I really like the declarative style of make, to the extent that I've been abusing it as an automation tool. Doing things like checking if a server is alive or setting up a serial port. But due to limitations like depending on mtime and issues with special characters in targets, I've switched some of my more intensive Makefiles to prolog using this: https://github.com/webstrand/robo.

When I find the time I hope to write bindings for netlink for prolog, so that I can declaratively create and configure network namespaces. Complete declarative system configuration using prolog would be a dream come true.