The next step is _Extended_ regular expressions that characterise Regular Relations (RR) and that specify Finite Strate Transducers (FSTs). See: http://users.i

The next step is _Extended_ regular expressions that characterise Regular Relations (RR) and that specify Finite Strate Transducers (FSTs). See: http://users.itk.ppke.hu/~sikbo/nytech/gyak/05_morfo/xfst/book.pdf_1.pdf http://users.itk.ppke.hu/~sikbo/nytech/gyak/05_morfo/xfst/bo... Advances: - symmetry input:output (reversable) - readable/maintainable expressions due to _naming_ of sub-expression Implementations: - Xerox XRCE XFST/lexc/twolc compilers - FOMA - https://fomafst.github.io/ https://fomafst.github.io/