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+Guide to GF Implementation Code
+Aarne Ranta
+
+
+
+This document describes the code in GF grammar compiler and interactive
+environment. It is aimed to cover well the implementation of the forthcoming
+GF3. In comparison to GF 2.8, this implementation uses
+- the same source language, GF (only slightly modified)
+- a different run-time target language, GFCC (instead of GFCM)
+- a different separate compilation target language (a fragment GF itself, 
+  instead of GFC)
+- a different internal representation of source code
+
+
+Apart from GFCC, the goal of GF3 is simplification and consolidation, rather
+than innovation. This is shown in particular in the abolition of GFC, and in
+the streamlined internal source code format. The insight needed to achieve
+these simplifications would not have been possible (at least for us) without
+years of experimenting with the more messy formats; those formats moreover
+grew organically when features were added to the GF language, and the old
+implementation was thus a result of evolution rather than careful planning.
+
+GF3 is planned to be released in an Alpha version in the end of 2007, its
+sources forming a part of GF release 2.9.
+
+There are currently two versions of GF3, as regards executables and ``make`` 
+items:
+- ``gf3``, using the old internal representation of source language, and
+  integrating a compiler from GF to GFCC and an interpreter of GFCC
+- ``testgf3``, using the new formats everywhere but implementing the compiler
+  only; this program does not yet yield reasonable output
+
+
+The descriptions below will target the newest ideas, that is, ``textgf3`` 
+whenever it differs from ``gf3``.
+
+
+==The structure of the code==
+
+Code that is not shared with GF 2.8 is located in subdirectories of 
+``GF/Devel/``. Those subdirectories will, however, be moved one level
+up. Currently they include
+- ``GF/Devel/Grammar``: the datatypes and basic operations of source code
+- ``GF/Devel/Compile``: the phases of compiling GF to GFCC
+
+
+The other directories involved are
+- ``GF/GFCC``: data types and functionalities of GFCC
+- ``GF/Infra``: infrastructure utilities for the implementation
+- ``GF/Data``: datastructures belonging to infrastructure
+
+
+==The source code implementation==
+
+==The compiler==
+
+==The GFCC interpreter==
+
+==The GF command interpreter==
+
+
+
+
+
+