====== Speech recognition and voice commands II – grammar based recognition ======
In grammar-based recognition, to make the robot recognize your voice commands we need to specify the set of possible commands.
Most of the commands will share some parts, like for instance: //run forward with maximum speed// and //run backward with maximum speed//.
It sounds inefficient to enumerate each command separately, as there will be a lot of redundant stuff in such configuration file.

That is why, instead of explicitly write every possible commands, we define a grammar file, which allows us to do the same in a more compact way:

<code>
#JSGF V1.0;

grammar robot;

<forward>  = run forward;
<backward>  = run backward;
<stop> = stop;
<max>  = (<forward> | <backward> ) with maximum speed;

public <item> = <forward> | <stop> | <backward> | <max> ;
</code>

===== Exercises =====
  - Update your project. To see how, go to: [[did:roboclub:github_tutorials:updating|Pulling/updating]]
  - Play with **speakBack** method :)
  - Define new command(s) that will allow to specify speed of robot, for instance: //run forward with speed 50//
  - Do the same with a rotation angle, for instance //rotate motor A 4 times forward with speed 50//.
    - Think of how to allow different versions of this command, such as:
      - //rotate motor A and B 4 times forward with speed <some value>//
      - //rotate motor A and B and C 4 times forward with speed <some value>//
      - Read JSGF manual to see how to do this (section [[https://www.w3.org/TR/jsgf/#14660|Unary Operators]])
    - How to keep some information about the context? How to implement a short-term memory of a robot?Add following voice commands: 
      - //Increase/Decrease speed by <some value>// or //Slow down/speed up//