The Mechanics of Gremlin OLAP

A Gremlin traversal is an abstract description of a legal path through a graph. It involves the creation and branching of traversers, which are pointers that move through the graph according to instructions dictated by the traversal. Traversers can die along the way due to filtering or walking down dead-end subgraphs. The surviving traversers provide answers based on their lineage across the graph. Gremlin OLAP is a distributed computing model for executing Gremlin traversals against any TinkerPop-enabled graph system, using a message passing algorithm. It involves vertex programs that are evaluated at each vertex in parallel and a master traversal that coordinates the computation. Some steps require aggregation at the master traversal, while others involve reducing barriers to yield an aggregate of their reduced associative/commutative form. The TraversalVertexProgram drives the evaluation of distributed traversals, with the complexity of the computation residing in both the vendor's GraphComputer implementation and Apache TinkerPop's Traversal implementation.