So basically, it is a triple-store with keeps track of time and no mutation of past.
They have their own query language but it looks to me that they did a great job at making it as close to SPARQL as possible, which personally I am familiar with.
It is important to understand that datalog is not a new query language. It is an old one, with a strong pedigree. It has power equivalent to the relational model plus recursion.
SPARQL is cool, and they did a good job making it look a little like datalog.
SPARQl1.0 is equivalent to a datalog without recursion. Wonder what SPARQL 1.1. with property paths is equivalent too. Any way a hobby project idea I won't have time for is implement the datomic api on top of a systap bigdata quad store.
They have their own query language but it looks to me that they did a great job at making it as close to SPARQL as possible, which personally I am familiar with.
Pretty neat stuff.