"If you don't like the weather [forecasts]..."

Written by Chuck McCallum Friday, 04 February 2011 15:31

"... just wait a few minutes." By now I've lost track of whether today's blizzard is tomorrow's arriving early, or yesterday's arriving late, but with Needle's record of the last four days' weather forecasts from noaa.gov, I can see which way the forecasts have been trending, even if there's still no telling what will actually happen.  (Read on to learn how I did it.)

This database also shows how Needle can accumulate data over time from a website whose contents are changing.  The idea is that the date of collection itself is something you explicitly model, and that date is used to distinguish other nodes. In this database's model, the central type is a Forecast, which allows any number of Predictions for the coming days, but has precisely one Location and one Date (note the two unchecked "multiple" checkboxes).  That means that Needle will never automatically merge Forecasts made on different dates or for different Locations.  The other important checkbox for this domain was in the source settings for noaa.gov: I changed Needle's collection mode from the default, "Collect and replace", to the setting I needed, "Collect and add." Voilà! Neatly organized historical weather prediction data, accumulating over time into my online database.