1% This file is part of the Attempto Parsing Engine (APE).
    2% Copyright 2008-2013, Attempto Group, University of Zurich (see http://attempto.ifi.uzh.ch).
    3%
    4% The Attempto Parsing Engine (APE) is free software: you can redistribute it and/or modify it
    5% under the terms of the GNU Lesser General Public License as published by the Free Software
    6% Foundation, either version 3 of the License, or (at your option) any later version.
    7%
    8% The Attempto Parsing Engine (APE) is distributed in the hope that it will be useful, but WITHOUT
    9% ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
   10% PURPOSE. See the GNU Lesser General Public License for more details.
   11%
   12% You should have received a copy of the GNU Lesser General Public License along with the Attempto
   13% Parsing Engine (APE). If not, see http://www.gnu.org/licenses/.
   14
   15
   16:- module(drs_to_ruleml, [
   17		drs_to_ruleml/2
   18		]).

   38% The following operators are used in the DRS.
   39:- op(400, fx, -).   40:- op(500, xfx, =>).   41:- op(500, xfx, v).

 drs_to_ruleml(+Drs:drs, -RuleML:functor) is det

Turn the DRS into RuleML/folog (in SWI Prolog's internal XML format) as specified in David Hirtle's thesis.

   49drs_to_ruleml(
   50	DRS,
   51	element('RuleML', [], [
   52		element('Assert', [], Elements)
   53	])
   54	) :-
   55	existdrs_els(DRS, Elements).

 conds_and(+Conds:list, -Element:functor) is det

Converts a list of DRS conditions into a RuleML and-element.

   62conds_and(Conds, ElementsOut) :-
   63	conds_elements(Conds, Elements),
   64	conds_and_x(Elements, ElementsOut).
   65
   66conds_and_x([Element], Element) :-
   67    !.
   68
   69conds_and_x(Elements, element('And', [], Elements)).

 conds_elements(+Conds:list, -Elements:list) is det

Converts a list of DRS conditions into RuleML elements.

   76conds_elements([], []).
   77
   78conds_elements([Cond | Tail], [SCond | STail]) :-
   79	cond_element(Cond, SCond),
   80	conds_elements(Tail, STail).

 cond_element(+Condition:functor, -Element:functor) is det

Converts a DRS condition into a RuleML element.

As the structure of the DRS doesn't match exactly to the structure of the RuleML element (as specified by Hirtle), we have to do some ugly appending.

   91cond_element(drs(Dom1, Conds1) => DRS2,
   92	element('Forall', [], SubElements0)
   93	) :-
   94	args_els(Dom1, VarElements1),
   95	conds_and(Conds1, Element1),
   96	existdrs_els(DRS2, SubElements2),
   97	append([Element1], SubElements2, SubElements1),
   98	append(VarElements1, [element('Implies', [], SubElements1)], SubElements0).
   99
  100
  101cond_element(DRS1 v DRS2,
  102	element('Or', [], SubElements0)
  103	) :-
  104	existdrs_els(DRS1, SubElements1),
  105	existdrs_els(DRS2, SubElements2),
  106	append(SubElements1, SubElements2, SubElements0).
  107
  108
  109cond_element(-DRS, element('Neg', [], SubElements)) :-
  110	existdrs_els(DRS, SubElements).
  111
  112
  113cond_element(Conds, Element) :-
  114	is_list(Conds),
  115	conds_and(Conds, Element).
  116
  117
  118cond_element(Condition-_, element('Atom', [], [element('Rel', [], [Functor]) | Els])) :-
  119	Condition =.. [Functor | Args],
  120	args_els(Args, Els).

 args_els(+List:list, -Elements:list) is det

Converts the arguments of a DRS condition into RuleML elements.

Note that all terms (e.g. variables and numbers) must be converted into atoms to be compatible with the way how SWI represents XML documents internally.

  131args_els([], []).
  132
  133args_els([H | T], [element('Var', [], [HH]) | ElsTail]) :-
  134	var(H),
  135	!,
  136	term_to_atom(H, HH),
  137	args_els(T, ElsTail).
  138
  139args_els([H | T], [element('Data', [], [HH]) | ElsTail]) :-
  140	number(H),
  141	!,
  142	term_to_atom(H, HH), % alternatively: atom_number(HH, H)
  143	args_els(T, ElsTail).
  144
  145args_els([H | T], [element('Ind', [], [H]) | ElsTail]) :-
  146	args_els(T, ElsTail).

 existdrs_els(+Drs:drs, -Elements:list) is det

Converts an existential DRS box into RuleML elements.

  153existdrs_els(drs([],Conds), [Element]) :-
  154    !,
  155	conds_and(Conds, Element).
  156
  157existdrs_els(drs(Dom,Conds), [element('Exists', [], Elements)]) :-
  158	args_els(Dom, DomElements),
  159	conds_and(Conds, Element),
  160	append(DomElements, [Element], Elements).

 to_xml(+Elements:list, -Xml:atom) is det

Arguments:

Elements	- is a list of XML elements
Xml	- is an XML document as an atom

deprecated

- use SWI's xml_write/3 instead

Converts SWI Prolog's XML represenation into an XML atom. Something like xml_write/3 but very simple.

  173to_xml([], '').
  174
  175to_xml([element(Name, _, Elements) | T], Xml) :-
  176	to_xml(Elements, ElXml),
  177	to_xml(T, TXml),
  178	format(atom(Xml), '<~w>~w</~w>~n~w', [Name, ElXml, Name, TXml]).
  179
  180to_xml([Text | T], Xml) :-
  181	atom(Text),
  182	to_xml(T, TXml),
  183	format(atom(Xml), '~w~w', [Text, TXml])