![[IJET V2I5P6] Authors: Maha M. A. Lashin, Ahmed A. Barakat , Ahmed M. Makady, Ahmed M. Aly](https://static.fdocuments.us/doc/165x107/587496f91a28abfc5f8b4977/ijet-v2i5p6-authors-maha-m-a-lashin-ahmed-a-barakat-ahmed-m-makady.jpg)
[IJET V2I5P6] Authors: Maha M. A. Lashin, Ahmed A. Barakat , Ahmed M. Makady, Ahmed M. Aly
LOGIC PROGRAMMING Chapter 1: Introduction Ahmed...
56
Ahmed Sallam Slides based on original lecture slides Dr. Temur Kutsia LOGIC PROGRAMMING Chapter 1: Introduction
Transcript of LOGIC PROGRAMMING Chapter 1: Introduction Ahmed...
Ahmed SallamSlides based on original lecture slides Dr. Temur Kutsia
LOG
IC PRO
GRA
MM
ING
Chapter 1: Introduction
"What" vs "How"
Declarative vs Procedural Programming
Procedural programming• The programmer has to specify how to get the output for
the range of required inputs.• The programmer must know the appropriate algorithm.
Declarative programming• Requires a more descriptive style.• The programmer must know what relationships hold
between various entities.
Introduction
2
10/07/2014
Example: List Concatenation
In procedural style:list procedure cat(list a,list b){
list t = list u = copylist(a);while (t.tail != nil) t = t.tail;t.tail = b;return u;
}
In declarative style:cat([], L, L).cat([H|T], L, [H|Z]) :- cat(T, L, Z).
Introduction
3
10/07/2014
Logic Programming
A declarative style programming paradigm . Computation through logical deduction . Uses the language of logic to express data and programs . Most of current logic programming languages use first
order logic (FOL). Prolog – the most popular logic programming language .
Introduction
4
10/07/2014
Historical Facts
1970-ies:
• Bob Kowalski . "Predicate Logic as a Programming Language".IFIP Congress, Stockholm
• Alain Colmerauer and his group .Interpreter of the first logic programming language Prolog. Marseille
Introduction
5
10/07/2014
Prolog
• Prolog is the main subject of this course• Used in Artificial Intelligence, Natural Language
Processing, Automated Reasoning, XML Querying ...
• Exists in many dialects (Sicstus Prolog, SWI Prolog,
Prolog IV, BinProlog, Ciao Prolog, Prolog LPA, Visual
Prolog, YAP Prolog, Strawberry Prolog (...• (Almost) all the dialects agree on the “core" part (ISO
Standard for Prolog)
Introduction
6
10/07/2014
Prolog in Industrial Applications
Clarissa :• A fully voice-operated procedure browser .• Developed at NASA .• Used on the International Space Station .• Enables astronauts to give full attention to the task while
they navigate through complex procedures using spokencommands .
• Implemented in SICStus Prolog .
Introduction
7
10/07/2014
Prolog in Industrial Applications
Some other solutions :• FleetWatch – fully integrated operations control and schedules
planning solution. Used by 21 international airlines, amongthem Comair (USA), Italian branch of Lauda Air, Malev(Hungary), DHL Europe, Asiana (South Korea), Hainan (China), Royal Jordanian, Kuwait Airways, Cimber Air (Denmark), etc .
• SCORE – a long term airport capacity management system for coordinated airports. Successfully Used at IATA SchedulingConferences. Users in more than 20 countries .
• ARGOS – a Decision Support System (DSS) for enhancingCrisis Management for incidents with Chemical, Biological,Radiological, and Nuclear (CBRN) releases .
Introduction
8
10/07/2014
Contents
Basics of PROLOG
Facts
Questions
Variables
Conjunction
Rules
Introduction
9
10/07/2014
PROLOG
Used to solve problems involving• objects, and• relationships between objects .
Introduction
10
10/07/2014
Relationships
ExampleJohn owns the book
• The relationship: ownership• The objects: book, John
Directional :• John owns the book• Not: The book owns John
Introduction
11
10/07/2014
PROLOG
Program can be thought of as a storehouse of facts and rules . Conversational Language: The user can ask questions about
the set of facts and rules in the PROLOG program .
Introduction
12
10/07/2014
PROLOG
Sisters Example : A rule defining sisters and the facts about the people involved . The user would ask :
Are these two people sisters ?
The system would answer yes (true) or no (false)
Introduction
13
10/07/2014
Programming in PROLOG
Declaring Facts about objects and their relationships . Defining Rules about objects and their relationships . Asking Questions about objects and their relationships .
Introduction
14
10/07/2014
Contents
Basics of PROLOG
Facts
Questions
Variables
Conjunction
Rules
Introduction
15
10/07/2014
Parts of Fact
0Introduction
16
10/07/2014
Order of Objects
Introduction
17
10/07/2014
Examples of Facts
ExampleGold is valuable .v a l u a b l e ( g o l d )
Jane is a female .f ema le ( j ane )
John owns some gold .owns( john,go ld )
John is the father of Mary .f a t h e r ( j o h n , m a r y )
Are these expressions really facts? Is there anything missing?
Introduction
18
10/07/2014
Interpretation of Names
The name refers to an object .
Semantic Meaning: Given by the programmer . Syntactic Meaning: a set of characters, as PROLOG sees it .
Introduction
19
10/07/2014
Interpretation of Names
Name refers to an object . Name gold can refer to :
a particular lump of gold, or the chemical element Gold having atomic number 79 .
v a l u a b l e ( g o l d ) can mean : that particular lump of gold, named gold, is valuable, or the chemical element Gold, named gold, is valuable .
The programmer decides (in her usage) the meaning .
Introduction
20
10/07/2014
Fact Terminology
Introduction
21
10/07/2014
Database
DefinitionIn PROLOG, database is a collection of facts .
PROLOG draws its knowledge from these facts . The programmer is responsible for their accuracy .
Introduction
22
10/07/2014
Contents
Basics of PROLOG
Facts
Questions
Variables
Conjunction
Rules
Introduction
23
10/07/2014
Questions
The database contains the facts from which the questions are answered .
A Question can look exactly like a fact : owns(mary,book) .
The difference is in which mode one is in
Introduction
24
10/07/2014
Questions
In the interactive question mode (indicated by the question mark and dash): ? -
Question: ? - owns(mary,book). Meanins: If mary is interpreted as a person called Mary, and book is
interpreted as some particular book, then
?- owns(mary,book). means: Does Mary own the book?
Introduction
25
10/07/2014
Database Search
ExampleFacts in the database:l i k e s ( j o e , f i s h ) .l i k e s ( j o e , m a r y ) .l i k e s ( m a r y ,b o o k ) .l i k e s ( j o h n , b o o k ) .
Questions :?- l i k e s ( j o e , m o n e y ) . no?- l i k e s ( j o e , m a r y ) . yes?- k i n g ( j o h n , f r a n c e ) . n o
Introduction
26
10/07/2014
Knowledge
The questions are always answered with respect to thedatabase .
ExampleFacts in the database:human(socrates) .h u m a n ( a r i s t o t l e ) .a t h e n i a n ( s o c r a te s ) .
Question :Is Socrates Greek ??- g reek (soc ra tes )
The answer with respect to this database is No.Introduction
27
10/07/2014
Questions
Up until now questions just reflect exactly the database .
Does Mary like the book ??- l i k e s ( m a r y ,b o o k ) .
More Interesting Question: What objects does Mary like ?
Variables .
Introduction
28
10/07/2014
Contents
Basics of PROLOG
Facts
Questions
Variables
Conjunction
Rules
Introduction
29
10/07/2014
Variables
Tiresome to ask about every object: l i k e s ( j o h n , t h i s ) .l i k e s ( j o h n , t h a t ) .
Better to ask :What does John like?orDoes John like X ?(i.e. use variables)
Introduction
30
10/07/2014
Question With Variables
Does John like X ?
? - l i k e s ( j o h n , X ) .or? - l i kes ( john ,Someth ingThatJohnL ikes) .
X and SomethingThatJohnLikes are variables.
Variable begins with a capital letter .
Introduction
31
10/07/2014
PROLOG Answer
Database :l i k e s ( j o h n , f l o w e r s ) .
Question :? - l i k e s ( j o h n , X ) .
PROLOG answers :X=f lowers
Introduction
32
10/07/2014
Many Answers
Database:l i k e s ( j o h n , f l o w e r s ) .l i k e s ( j o h n , m a r y ) .l i k e s ( p a u l , m a r y ) .
Question :? - l i k e s ( j o h n , X ) .
PROLOG answers :X=f lowersand the user acknowledgesX=maryand the user acknowledgesno
Introduction
33
10/07/2014
Placemarker
The first match is found: X=f lowers . The user acknowledges .
From that place on the next match is found (the search continues). From the place of the last instantiation no more match was found . Thus answer: no .
Introduction
34
10/07/2014
Contents
Basics of PROLOG
Facts
Questions
Variables
Conjunction
Rules
Introduction
35
10/07/2014
Conjunctions
More Complicated Relationships :
Does Mary like John and does John like Mary?
Both Conditions must be fulfilled .
Introduction
36
10/07/2014
Conjunctions
Database:
l i k e s ( m a r y , f o o d ) .l i k e s ( m a r y , w i n e ) .l i k e s ( j o h n , w i n e ) .l i k e s ( j o h n , m a r y ) .
Comma means Conjunction :
? - l i k e s ( j o h n , m a r y ) , l i k e s ( m a r y , j o h n ) .Answer: noA match for l i k e s ( j o h n , m a r y )but none for l i k e s ( m a r y , j o h n )
Introduction
37
10/07/2014
Conjunctions with Variables
Is there anything that both mary and john like ?
Find out what Mary likes and then see if John likes it .
? - l i k e s ( m a r y , X ) , l i k e s ( j o h n , X ) .
Introduction
38
10/07/2014
Backtracking
Find match for the first goal . Then see if matches the second . If not, find another match for the first . See if this matches the second . …etc .
Introduction
39
10/07/2014
Match First
Introduction
40
10/07/2014
Match Second
Introduction
41
10/07/2014
Backtrack
Introduction
42
10/07/2014
Success
Introduction
43
10/07/2014
Contents
Basics of PROLOG
Facts
Questions
Variables
Conjunction
Rules
Introduction
44
10/07/2014
Rules
• How to express that John likes all people?• Listing all people?
• likes(john, alfred).• likes(john, bertrand).• likes(john, charles).• likes(john, david).• etc.
• Not feasible. More compact way: Using rules.John likes any object provided it is a person.
Introduction
45
10/07/2014
Rule Examples
Rules state Dependence :
I use an umbrella if there is rain .
Rules Define:
X is a bird if X is an animal and X has feathers.
Introduction
46
10/07/2014
Formulating Rules
John likes anyone who likes wine .
John likes any Something if it likes wine .
John likes X if X likes wine .
Introduction
47
10/07/2014
Rule Syntax
Introduction
48
10/07/2014
Variable Scope
The occurrences of X within a rule refer to the same object :
l i k e s ( j o h n , X ) : - l i k e s ( X , w i n e ) , l i k e s ( X , f o o d ) .
l i k e s ( j o h n , mary):-l i k e s ( m a r y , w i n e ) , l i k e s ( m a r y , f o o d ) .l i k e s ( j o h n , adam):- l i kes (adam , w i n ) , l i kes (adam, f o o d ) .
Introduction
49
10/07/2014
Royal Parents
Example
The parents of X are Y and Z .Y is the mother .Z is the father .
Database :
m a l e ( a l b e r t ) .male(edward).f e m a l e ( a l i c e ) .f e m a l e ( v i c t o r i a ) .p a r e n t s ( e d w a r d , v i c t o r i a , a l b e r t ) .p a r e n t s ( a l i c e , v i c t o r i a , a l b e r t ) .
Introduction
50
10/07/2014
Sisters
ExampleX is a sister of Y if :
X is female ,X has parents M and F ,Y has parents M and F .
Rule :
s i s t e r ( X , Y ) : - f ema le (X ) ,pa ren ts (X ,M,F) ,pa ren ts (Y ,M,F) .
Introduction
51
10/07/2014
Sisters Question
Question :
? - s i s t e r ( a l i c e , e d w a r d ) .
The question (goal) matches the head of the rule, if onereplaces X with a l i c e and Y with edward.The instance of the body becomes new
goal: female(a l i c e ) ,pa ren ts (a l i c e , M , F ) ,pa ren ts (edward, M , F ) .
Introduction
52
10/07/2014
7 s i s t e r ( a l i c e , e d w a r d )X0=a l i ce ,Y0=edward
3 f e m a l e ( a l i c e ) ,p a r e n t s ( a l i c e , M 0 , F 0 ) ,parents(edward,M0,F0).
6 p a r e n t s ( a l i c e , M 0 , F 0 ) ,parents(edward,M0,F0).
M 0 = v i c t o r i a ,F0=a lber t
5 p a r e n t s ( e d w a r d , v i c t o r i a , a l b e r t ) .
•
Is Alice Edward’s Sister?
( 1 ) m a l e ( a l b e r t ) .
(2) male(edward).
( 3 ) f e m a l e ( a l i c e ) .
( 4 ) f e m a l e ( v i c t o r i a ) .
(5) parents(edward,
v i c t o r i a , a l b e r t ) .
( 6 ) p a r e n t s ( a l i c e ,
v i c t o r i a , a l b e r t ) .
( 7 ) s i s t e r ( X , Y ) : -
f ema le (X) ,
pa ren ts (X ,M,F) ,
pa ren ts (Y ,M,F ) .
Introduction
53
10/07/2014
Is Alice Edward’s Sister?
7 s i s t e r ( a l i c e , e d w a r d )X0=a l i ce ,Y0=edward
3 f e m a l e ( a l i c e ) ,p a r e n t s ( a l i c e , M 0 , F 0 ) ,parents(edward,M0,F0).
6 p a r e n t s ( a l i c e , M 0 , F 0 ) ,parents(edward,M0,F0).
M 0 = v i c t o r i a ,F0=a lber t
5 p a r e n t s ( e d w a r d , v i c t o r i a , a l b e r t ) .
•
Introduction
54
10/07/2014
( 1 ) m a l e ( a l b e r t ) .
(2) male(edward).
( 3 ) f e m a l e ( a l i c e ) .
( 4 ) f e m a l e ( v i c t o r i a ) .
(5) parents(edward,
v i c t o r i a , a l b e r t ) .
( 6 ) p a r e n t s ( a l i c e ,
v i c t o r i a , a l b e r t ) .
( 7 ) s i s t e r ( X , Y ) : -
f ema le (X) ,
pa ren ts (X ,M,F) ,
pa ren ts (Y ,M,F ) .
Who’s Sister Is Alice?
7 s i s t e r ( a l i c e , X )X0=a l i ce ,Y0=X
3 f e m a l e ( a l i c e ) ,p a r e n t s ( a l i c e , M 0 , F 0 ) ,parents (X,M0,F0) .
6 p a r e n t s ( a l i c e , M 0 , F 0 ) ,parents (X,M0,F0) .
M0=v ic to r iaF0=a lber t
5 p a r e n t s ( X , v i c t o r i a , a l b e r t ) .
X=edward
•
Answer: X = edward.Introduction
55
10/07/2014
( 1 ) m a l e ( a l b e r t ) .
(2) male(edward).
( 3 ) f e m a l e ( a l i c e ) .
( 4 ) f e m a l e ( v i c t o r i a ) .
(5) parents(edward,
v i c t o r i a , a l b e r t ) .
( 6 ) p a r e n t s ( a l i c e ,
v i c t o r i a , a l b e r t ) .
( 7 ) s i s t e r ( X , Y ) : -
f ema le (X) ,
pa ren ts (X ,M,F) ,
pa ren ts (Y ,M,F ) .
Useful Links
• SWI-Prolog:• http://www.swi-prolog.org/
• SWI-Prolog Editor (Windows, SWI-x86 only) http://lakk.bildung.hessen.de/netzwerk/faecher/informatik/swiprolog/indexe.html
• Prolog mode for (X)Emacs:http://turing.ubishops.ca/home/bruda/emacs-prolog/
• Prolog newsgroup:http://groups.google.com/groups?group=comp.lang.prolog
• Links from SWI-Prolog Web page:http://www.swi-prolog.org/Links.html
Introduction
56
10/07/2014
