Sowa [2000] and Brachman and Levesque [2004] give an overview of knowledge representation. Davis [1990] is an accessible introduction to a wealth of knowledge representation issues in commonsense reasoning. Brachman and Levesque [1985] present many classic knowledge representation papers. See Woods [2007] for an overview of semantic networks.

Hogan et al. [2021] and Chaudhri et al. [2022] provide a comprehensive introduction to knowledge graphs.

For an overview of the philosophical and computational aspects of ontologies, see Smith [2003] and Sowa [2011].

The semantic web and its technologies are described by Berners-Lee et al. [2001], Hendler et al. [2002], Antoniou and van Harmelen [2008], and Allemang et al. [2020]. Janowicz et al. [2015] explain the role of semantics in big data. Kendall and McGuinness [2019] overview modern ontology engineering.

The description of OWL is based on OWL-2; see W3C OWL Working Group [2012], Hitzler et al. [2012], and Motik et al. [2012]. Krötzsch [2012] describes the OWL 2 profiles. Baader et al. [2007] overview description logic.

Heath and Bizer [2011] overview the vision of linked data. DBpedia [Auer et al., 2007], YAGO [Suchanek et al., 2007; Hoffart et al., 2013; Mahdisoltani et al., 2015], Wikidata [Vrandečić and Krötzsch, 2014] (http://www.wikidata.org/), and Knowledge Vault [Gabrilovich et al., 2014] are large knowledge bases that use triples and ontologies to represent facts about millions of entities.

The top-level ontology is based on BFO, the Basic Formal Ontology 2.0, described by Smith [2015] and Arp et al. [2015] and the ontology of Sowa [2000]. Other top-level ontologies include DOLCE [Gangemi et al., 2003], Cyc [Panton et al., 2006], and SUMO [Niles and Pease, 2001; Pease, 2011]. A more lightweight and widely used ontology is at http://schema.org.

SNOMED Clinical Terms (SNOMED CT) [IHTSDO, 2016] is a large medical ontology that is used in clinical practice. You can explore it at http://browser.ihtsdotools.org/.