I think that your mistake is in your goal. Notice some points:
1. In goal you can not make any rules.
2.You should use clauses which have one unknown parameter at least. Otherwise the prolog gives you 'Yes' or 'No' answer.
3.'landlocked' is a base predicates. Therefore must added in the clauses.
Predicates
country(symbol)
island(symbol)
sea(symbol)
lake(symbol)
ocean(symbol)
landlocked(symbol)
adjacent(symbol,symbol)
borders(symbol,symbol)
waterbody(symbol)
Clauses
landlocked(mali).
country(morocco).
country(algeria).
country(tunisia).
country(libya).
country(egypt).
country(sudan).
country(chad).
country(niger).
country(mali).
country(mauritania).
country(cape_verde).
country(senegal).
country(gambia).
country(guinea_bissau).
country(guinea).
country(sierra_leone).
country(liberia).
country(ivory_coast).
country(burkina_faso).
country(ghana).
country(togo).
country(benin).
country(nigeria).
country(cameroon).
country(central_african_republic).
country(equatorial_guinea).
country(gabon).
country(congo).
country(democratic_republic_congo).
country(rwanda).
country(burundi).
country(kenya).
country(uganda).
country(tanzania).
country(ethiopia).
country(eritrea).
country(djibouti).
country(somalia).
country(angola).
country(zambia).
country(malawi).
country(zimbabwe).
country(mozambique).
country(botswana).
country(namibia).
country(swaziland).
country(lesotho).
country(south_africa).
island(madagascar).
island(comoros).
island(mauritius).
island(reunion).
sea(red).
sea(mediterranean).
ocean(atlantic).
ocean(indian).
lake(malawi).
lake(tanganyika).
lake(victoria).
adjacent(egypt,red).
adjacent(sudan,red).
adjacent(eritrea,red).
adjacent(djibouti,red).
adjacent(somalia,red).
adjacent(mediterranean,red).
adjacent(indian,red).
adjacent(kenya,indian).
adjacent(tanzania,indian).
adjacent(mozambique,indian).
adjacent(madagascar,indian).
adjacent(mauritius,indian).
adjacent(comoros,indian).
adjacent(mozambique,indian).
adjacent(south_africa,indian).
adjacent(reunion,indian).
adjacent(red,indian).
adjacent(atlantic,indian).
adjacent(south_africa,atlantic).
adjacent(namibia,atlantic).
adjacent(angola,atlantic).
adjacent(congo,atlantic).
adjacent(gabon,atlantic).
adjacent(cameroon,atlantic).
adjacent(nigeria,atlantic).
adjacent(benin,atlantic).
adjacent(togo,atlantic).
adjacent(ghana,atlantic).
adjacent(ivory_coast,atlantic).
adjacent(liberia,atlantic).
adjacent(sierra_leone,atlantic).
adjacent(guinea_bissau,atlantic).
adjacent(gambia,atlantic).
adjacent(senegal,atlantic).
adjacent(cape_verde,atlantic).
adjacent(mauritania,atlantic).
adjacent(morocco,atlantic).
adjacent(guinea,atlantic).
adjacent(equatorial_guinea,atlantic).
adjacent(mediterranean,atlantic).
adjacent(morocco,mediterranean).
adjacent(libya,mediterranean).
adjacent(egypt,mediterranean).
adjacent(algeria,mediterranean).
adjacent(tunisia,mediterranean).
waterbody(lake).
waterbody(sea).
waterbody(ocean).
borders(A,B):-adjacent(A,B).
borders(A,B):-adjacent(B,A).
borders(B,A):-adjacent(A,B).
borders(B,A):-adjacent(B,A).
borders(kenya,victoria).
borders(uganda,victoria).
borders(tanzania,victoria).
Goal
landlocked(X), country(X),not(adjacent(X,_)),
/* landlocked(X).All landlocked couintries*/
/* adjacent(X,atlantic).Features adjacent to Atlantic Ocean*/
/* adjacent(X,red).oceans,lakes,countries,seas,islands*/
adjacent(victoria,X).
Now it run without problems. I hope that's clear, if you have some other problems you can contact me.
My E_mail: novapar@yahoo.com
<Parvin Abedi>
