[vilya]

There's also Orc: http://orc.csres.utexas.edu/

Regarding "not taking off": this model is actually very common in the vfx industry. Most high-end content creation tools (Nuke, Maya, Houdini, etc) have a node graph which you assemble in the tool, where the nodes define processing operations & are usually plugins written in c++ or something like it. It's not a language per-se and the semantics are tightly bound to the individual tools rather than being independently specified, but the underlying idea is the same.