User-customized question-answering system based on knowledge graph

A question-answering system comprising:

• a user interface configured to receive a question or a reply in the form of a natural language from a user and transmit an answer or reverse question to the user, through a network;
• a natural language understanding unit configured to perform natural language analysis and question classification for the question;
• an integrated knowledge graph configured to store or manage a knowledge graph comprising multi-order relationship triples;
• a knowledge graph management unit configured to generate a context knowledge graph having entity knowledge graphs comprising first-order relationship triples extracted from the integrated knowledge graph by using a result of the natural language analysis for the question and select at least one entity knowledge graph from among the entity knowledge graphs included in the context knowledge graph by using a result of the question classification;
• a question target ranking unit configured to generate the answer or the reverse question for the question from the at least one entity knowledge graph selected above;
• and
• a user knowledge graph configured to store a user entity knowledge graph, which is an entity knowledge graph used to generate the answer to be transmitted to the user from among the at least one entity knowledge graph selected above,
• wherein, in response to two or more entity knowledge graphs being selected by the knowledge graph management unit, the question target ranking unit is configured to determine existence of the two or more entity knowledge graphs in the user entity knowledge graph stored in the selected user knowledge graph, and
• wherein, in response to none of the two or more entity knowledge graphs existing in the user entity knowledge graph stored in the selected user knowledge graph, the question target ranking unit is configured to select the two or more entity knowledge graphs as entity knowledge graphs to be ranked and generate the answer or the reverse question for the question,
• in response to at least two of the two or more entity knowledge graphs existing in the user entity knowledge graph stored in the selected user knowledge graph, the question target ranking unit is configured to select the at least two entity knowledge graphs as entity knowledge graphs to be ranked and generates the answer or the reverse question for the question, and
• in response to only one of the two or more entity knowledge graphs existing in the user entity knowledge graph stored in the selected user knowledge graph, the question target ranking unit is configured to generate the answer for the question from the one user entity knowledge graph.