If we are told to hold 250 knots and our route takes us to the arrival, should we slow if there is a 190 speed published in the arrival at (Wojic)?? on the arrival (Patts into PHL)?? Do we maintain 250, or automatically reduce to the published speed?? For what it's worth, we have never been taken off the arrival. I realize we were issued a speed, but does the arrival speed mean to slow down? I also realize ATC instructions take priority, but for example we are given "transition to 300 kts". When we hit 10,000 feet we are slowed to 250 regardless of the 300 instruction. Thoughts?