In order to tell the learner what the class of each file is, a class label file (usually ending with ``.tsl'' for training data and ``.ttl'' for testing data; although this can be modified at the command line) is also provided. The format for this file is simple, and an example is shown in Figure 5.12. Each line consists of a filename (relative to the current directory, or alternatively, given as an absolute path), followed by a space and then the class label. The class label must be one of the classes listed in the domain description file.
