Grammatical inference or Grammar Induction focuses on learning formal language rules from a series of observations of samples from the language under consideration.
If you are interested in learning some grammatical inference basics the video links below are well worth a look.
Grammatical Inference: a Tutorial
Colin de la Higuera
Also, there are several articles available through citeseer. Search on grammar inference or grammatical inference.
Finally, Amazon has several Grammatical Inference conference proceedings.