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Knowledge Graph

  • What is a Knowledge Graph?
    • In Logic Programming, KG is logically consistent collection of facts
    • In
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Data Integration + Concepts AND Relationships are first class citizens = Linked Data and Metadata encoded in a Graph
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Ontology + Instance Data = Knowledge Graph
  • Glossary
    • Taxonomy
      • Taxonomy is hierarchical
      • Multi-lingual taxonomy is used for searching data in English within documents that are in non-English
    • Ontology
  • What is in a Knowledge Graph?
    • A semantic graph database (scalable, secure, acid)
    • Ontologies and taxonomies
    • Reasoning and rule based processing
    • Smart integration of silos of information
    • Machine Learning and Advanced Analytics
    • Natural Language Processing and Text classification
  • Types of KG
    • Document/text based KG
    • Entity/Event bsaed KG
  • Representations of KG
    • Symbolic representation - s,p,o (triplet), p (s,o), (s,p,o)
      • s = subject, p = predicate, o = object
      • used in logical inference systems, DB and DB integration systems
    • Vector representation - s,p,o ε
      • used in NLP
  • Methodologies
    • Creata Data/Execute Queries
      • there are 2 approaches: Materialization (ETL) and Virtualization (No ETL)
      • Materialization: Create an ETL job to extract the source data from RDBMS, apply the mapping defined, then transform and load it to a graph DB.
      • Virtualization: Take SPARQL queries as input, apply the mapping logic and convert it into a SQL to extract the data. The results are then stored in a graph DB.
  • Tools
    • Data modelling: RDF, RDFS, OWL?
    • Query language: SPARQL
    • Ontologies
      • schema.org - universal graph labels, 31% of the internet uses this
      • Good Relations, FIBO, Gist
      • VOWL: Visual Notation for OWL Ontologies
      • WebVOWL - Web-based visualization of Ontologies
      • Protégé - Free, open-source Ontology editor - has VOWL plugin
    • Mapping from RDBMS to RDF graphs: R2RML
    • Visualization - Grafo
  • Examples of public data sources using KG
    • Wikidata
    • Datacommons.org - Knowledge browser,
    • Library of Congress
    • data.gov
    • census.gov
    • NOAA
    • The Linked Open Data Cloud
    • data.world - is a cloud-native enterprise data catalog, with data virtualization/federation, build on Knowledge Graph

References