new resource doc on Phrase etc

lib/resource-1.0/abstract/Phrase.gf

@@ -1,21 +1,43 @@
+--1 Phrases and utterances
+
 abstract Phrase = Cat, Tense ** {
 
+-- When a phrase is built from an utterance it can be prefixed
+-- with a phrasal conjunction (such as "but", "therefore")
+-- and suffixing with a vocative (typically a noun phrase).
+
   fun
-    PhrUtt  : PConj -> Utt -> Voc -> Phr ;
+    PhrUtt   : PConj -> Utt -> Voc -> Phr ; -- But go home my friend.
 
-    UttS    : S -> Utt ;
-    UttQS   : QS -> Utt ;
-    UttImpSg, UttImpPl  : Pol -> Imp -> Utt ;
+-- Utterances are formed from sentences, questions, and imperatives.
 
-    UttIP   : IP   -> Utt ;
-    UttIAdv : IAdv -> Utt ;
-    UttNP   : NP   -> Utt ;
-    UttAdv  : Adv  -> Utt ;
-    UttVP   : VP   -> Utt ;
+    UttS     : S -> Utt ;                   -- John walks
+    UttQS    : QS -> Utt ;                  -- is it good
+    UttImpSg : Pol -> Imp -> Utt;           -- (don't) help yourself
+    UttImpPl : Pol -> Imp -> Utt;           -- (don't) help yourselves
 
-    NoPConj : PConj ;
-    PConjConj : Conj -> PConj ;
+-- There are also 'one-word utterances'. A typical use of them is
+-- as answers to questions.
+-- *Note*. This list is incomplete. More categories could be covered.
+-- Moreover, in many languages e.g. noun phrases in different cases
+-- can be used.
+
+    UttIP   : IP   -> Utt ;                 -- who
+    UttIAdv : IAdv -> Utt ;                 -- why
+    UttNP   : NP   -> Utt ;                 -- this man
+    UttAdv  : Adv  -> Utt ;                 -- here
+    UttVP   : VP   -> Utt ;                 -- to sleep
+
+-- The phrasal conjunction is optional. A sentence conjunction
+-- can also used to prefix an utterance.
+
+    NoPConj   : PConj ;                      
+    PConjConj : Conj -> PConj ;             -- and
+
+-- The vocative is optional. Any noun phrase can be made into vocative,
+-- which may be overgenerating (e.g. "I").
 
     NoVoc   : Voc ;
-    VocNP   : NP -> Voc ;
+    VocNP   : NP -> Voc ;                   -- my friend
+
 }