wrote on resource in tutorial

doc/tutorial/gf-tutorial2.txt

@@ -1752,17 +1752,51 @@ they can be used as arguments. For example:
 %--!
 ==More features of the module system==
 
+===Interfaces, instances, and functors===
+
 
 ===Resource grammars and their reuse===
 
-See 
-[resource library documentation  ../../lib/resource/doc/gf-resource.html]
+A resource grammar is a grammar built on linguistic grounds,
+to describe a language rather than a domain.
+The GF resource grammar library contains resource grammars for
+10 languages, is described more closely in the following
+documents:
+- [Resource library API documentation ../../lib/resource/doc/gf-resource.html]:
+  for application grammarians using the resource.
+- [Resource writing HOWTO ../../lib/resource-1.0/doc/Resource-HOWTO.html]:
+  for resource grammarians developing the resource.
 
 
-===Interfaces, instances, and functors===
+However, to give a flavour of both using and writing resource grammars,
+we have created a miniature resource, which resides in the
+subdirectory [``resource`` resource]. Its API consists of the following
+modules:
+- [Syntax resource/Syntax.gf]: syntactic structures, language-independent
+- [LexEng resource/LexEng.gf]: lexical paradigms, English
+- [LexIta resource/LexIta.gf]: lexical paradigms, Italian
+
+
+Only these three modules should be ``open``ed in applications.
+The implementations of the resource are given in the following four modules:
+- [MorphoEng resource/MorphoEng.gf],
+  [MorphoIta resource/MorphoIta.gf]: low-level morphology
+- {SyntaxEng resource/SyntaxEng.gf].
+  [SyntaxIta resource/SyntaxIta.gf]: definitions of syntactic structures
+
+
+An example use of the resource resides in the
+subdirectory [``applications`` applications].
+It implements the abstract syntax 
+[``FoodComments`` applications/FoodComments.gf] for English and Italian.
+The following diagram shows the module structure, indicating by
+colours which modules are written by the grammarian. The two blue modules
+form the abstract syntax. The three red modules form the concrete syntax.
+The two green modules are trivial instantiations of a functor.
+The rest of the modules (black) come from the resource.
+
+[Multi.png]
 
-See an
-[example built this way ../../examples/mp3/mp3-resource.html]
 
 
 ===Restricted inheritance and qualified opening===