What signs to use in specific domains is problematic. For example, the addition sign, the ‘plus’ sign originated in the number domain, the arithmetic domain. If you are going to use numerals as signs, the appropriate signs that indicate ‘operations’ are the familiar ones: + – X and ‘divide’ which is generally not easily accessed in a normal font set, as in this case.
The issue is that if at the moment we are in the ROD MARK MAKING DOMAIN and manipulating real rods in order to see things which we then want to ‘write down’, should we have for example a special sign which means, ‘put the rods end to end’? It would be easy to say ‘What’s the problem, just go ahead and use the normal signs.’ I have done this, and to be honest I am not sure that this is a bad idea. It seems easy and obvious, mainly because people in general including teachers don’t know of any other domain-specific signs. (THESE DO EXIST HOWEVER)
It can certainly be construed as being ambiguous, particularly by some modern rod proponents and almost undoubtedly philosophers of maths. They say that DOMAINS should keep their MARKS specific and separate. What to do, what to do?
More of this later…