[r-t] Lead-based methods [was: Poll on consecutive blows in the same position]

[Don Morrison]

On Mon, Dec 29, 2014 at 6:29 AM, Graham John <graham at changeringing.co.uk> wrote:
> Methods made up of an unvarying sequence of changes i.e. statically
> defined by a sequence of place notation.
>
> and...
>
> Methods where the changes are determined by rules based upon the
> position of bells in the previous row(s) i.e. dynamically defined or
> Dixonoids.

Note, however, that this does not exhaust the possibilities for rule
based method. While "position of bells in the previous row" is
sufficient for Dixon's, and might even be a suitable definition for
the undefined term "Dixonoid" (possibly extended to multiple preceding
rows, as Graham implies), there are other possibilities. I doubt that
we are clever enough to enumerate all the things someone might in the
future imagine. Here are a couple of the possibilities:

- the rule might depend upon the number of changes rung since a particular
change was executed; note that this is +not+ the same as a static sequence
of changes, since in a rule based method there's no guarantee that the
intervening changes will always be the same

- the rule might depend upon some random process (yes, this is pretty
bizarre, but to some of our, in some cases still living, ancestors
multi-extent blocks and singles in surprise seemed pretty bizarre --
we cannot allow our limited vision to restrict what others might
choose to do in the future; and it's arguably only one step removed
from the random, static methods Philip Earis was seriously considering
ringing a few years ago).

- the rule might depend upon the position in the future of some bell,
if we +don't+ make a varying change (this may be the same as depending
upon positions in the past, since they may determine the future, but
I'm not certain, in the face of other kinds of rules?)

- the rule might depend upon the sum total of what has been rung in
the past: for example, maybe an MEB the first "extent" of which is
incomplete, and the last extent of which gets extra rows added in some
cleveer way to complete it: again, this may degenerate into just
depending upon the positions of bells in past rows, but I'm not sure

- Dixon's and similar methods operate by having a basic process that
keeps going, the "rules" part mostly being variations on that process,
but that only affect a single change. The variation might instead be a
shift of the underlying, basic process. Again, this may degenerate
into depending just upon arbitrarility many preceeding rows, but I'm
not sure that with interacting rules that is necessarily the same.

Are many of these weirdo things likely to be rung? No. But if we're
trying to accomodate things not yet dreamt of, we do need to be
careful not to preclude something sensible we're just not clever
enough to imagine ourselves at the present time.



-- 
Don Morrison <dfm at ringing.org>
"A civilized society is one which tolerates eccentricity to the
point of doubtful sanity."
     -- Robert Frost, quoted in _The New Republic_ 25 October 1958