Unsupervised grammar inference systems for natural language

In recent years there have been significant advances in the field of Unsupervised Grammar Inference (UGI) for Natural Languages such as English or Dutch. This paper presents a broad range of UGI implementations, where we can begin to see how the theory has been put to practise. Several mature systems are emerging, built using complex models and capable of deriving natural language grammatical phenomena. The range of systems is classified into: models based on Categorical Grammar (GraSp, CLL, EMILE); Memory Based Learning Models (FAMBL, RISE); Evolutionary computing models (ILM, LAgts); and string-pattern searches (ABL, GB). An objectively measurable statistical comparison of performances of the systems reviewed is not yet feasible. However, their merits and shortfalls are discussed, as well as a look at what the future has in store for UGI.