1. A computer-implemented question-answering method, comprising: receiving an input question; determining multiple types of knowledge databases available for searching, wherein the multiple types of knowledge databases provide data in different formats and include a question-answer paired knowledge database, a plain text knowledge database, a resource description framework (RDF) knowledge database or a combination thereof; when the question-answer paired knowledge database is available, searching question-answer paired data from the question-answer paired knowledge database to determine a first candidate answer to the input question; when the plain text knowledge database is available, searching plain text data from the plain text knowledge database to determine a second candidate answer to the input question; when the resource description framework (RDF) knowledge database is available, searching RDF data from the RDF knowledge database to determine a third candidate answer to the input question; and evaluating the first, second or third candidate answer to generate a final answer to the input question.