Suppose I have a feature "Pool Size" whose levels are: Big, Medium, Small.
Surely if a house doesn't have a pool it certainly won't have a value for "Pool Size".
Q1-For this particular instance/house, should I consider the value for "Pool Size" missing ('NA') or should I makeup a new category for 'Pool Size' dedicated to houses that do not have a pool size lets call it 'None' or 'NoSize'?
Q2-If I choose to makeup a new category for 'Pool Size' then my feature would become categorical instead of ordinal. Wouldn't that be a problem as I am essentially changing the nature of the variable?