Are all commands mandatory

Are all implementations expected to support all commands? It seems like
there are some for which this is not possible e.g. on a mobile device
changing the window size might not be possible. On the other hand it
feels like supporting navigation ought to be mandatory. This sort of
suggests that the commands can be divided up into ones that a browser
SHOULD supprt, if it can, and ones that it MUST support. Does that seem
sensible? If so, which are in which category?

Received on Thursday, 12 February 2015 23:27:19 UTC