• Definition

    ​ A field of AI that tries to emulate the judgment and behavior of a human expert in a given field. KE refers to all technical, scientific and social aspects involved in building, maintaining and using knowledge-based systems.

    knowledge-based system: a computer program that reasons and uses a knowledge base to solve complex problems.

  • Development

    | 1960s-1970s | 1980s-1990s | 1990s-2000s | 2000s-2010s | 2010s-now |
    | ————————- | ——————— | ——————— | —————— | ———————- |
    | Semantic Networks | Expert Systems | KL-One&CLASSIC | Semantic Web | Knowledge Graph |

  • Introduction

    • World Wide Web

    • Knowledge Graph

      directed graph G=

      V is a set of entities（instance: individual entities e.g. Nanjing & concept: conceptual entities e.g. City） and literals (string & datatype e.g. date, height).

      E is a set of labeled directed edges. Each labeled edge means a relation (between entities) or property (between entities and literals).

  • Application

    • Semantic Search
    • Question Answering
    • Decision Making

  • Typical KG Project

    • DBpedia
    • YAGO
    • Freebase
    • WikiData
    • OpenKG

  • Knowledge graph Techniques

    • Knowledge Representation

      知识表示

      RDF(Resource Description Framework): Triple-based Assertion Model

      (subject, predicate, object)

      RDFS: Simple vocabulary and schema. Defines small vocabulary for RDF.

    • Knowledge storage & querying

      KG Embedding: Mapping entities and relations in knowledge graphs to continues and dense low-dimensional vector spaces.

      SPARQL 查询

    • Knowledge Extraction

      K_Extra

    • Knowledge-based Question Answering e.g. WolframAlpha

    • Knowledge Reasoning e.g.Reasoning based on Rules

    • Knowledge Fusion e.g.同名不同人

    • Entity Linking