Is it juvenile play or could be aggression

Question
I have three dogs, my newest member a rotty, 1 year 6 months, not rescued as such but needed rehoming due to personal circumstances of last owner.  She is a lovelly girl, bows down to my alpha male but would like to know how to stop her bounding at other dogs.  She wants to play, but sometimes too hard.  My other dogs are large so they do not have a problem with it, but, as you can imagine the breed sends thrills of fear down people due to the press.  How do I control the bounding?  If I call she comes sraight back,but it is that initial run that I need help with.  I don't want to put her on the lead everytime a dog comes near as I feel that would give her an inability to flee so would only leave fight.  I certainly do not want her to become aggressive.  Have had one aggressive dog that I have managed to calm, and is a good guy.  It's just you now how people see the breed before the dog. Any help would be more than welcome.

Answer
This dog will not learn to perceive other approaching dogs as a threat so long as you do not communicate anxiety down the leash.  She needs to be contained on long training leash so her first instinct (to approach other dogs with high hilarity, not threatening the dogs but alarming the owners) can be redirected.  This will work well once she has been introduced to it: as she approaches another dog, if her body language is such that you are concerned, go immediately in the opposite direction, your dog will not have any choice but to follow you.  Then turn and ask her for a trained behavior, then approach the play partner again.  Your dog should have calmed sufficiently so that she will not be hilariously approaching the other dog, but if she has not, repeat the exercise.  It's highly unlikely that any other dog will immediately respond with a threatening demeanor because your dog has changed direction.  I assume that you are discussing dog park interaction?  Dogs that are on long lead are not in a position to choose fight or flight; they are free to flee (because the lead is long); you would readily be able to perceive intent from a dog aggressive dog in any dog park.  If I misunderstood your question, please repost.