[r-t] Practical Extension
robin at robinw.org.uk
Fri Aug 3 11:31:19 UTC 2018
Following on from pervsious correspondence:
Richard Grimmett asked "Are you saying there is much less significant
improvement to be made on what was there already than previously thought?"
Isn't this inevitably true from all human endeavour? As an example I met
only today, when I'm going on a week's ringing holiday, I like to get
the OS maps for the area which also come with a free mobile-phone
version. About three month ago, my usual supplier had changed their
web-site which made it very difficult to select the maps I wanted so I
changed supplier. Today I find the original supplier has gone bust 'due
to some very recent & unforeseen setbacks following the relaunch of our
website'. Not much improvement there, then.
As regards Extension, I've been interested in it for at least 25 years
so it is comparatively easy for me to do extensions by hand. It is,
after all, a practical subject. (Thought: if you can't do it by hand,
how the ... can you write a program to do it?)
Everyone on this list should be capable of doing it. If you understand
place notation, then I could teach any of you to do it within an hour -
face to face, of course.
One point - I think it is a bit of a delusion to hope that every method
can be extended to every succeeding stage. We should be quite happy with
a particular method not having extensions at all. There is no
fundamental theorem saying there must be extensions within any given
rule-space. (Why does the name Godel spring to my mind here?).
The current rules on extension have one advantage. They are objective
and make no value-decision on any one in a set of competing extensions.
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