Hi
I think that the intention was just to be able to use whatever short
name suits you.
You could use:
@prefix prj: <http://usefulinc.com/ns/doap#>
@prefix l2: <http://lv2plug.in/ns/lv2core#>
@prefix lv2: <http://myownsite.org/LowVoltageVariation#>
...
I am not judging.
Regards
Bruno