I'm curious what sort of domain specific languages (DSLs) are used in GIS. The only one I can think of is the DOCELL language that was provided in ArcInfo Workstation GRID, but is no longer supported.
FME's workbench would classify as a graphical DSL, and its generated/editable scripts as a DSL
ArcGIS's Model Builder could also be described as a graphical DSL.
SLD is described as an encoding, but may also fall under the category of an DSL.