I would guess that they used a very declarative style of Lisp programming, where much of the code looks like a specification. Here they used Common Lisp enhance

I would guess that they used a very declarative style of Lisp programming, where much of the code looks like a specification. Here they used Common Lisp enhanced with a relational programming model, like an in-core database with an embedded query language. The developer(s) were probably quite experienced with it.