Charts are analog computers... if you point to one axis you read the solution to the equation for that point by looking at the other axis... a French Mathematician name Descartes invented the idea while staring at a ceiling it's said... that would apply to trading if you used a line chart and there was an underlying equation...
The way data is transmitted and represented is typically in time bars... it's just a convenient way to package things, that says nothing with regard to whether a chart of those convenient units can have any meaning at all... people try to give such charts meaning by adding indicators... anybody that wants to prove or disprove the usefulness of an indicator can overlay a five minute chart with hourly bars and base said indicator on the five minute bars and see how often it predicts the extreme or the close of the hourly bar, or even the direction of the close of said hourly bar. One can do that very quickly with any indicator one wants, no backtester is needed... [if anybody finds an indicator that works AT ALL, please send me a PM and don't omit the name of the indicator, the settings would be nice to have as well]
Having said all that, I'll say that I trade from charts, or rather I use charts to provide inputs to my ATS by way of lines drawn on the chart... the ATS does the trading so long as I keep drawing lines... the lines do represent what I'm thinking about the trend and strength of trend, it's the greatest man-machine interface for trading, if I stop drawing the ATS can recognize that the last line drawn is irrelevant and once it gets flat it will stay that way until I come back to the work at hand... All the chart packages that use EZ Language can read a hand drawn line and Sierracharts can do that too, I have an email in to a developer of another chart package that I like and maybe I can add his little gem of a charting package to my list of "things I really like"...
I'm a Radio Designer by trade on occasion. The equivalent thing for using the chart as a man-machine interface to an ATS is to find a beautiful looking old radio and keep it's appearance that way but replace everything in it with a modern Digital Signal Processor Synthesized tuning setup while keeping the tube audio section... I have a Heathkit SB-102 set aside for that, it's going to be very fun to put that on the air... I'd base on a Collins radio but I can't bring myself to cannibalize one of those...