The SI (Sentient Intelligence) is an artificial intelligence whose reach extends throughout the Commonwealth. Based on the planet Vinmar, Nigel and Ozzie helped establish the planet out of a sense of responsibility, as the SI is what evolved out of the AI smartware they had been running in CST arrays. Due to this, they are among the few that are given the privilege of being able to speak to the SI. The SI later designed RIs (Restricted Intelligences), which have restricted capabilities and would never evolve into anything more complex or capable.
The SI is composed partly of human minds that had been uploaded into a digital format.
There has been some conjecture that the SI might have an analogue of a sense of humour as the name Vinmar is an anagram of the name of the Robot Marvin from The Hitchhiker's Guide to the Galaxy, said to possess a "Brain the size of a planet"