LIFER/LADDER was one of the first database natural language processing systems. It was designed as a natural language interface to a database of information about US Navy ships. This system, as described in a paper by Hendrix (1978), used a semantic grammar to parse questions and query a distributed database. It was implemented in Interlisp.
The LIFER/LADDER system could only support simple one-table queries or multiple table queries with easy join conditions.
Some examples of queries it could accept:
What are the length, width, and draft of the Kitty Hawk?
When will Reeves achieve readiness rating C2?
What is the nearest ship to Naples with a doctor on board?
What ships are carrying cargo for the United States?
Where are they going?
Print the American cruisers’ current positions and states of readiness?
References
↑Manaris, Bill Z. (1994). "AN ENGINEERING ENVIRONMENT FOR NATURAL LANGUAGE INTERFACES TO INTERACTIVE COMPUTER SYSTEMS". International Journal on Artificial Intelligence Tools. 03 (04): 557–579. doi:10.1142/S0218213094000303. ISSN0218-2130.