Comment by kragen

I don't think you need Lisp macros for it; you could use just a regular Lisp function. I don't think the standard R5RS macros are powerful enough to grovel over the query expression to make a list of the free variables, but then, standard Scheme also doesn't have records. I think Guile has a procedural macro system that you could use, but I don't think it would be a good idea.

Yes, I think the semantic divergence is more fundamental. Triple stores and graph databases and binary relations are awesome, but they aren't what Datalog is.