Natural language search engine
From Seo Wiki - Search Engine Optimization and Programming Languages
A natural language search engine is a search engine designed to search for information on the World Wide Web using techniques of Natural language processing, such as question answering. Natural language search is a major goal in the development of the semantic web.
A natural language search engine would in theory find targeted answers to user questions (as opposed to keyword search). For example, when confronted with a question of the form 'which U.S. state has the highest income tax?', conventional search engines ignore the question and instead do a search on the keywords 'state, income and tax'. Natural language search, on the other hand, attempts to use natural language processing to understand the nature of the question and then to search and return a subset of the web that contains the answer to the question. If it works, results would have a higher relevance than results from a keyword search engine.
From a commercial standpoint, advertising on the results page could also be more relevant and could have a higher revenue potential than that of keyword search engines.
List of NL search engines
- Powerset — On May 11, 2008, the company unveiled a tool for searching a fixed subset of Wikipedia using conversational phrases rather than keywords. On July 1, 2008, it was purchased by Microsoft.
- START (MIT project) 
- Search Engines at the Open Directory Project
- History of Search Engines
- Semantic Search Engine with Natural language processing capabilities