Term used in analysing machine learning methods. The observation language refers to the notation used by the learning method to represent the data it uses for training. For example, in ID3, the observation language would be the notation used to represent the training instances, including attributes and their allowable values, and the way instances are described using attributes. In backprop, the observation language would be the notation used to represent the training patterns. In Aq, the observation language would again be the notation used to represent the instances, much as in ID3.
See also hypothesis language.