Are stock charts of different time scales (1min, 10min, 1h, 2h, etc) usually generated from a default/base scale (say 1m) stored by the vendor? I mean, when I ask for a 5min chart for GE on Yahoo, are the 5-min prices derived from a 1min series or there exists a 5min series in the database? How do these data vendors store the myriad data of different time scales?