make sure you come back to this trail of course).