Tags and keywords
For reference, the associated policy note (you don't need to visit it yet):
Note that this policy does not state that Associations MUST use Strings as keys in all Associations, just that where Strings are indeed used they SHOULD be encapsulated as '$k$' String variables.
The '$k$' convention has standalone use, and it is also used in combination with other conventions. For examples, as we'll see in later slides, the Webel help Rule system used to register '$opt$' (options) and '$arg$' (arguments) help holders with the HelpF` and HelpO` help registries uses the '$k$' key convention.