How many times have you heard that tired old question, "Is the glass half full or half empty?" Personally I don't think there is enough information in the question to formulate an intelligent answer. It would all depend on if the glass was being filled and stopped being filled at the halfway point, that would be half full, or was it completely full and was being emptied and stopped being emptied at the halfway point, that would then be half empty.
Now let us examine this a little further. (You thought it was an easy question?) :roll:
If the glass had been filled up to the halfway point and then set aside, never to have any water added, ever, then the glass is half empty. Yes it is. Because sooner or later there will be no water in the glass. It will get spilled, drank, drumped, or it will eventually evaporate. Sure... Go ahead and place it outside and hope it will rain just to prove me wrong. But it will be empty at some point in time. (What about your leaky pipe?) Now if you place it in a secure place and put a lid on it, well then you only have a half a glass of water.