The guys behind GT.M (a system I’ve covered on rare occasions) have published and tried to popularize a paper describing the usage of MUMPS Global Persistent Variables
 to model and store the different types of NoSQL databases: key-value stores, columnar stores, document databases, and graph databases.
According to the paper, available ☞ here and embedded below, both GT.M and InterSystems Caché have been using this technology for quite a while.
Any thoughts about this paper?
Original title and link: Paper: A Universal NoSQL Engine Using MUMPS Global Persistent Variables (NoSQL databases © myNoSQL)