An exchange format for ELAN programs, called REF format for ``Reduced
ELAN Format'', provides a representation
of programs that can be shared by the different tools of the ELAN environment
such as the parser, the interpreter, the preprocessor and the compiler.
Such a format facilitates the connection to other systems, like ASF+SDF,
to execute ELAN programs with ASF+SDF or conversely. Another advantage
of REF format is to provide a term-like representation that can
be easily handled by ELAN programs (a module specifying the REFformat
is available in the library). For example, the unlabelled rules of an ELAN
program may be completed using a completion process to provide a confluent
and terminating rewrite system. Such a representation and functionalities
that allow to access and modify different parts of the format, are the
basis for implementing reflection in ELAN.