I think the man will be turning in his grave at this thread. If you want to use classical culiniary terms then you must respect what they mean. you cannot make demi-glace unless you reduce sauce Espangnol by half, demi means half. you can call it anything else and often I would agree it tastes better but if you call it demi-glace thats what it is. In nouvelle cuisine jus lie is a term often used this means thickend juices a good substitute for demi-glace if made well.
I shall be back on this one but must dash to cook dinner.
steve
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