Get a good book. I recommend the speech and language processing of Yurafsky and Martin. Learn Java, or better, Python and one or more of the toolkits for NLP.
If you want Prolog, try Prolog and Natural Language Analysis , but understand that a logic-oriented approach has almost completely gone out of fashion in the last two decades because it has proved to be too fragile and too expensive. Statistical methods and machine learning are all now, and approaches that combine logic and statistics are truly advanced research.
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