The first file required is a description of the domain. This consists of the classes and the types of the channels. These are usually suffixed with a ``.tdd'' (TClass Domain Description). The domain description for the Tech Support domain is shown in Figure 5.8.
Figure 5.8 says there are two classes: Happy and
Angry, and that there is a single discrete channel V, with a
range of 
.
A more complex domain description for the sign language domain is shown in Figure 5.9. In this case, there are 10 classes, and there are 8 channels. X, Y and Z correspond to the right hand's movement in space. Rotn corresponds to the roll of the hand; and Thumb, Fore, Middle and Ring correspond to measures of finger bend.
![\begin{figure}\begin{boxedverbatim}classes [ Happy Angry ] {
channel V discrete
values ''L H''
}\end{boxedverbatim}\end{figure}](img335.png)
