set in layout block

[Noeck]

Hi,

how can I put a set command in the layout block?
I am asking for the following beamExceptions and in general:

----------------
\version "2.18.2"
% within the notes:
{
      \set Timing.beamExceptions = #'()
      a8 b a b
}

% in layout block:
{
      a8 b a b
}

\layout{
  \context{
    \Staff
      beamExceptions = #'()
  }
}
----------------

Is that correct?
It seems to work but where has the ‘Timing’ gone?
How does it know about the Timing?
Is that a general rule, that \set commands have no dot-syntax in the \layout
block but only work with \context { \‘Context’ … } ?

TIA,
Joram