Gremlin (query language)

Gremlin is a graph traversal language and virtual machine developed by Apache TinkerPop, a project of the Apache Software Foundation. It works both for OLTP graph databases and for OLAP graph processors. Its automata and functional foundation lets it support imperative and declarative querying, user-defined domain specific languages, an extensible compiler and optimizer, and single-machine or multi-machine execution, and it is Turing complete. Wikipedia offers an analogy: TinkerPop and Gremlin are to graph databases what JDBC and SQL are to relational databases, and the Gremlin traversal machine is to graph computing what the Java virtual machine is to general purpose computing. A traversal is compiled to a sequence of steps, an instruction set of about thirty steps, and because the fluent style needs only function composition and nesting it can be hosted in many languages, which is why dialects such as Gremlin-Groovy, Gremlin-Java8 and Gremlin-Scala exist. The project began in October 2009, released v0.1 in December 2009, became an Apache Incubator project in 2015 and a top-level Apache project in 2016. Gremlin is Apache 2 licensed and open to graph system vendors.