"Long term", "medium term" and "short term" are all defined by the individual. Personally, I don't subscribe to the "medium term". You have a trade that is entered and exited in a short time period, if the trade is kept open for longer than a "short" time then it is a "longer" trade.
As the code behind the expert is based on numbers of bar, the comments have to be referenced against the periodicity of the bar. You can apply the same expert advisor to a one-minute realtime chart, a daily chart, weekly chart etc and the comments will all be referenced to the most recent 21 bars, representing 21 minutes, 21 days or 21 weeks etc. The timeframe of the trades is dependent on the timeframe of the "advice"
Hope this helps.
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