Change database via GUI in XPCE

1) How I can change my database (facts) using buttons and text fields in XPCE? For example, I have a set of facts:

country('Austria',84,8200,3900).
country('Belgium',30,10300,36500).
country('Bulgaria',1111,7323,11800).
country('United_Kingdom',245,60776,35300).
% and so on

And I've made some groups with GUI for change, edit or delete existing fact:

    new(AddNewName, text_item('Enter new country here:')),
    new(AddNewPop, text_item('Enter new country population:')),
    new(AddNewArea, text_item('Enter new country area:')),
    new(AddNewGDP, text_item('Enter new country GDP:')),
    send(H10, append, AddNewName),
    send(H10, append, AddNewPop),
    send(H10, append, AddNewArea),
    send(H10, append, AddNewGDP),
    send(H10, append, button(add)), %message(@prolog, memberCountry, Etiq, Result))), what should be here?
    send(H10, alignment, left),

    new(EditNewName, text_item('Enter country here:')),
    new(EditNewPop, text_item('Enter new country population:')),
    new(EditNewArea, text_item('Enter new country area:')),
    new(EditNewGDP, text_item('Enter new country GDP:')),
    send(H11, append, EditNewName),
    send(H11, append, EditNewPop),
    send(H11, append, EditNewArea),
    send(H11, append, EditNewGDP),
    send(H11, append, button(edit)), %message(@prolog, memberCountry, Etiq, Result))), what should be here?
    send(H11, alignment, left),

    new(DeleteNewName, text_item('Enter country name here:')),
    send(H12, append, DeleteName),
    send(H12, append, button(delete)), %message(@prolog, memberCountry, Etiq, Result))), what should be here?
    send(H12, alignment, left),

So, how I should construct my buttons messages?

2) And my second question is why I cant see the result of my deep-first search? Here is my GUI code and fucntion:

    new(Path1, text('6) Path form-to (serach in deep)')),
    new(From1, text_item('Enter country FROM here:')),
    new(To1, text_item('Enter country TO here:')),
    send(H2, append, Path1),
    send(H2, append, From1),
    send(H2, append, To1),
    new(Path1Res, list_browser),
    send(H2, append, button(path, message(@prolog, dfs, From1?selection, To1?selection, [], [], Path1Res))),
    send(H2, append, Path1Res),
    send(Path1Res, alignment, center),
%...
dfs(From, To, _, [(From, To)]):-
  border(From, To).
dfs(From, To, VisitedNodes, [(From, X)|TailPath], Path1):-
  border(From, X),
  not(member(X, VisitedNodes)),
  dfs(X, To, [From|VisitedNodes], TailPath),
  send(Path1, append, TailPath).

Thanks in advance!

Solution

For the first question, I think you should read the database from a file country.pl, declare predicate country/4 as dynamic, and save the whole database at the end of the program.

send(H11, append, button(edit)), %message(@prolog, addCountry, AddNewName?selection, AddNewPop?selection, AddNewArea?selection, AddNewGDP?selection))), what should be here?

May be :

addCountry(Name, Pop, Area, Gdb) :-
    assert(country(Name, Pop, Area, Gdb)).

For

editCountry(Name, Pop, Area, Gdb) :-
    retract(country(Name, _, _, _)),
    assert(country(Name, Pop, Area, Gdb)).

Here is an example of what can be done (Question 2)

showForm :-
    %new(W,  window('Test', size(800, 800))),
    new(D, dialog('Main window', size(800, 800))),
    new(H1, dialog_group(' ')),
    new(H2, dialog_group(' ')),
    new(H3, dialog_group(' ')),
    send(D, append, H1),
    send(D, append, H2, right),
    send(D, append, H3),
    /* 6) serach if country is in Europe */
    new(Etiq, text_item('1) Enter country here:')),
    send(H1, append, Etiq),
    new(Result, label),
    send(H1, append, Result),
    send(H1, append, button(search)),
    new(Lb, list_browser),

    /* 7) Path form-to (serach in deep) */
    new(Path1, text('6) Path form-to (search in deep)')),
    new(From, text_item('Enter country FROM here:')),
    new(To, text_item('Enter country TO here:')),
    send(H2, append, Path1),
    send(H2, append, From),
    send(H2, append, To),
    send(H2, append, 
         button(path, 
                message(@prolog, search, From?selection, To?selection, Lb))),
    send(H3, append, Lb),
    send(D, open),
    get(H2, height, HS2),
    send(H1, height, HS2-8),
    get(D, width, WD),
    send(H3, width, WD-30).

search(From, To, Lb) :-
    send(Lb, clear),
    send(Lb, append, From),
    send(Lb, append, To).

EDIT1 To save the new bdd you can do :

% Bdd holds the complete path to the bdd (for example c:\users\me\prolog\bdd\country.pl)
save(Bdd) :-
    tell(Bdd),
    listing(country),
    told.

EDIT2

I suppose that Way is a list of this kind [paris, calais, dover, london], you can do

search(From, To, Lb) :-
    %% get the path from Paris to London
    %% Way= [paris, calais, dover, london]
    send(Lb, clear),
    forall(member(X, Way), send(Lb, append, X)).