Perhaps I should add one of the most important aspects of play on the half-open file.
What do you do when the opponent has a healthy Pawn (instead of a backward Pawn) on the half-open file? Consider the following Pawn formation:
Black's Pawn at d6 is healthy, guarded by his c7-Pawn. If White were to double Rooks in a futile attempt to pressure the d-Pawn down the file, not only the reader but the Pawn itself would deride him. So is there no way to increase the pressure on Black?
Yes, there is a way. White should play Nd5, planting an active Knight on the outpost d5-square. Black now has the choice of either allowing the Knight to dominate the position from that strong central outpost, or playing c7-c6 to drive the Knight out... and this weakens the d-Pawn, leaving it backward and vulnerable on White's half-open file.
Often, occupying a semi-open file promises even more advantages than was the case with an open file. Unlike in the case of an open file, an opposing pawn is present on a semi-open file. This pawn is then frequently reduced to being an object of attack for our major pieces. The pressure exerted against a backward pawn can either lead to the win of the pawn or it can force your opponent into passive defense. Then you can look for other objects to attack in order to overload your opponent's defensive resources.
The second advantage of the semi-open file is that your opponent cannot organize his rooks in order to initiate an exchange of rooks. We do not open this file until the moment comes when it is to our advantage; for example, when we have already doubled our major pieces on the semi-open file. One of the typical plans is to advance our pawns in order to force the exchange of the pawn which is under attack, thereby opening the file.