www.inference.phy.cam.ac.uk/dasher/

                                                                    Dasher
                                                              by Kim Mason

                                                            What is Dasher?
Dasher is an information-efficient text-entry interface, driven by natural continuous pointing gestures.  Dasher is used when a key board cannot be used to enter text.  This software allows a person to write text using one hand.  This can be done by, joystick, touchscreen, trackball, or mouse.  It can also be used in any language. 
                           
                                                     Dasher and special needs
Dasher allows the user who is unable to use a standard keyboard, the opportunity to create text easily and quickly (up to 39 words a minute).  The one ability that is required of its users is sight. 

                                                       How does Dasher work?
Dasher is referred to as a zooming interface.  You simply point where you want to go.  Where the user zooms in on, they will recognize that their field is painted with letters, so as you point your zoom onto letters that correspond to the piece of text that you are writing, words will be created.   The interface uses predictive letters to help the user create word quickly.  Pieces of the word (puzzle) fall into a predictive language model that we use every day. 

                                                          Information on Dasher
By moving your mouse you are able to write a sentence.  Dasher is writing through navigation.  The user navigates through a library of books.  The important part is that you realize you are navigating on a one demensional shelf, where the user recognizes the letters alphabetically arranged from a - z.   To start we navigate into the library where we pick our initial first letter (example “h”).  Within the “h” library we can see all the books from “ha” - “hz” in alphabetical order again.  However, now you will start to notice that “ha,” “he” and “ho” are farther out on the screen because they are the letters that will most probably occur next.  Important to note all other letters are there, example “hk,” “hq” and so on, they are smaller because that sequence of numbers is improbable. It is likely you will not want to use these letters.  Let’s go back, if we picked “he” and we want to write “hello,” than we will continue on to pick up the “llo.”  White spaces are used for spaces in the text that is being written. 

                                                                     How do we?
First of all lets look at it like driving.  When we want to go left, we steer left, when we go right, we steer right.  If you want to go up, you point up and if you want to go down you point down.  This is what the user is doing with his/her mouse in order the letter combinations that are needed.  The distance the user is from the center of the screen is determining the speed in which the letters appear.  If the user needs to erase what has been written, the user than points to the left, undoing the text that was recently written. 

★    Important to remember, text does not need to involve clicking of the keyboard, text can be written using Dasher. 

       This is a wonderful software for individuals with extreme limited mobilities.

Reference
    www.inference.phy.cam.ac.uk/dasher/