Currently there is very little information available online on GQL, the SIGMOID paper 'Graph Pattern Matching in GQL and SQL/PGQ' linked in the article is a great intro to the topic [1]. The authoritative source is the ISO spec [2] but it is paywalled. In short, GQL ISO is inspired by the following query languages and has the aim to standardize graph querying:

- SPARQL: A query language for RDF data, developed for semantic web by W3C. [3]

- PGQL: Property Graph Query Language developed by Oracle [4]

- Cypher: Neo4j's query language designed for its graph database. [5]

- openCypher: An open-source initiative to make the Cypher available beyond Neo4j database. [6]

- GSQL: TigerGraph's graph query language, SQL-like syntax for graph querying. [7]

- SQL/ PGQ: Another subproject of the SQL standard group introducing graph queries inside SELECT statements. Superseded by GQL (chapter SQL/PGQ Property Graph Query in [8])

[1] https://arxiv.org/abs/2112.06217

[2] https://www.iso.org/standard/76120.html

[3] https://www.w3.org/TR/2013/REC-sparql11-overview-20130321/

[4] https://pgql-lang.org/

[5] https://neo4j.com/docs/cypher-manual/current/introduction/

[6] https://opencypher.org/

[7] https://www.tigergraph.com/gsql/

[8] https://en.m.wikipedia.org/wiki/Graph_Query_Language