From the blog post:
The Neo4J team recently blogged about a graph query language called Cypher, and reading their post got me motivated to write about something I’ve been working on for a while. Plasma is a graph query engine written in Clojure. Currently it sits on top of the Jiraph graph database that was written by Justin Balthrop and Lance Bradley for a geneology website, Geni. (It would be less than a days work to get it running on top of another graph database though.) The query engine is built using a library of query operators that are combined to form dataflow graphs, and it uses Zach Tellman’s asynchronous events library, Lamina, to provide concurrent, non-blocking execution of queries.