It should be mentioned that when a signal is dark, it would still have an
aspect, like stop or clear, it just would not be lighting the output. This
is needed because other signals next to it would base their aspects on the
aspect of this signal. If the concept of signal logic is integrated inside
the signal, it being dark should hide what state it would show should it
become lit.
Held is kind of different, while it isn't really an aspect, it causes a
specific aspect regardless of the signal logic. Typical case is stop (or
danger) even when the logic would otherwise has computed clear.
I think this is why Bob J was pointing out that simply knowing the
appearance (displayed aspect) does not let you know about these other
features. So depending on what is known or not about the signal determines
if you can accurately represent it externally to that signal. Granted for
some people, it will need the extra details to be considered right. Others
will not require that high of an accuracy about the signal. I think this
ambiguity is part of why JMRI doesn't do some things others might consider
simple.
-Ken Cameron, Member JMRI Dev Team
www.jmri.org
www.fingerlakeslivesteamers.org
www.cnymod.org
www.syracusemodelrr.org
Ken Cameron