Tree Adjoining Grammars

DyAlog can compile Feature Tree Adjoining Grammars [FTAGs]. This extension is based on ftp://ftp.inria.fr/INRIA/Projects/Atoll/Eric.Clergerie/SD2SA.ps.gz. TAGs are compiled into (meta) transitions of a 2-stack automaton, which are then compiled into DyALog objects and application functions for a run-time tabular evaluation.

For instance, the following grammar defines the langage a^nb^nec^nd^n

tree s("e").
auxtree -s("a",s("b",*s,"c"),"d").

The first tree of this program is an initial tree reading the terminal "e" and allowing an adjonction on the node s.

The second tree is an auxiliary tree. Its foot node is the one marked by * and adjonction is not allowd on the node marked by -.

Mandatory adjonction may be marked by prefixing a node by ++.

TAG non terminals may be called from a Prolog program using predicate tag_phrase/3.

Nodes may be named and decorated with a pair of top and bot attributes.

Following the XTAG architecture, trees may be named and grouped in set of families. Each tree may have an anchor node, a distinguished node marked <>. Tree are related to lemma

The following is a fragment from a small french FTAG for verb donne (gives).

%% Specify wich parameter of trees in tn1pn2 may be instanciated
%% with information from the lexicon
:-tag_anchor{ name => tn1pn2,
              coanchors => [ p_2 ],
              equations => [ [A]^(top=np{ restr => A } at np_2),
                             [B]^(top=np{ restr => B } at np_0)
                           ]
            }.

%% Define tree tn1pn2 in family tn1pn2
%% anchored on a verb
tag_tree{ name => tn1pn2,
          family => tn1pn2,
          tree=> tree
        bot=s{mode => X2, inv => (-)}
        at s(
             id=np_0
            and top=np{num => X0, pers => X1, wh => (-)}
            at np,
             top=vp{num => X0, pers => X1, mode => X2}
            and bot=vp{mode => X3, num => X6, pers => X7}
            at vp(
                  bot=v{mode => X3, num => X6, pers => X7}
                 at <> v,
                  np,
                  pp(
                     id=p_2 at p,
                     id=np_2 at np
                    )
                 )
            )
        }.

%% Define lemma entry in the lexicon for verb DONNER (to give)
tag_lemma('*DONNER*',v,
          tag_anchor{ name=>tn1pn2,
                       coanchors=>[p_2=à],
                       equations=>[top = np{ restr=>plushum } at np_0,
                                   top = np{ restr=>plushum } at np_2]}
         ).

%% Define morph entry in the lexicon for verb donne (gives)
tag_lexicon(donne, '*DONNER*', v, 
            v{ mode => mode[ind, subj], num => sing }).

Modulation may be applied on TAG non terminals.

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