Source : Free On-Line Dictionary of Computing

Estelle
     
        A {Pascal} extension for formal specification of computer
        {network} {protocol}s.  Protocols are described by {modules}
        which are communicating {NFA}s.  Modules are arranged in a
        dynamic hierarchy and communicate at named interaction points.
     
        {EstPC (ftp:osi.ncsl.nist.gov/pub/osikit/estpc)} Compiles
        Estelle into C.  {petdingo} Translates Estelle into C++
     
        Adopted by {ITU-T}.  ISO 9074 (1989).
     
        ["The Formal Description Technique Estelle", M.  Diaz et al
        eds, N-H 1989].