A simple natural language dialogue system using Prolog

Introduction

Here is a natural language dialogue system that answers simple queries given by human. Basically, it is a template system, with simplification rules and translation rules, written in SWI-Prolog to convert human queries into commands.

Each query is processed in the following way:

1. Split the query into a list of words.
2. Convert all letters of the words into lower case letters.
3. Apply simplification rules to reduce the words into a short sentence.
4. Apply translation rules to convert the short sentence into a command.
5. Execute the command. For this system, a message is returned to the human.

Sample Dialogue

In the dialogue below,

1. |: query asked by human
2. [ query splitted into words with lower case letters ]
3. [ simplified sentence ]
4. [ command to be executed ]
5. The sentence between a pair of --- are answered by the system.

Type a query below, [Enter]: |: How are you [how,are,you] [greet] [greet] --- I am fine, thank you. --- Type a query below, [Enter]: |: What's you name [what's,you,name] [get,name] [unknownQry] --- Sorry, I don't understand what you mean, please ask in another way. --- Type a query below, [Enter]: |: What's your name [what's,your,name] [get,sysName] [sysName] --- I am AI-1, a very smart AI, thank you for using me. --- Type a query below, [Enter]: |: Nice to meet you [nice,to,meet,you] [nice,to,meet] [unknownQry] --- Sorry, I don't understand what you mean, please ask in another way. --- Type a query below, [Enter]: |: what is the time [what,is,the,time] [get,sysTime] [sysTime] --- 06:33:27 PM HKT --- Type a query below, [Enter]: |: what is the date [what,is,the,date] [get,sysDate] [sysDate] --- Thursday, May 04, 2023 --- Type a query below, [Enter]: |: show me the date [show,me,the,date] [get,sysDate] [sysDate] --- Thursday, May 04, 2023 --- Type a query below, [Enter]: |: bye [bye] [quit] [quit] --- Bye. --- ?-

Source Code

% A very simple NLP example % % lower level functions % -------------------- % convert a list of atoms into % a list of lower case atoms lower([Y|X1], [Z|X2]) :- downcase_atom(Y,Z), lower(X1,X2). lower([], []). % simplification rules % -------------------- % key phrases sr([how,are,you|X], [greet|X]). sr([how,to,use|X], [help|X]). sr([how,do,you,do|X], [greet|X]). sr([who,are,you|X], [get,sysName|X]). sr([your,name|X], [sysName|X]). sr([time,now|X], [sysTime|X]). sr(['today\'s', date|X], [sysDate|X]). % stop words to be ignored sr([please|X], X). sr([know|X], X). sr([have|X], X). sr([can|X], X). sr([are|X], X). sr([the|X], X). sr([you|X], X). sr([for|X], X). sr([did|X], X). sr([is|X], X). sr([of|X], X). sr([me|X], X). sr([do|X], X). % unify words sr([which|X], [get|X]). sr([what|X], [get|X]). sr(['what\'s'|X], [get|X]). sr([give|X], [get|X]). sr([send|X], [get|X]). sr([show|X], [get|X]). sr([time|X], [sysTime|X]). sr([date|X], [sysDate|X]). sr([halt|X], [quit|X]). sr([exit|X], [quit|X]). sr([end|X], [quit|X]). sr([bye|X], [quit|X]). sr([''], [help]). % translation rules % ----------------- tr([greet], [greet]). tr([sysTime], [sysTime]). tr([sysDate], [sysDate]). tr([get,sysName], [sysName]). tr([get,sysTime], [sysTime]). tr([get,sysDate], [sysDate]). tr([get,help], [showHelp]). tr([help],[showHelp]). tr([quit], [quit]). % simplify query to short sentence % -------------------------------- simplify(List, Result) :- sr(List, NewList), !, simplify(NewList, Result). simplify([W|Words], [W|NewWords]) :- simplify(Words, NewWords). simplify([], []). % translate short sentence into command % ------------------------------------- translate(ShSent, Cmmd) :- tr(ShSent, Cmmd), !. translate(_,[unknownQry]). % actions % ------- action([unknownQry]) :- writeln('---'), writeln('Sorry, I don\'t understand what you mean, please ask in another way.'), writeln('---'), nl. action([greet]) :- writeln('---'), writeln('I am fine, thank you.'), writeln('---'), nl. action([sysName]) :- writeln('---'), writeln('I am AI-1, a very smart AI, thank you for using me.'), writeln('---'), nl. action([sysTime]) :- get_time(T), format_time(string(Time), "%X", T), writeln('---'), writeln(Time), writeln('---'), nl. action([sysDate]) :- get_time(T), format_time(string(Date), "%x", T), writeln('---'), writeln(Date), writeln('---'), nl. action([showHelp]) :- writeln('---'), writeln('Send me a query, [Enter]:'), writeln('1. What is the time now'), writeln('2. Give me today\'s date'), writeln('3. What is your name'), writeln('4. Who are you'), writeln('5. How are you'), writeln('6. ...'), writeln('---'), nl. action([quit]) :- writeln('---'), writeln('Bye.'), writeln('---'), nl. % main program % ------------ go :- repeat, writeln('Type a query below, [Enter]: '), read_line_to_codes(user_input, Codes), atom_codes(A,Codes), % convert Codes to an atom atomic_list_concat(AL1, ' ', A), % split an atom into atoms according lower(AL1, AL2), % to single space writeln(AL2), simplify(AL2, ShrtSent), writeln(ShrtSent), translate(ShrtSent, Cmmd), writeln(Cmmd), action(Cmmd), Cmmd == [quit], !. % start go after this script is loaded. :- initialization(go, program).