Turbo Prolog 173 ACR

12 March'09 Turbo Programming 1

Seminar onPROLOG

Subject: Intelligent Systems

Prepared by:Nirali RathodME-II (ACR)Roll No.:173


Contents

Introduction to Prolog How to use Turbo Prolog Facts, Objects and Predicates Prolog variables Using rules Simple input and output


What is prolog

“PROgramming in LOGic” Developed by Alain Colmerauer and P. Roussel

in 1972 at the university of Marseilles in France. Supports formal symbolic reasoning


Features of Prolog

1. Can compile stand alone programs.2. A full complement of standard predicates is

available.3. A functional interface to other languages is

provided.4. Declared variables are used to provide more

secure development control.


Conti…

5. Both integer and floating point arithmetic supported.

6. Program development, compilation and debugging is very easy because of integrated editor.


How Prolog is different

Turbo prolog, like other implementations of Prolog,is an object oriented language.

Prolog uses only data about objects and their relationships.

User defines the goal,and the computer must find both the procedure and solution.

Prolog program is a collection of data or facts and their relationships among these facts.-program is database.


How Prolog is different

What is known about the problem is stored as data.

The user defines a goal, or hypothesis, and the program, using formal reasoning, attempts to prove or disprove the goal based on the known data.


Comparison

Procedural languages

Use previously defined procedures to solve problems

Most efficient at numerical processing

Systems created and maintained by programmers

Use structured programming

Object-oriented languages

Use heuristics to solve problems

Most efficient at formal reasoning

Systems developed and maintained by knowledge engineers

Interactive and cyclic development


Starting Turbo Prolog


Fundamental of Prolog

Declaring some facts Defining some rules Asking question


Starting with Prolog

Editor window: It is used to create program. Dialog window: when the program is executing,

output will be in the Dialog window. Message window: It keeps you up to date on

processing activity. Trace window: It is useful for finding problems in

the programs you create.


Editor: to create or edit program


Dialog: output


Message: processing activity


trace: finding problems in the program


Six options

Edit Files Compile Run Options Setup


Creating a sample program

Select the edit mode and enter the program. Enter the text or make corrections as necessary. Save the program to disk using the file save

option. Compile the program. Execute the program.







Expressing facts

Main part of prolog program consists of collection of knowledge about specific subject.


Expressing facts

Main part of prolog program consists of collection of knowledge about specific subject.

database

Rules

facts


Expressing facts

Prolog permits to describe facts in terms of symbolic relationships.

E.g.. Right speaker is not emitting sound: English : The right speaker is dead. Prolog : is(right_speaker,dead)


Expressing facts


E.g.. Right speaker is not emitting sound: English : The right speaker is dead. Prolog : is(right_speaker,dead).

Relation: Defines the way in which a collection of Objects belong together


Expressing facts



Objects: Name of an element of certain typeRepresents entity or property of entity(Elements within parentheses are arguments of Predicate)


Expressing facts



Predicate :function with a value true or false.Express property of a relationship


Expressing facts



Predicate + period = complete clause


clauses

facts Rules

predicates Periods(.)

relations

arguments

objects

variables

Relationship of clauses, predicates, relations and objects


Turbo prolog data types

variables Non variables

objects other

symbol

string

integer

real

char

file

list

Compound object



Prolog Variables

Variable can be used in Turbo Prolog clause or goal to specify an unknown quantity.

A variable name must be begin with a capital letter.

For example,

symptom(Disease,runny_nose)

variable is Disease.



variables Non variables

objects other

symbol

string

integer

real

char

file

list

Compound object


Must begin with an upper case letterEg. Age Patient



Variables:

No global variable. All variables are local to the clause of which they

are a part.


Unification

The process by which prolog tries to match a term against the facts or the heads of other rules in an effort to prove goal is called unification.

Predicates unify each other if : They have the same relation name. They have the same number of

arguments. All argument pairs unify with each other.


Unification

The process by which prolog tries to match a term against the facts or the heads of other rules in an effort to prove goal is called unification

Predicates unify each other if : They have the same relation name. They have the same number of

arguments. All argument pairs unify with each other.

Similar to parameter passing in programming


Compound goals

Goal : symptom(Diesease,runny_nose)and

symptom(Diesease,mild_body_ache)

Disease = cold

1 solution

Goal :



Symptom(Diesease,runny_nose)

Clause 1

Clause 2

Clause 3

Clause 4

Clause 5

Symptom(cold,runny_nose)

Clause 1

Clause 2

Clause 3

Symptom(cold,mild_body_ache)

Goal succeeds

Clause 1

Clause 2


Backtracking

If any condition in the chain fails, Prolog backtracks to previous condition, moves relentlessly forward and backward

through the conditions, trying every available binding in an attempt to

get the goal to succeed as many ways as

possible. It find its own way.




Using Rules

A rule is an expression that indicates the truth of a particular fact depending upon one or more facts

X is sister of Y If X is female And parents of X are M and F And parents of Y are M and F


Using Rules

The process of using rules to solve problems is called formal reasoning

It gives prolog the ability of decision making.


Arithmetic Operators

+ addition - subtraction * multiplication / real division // integer division ** power Goal : X is 3*4.

X = 12yes


Logical Operators

a :- b. /* a if b */ a :- b,c. /* a if b and c.*/ a :- b;c. /* a if b or c.*/ a :- \++ b. /* a if b is not provable*/ a :- not b. /* a if b fails*/ a :- b -> c;d. /* a if (if b then c else d)*/


Execution Control

Execution

Top to bottom

Left to right


Write predicate

test:-

write (“This is an example”),

write(“of multiple write statements.”).

Displays:

This is an example of multiple write statements.


Output predicates

Three output predicates: 1. write

2. writedevice

3. writef


The write predicate

go :-

hypothesis(Patient,Disease),

write(Patient,” probably has “,Disease,”.”) ,nl.

New lineAnother method \n

Go will unify with the

Conclusion of new rule

Unify with conclusion of your new rule


Writef Predicate

Used to force alignment of numbers or text Format:

writef(format,E1,E2,…,En)

ex. writef(“%-10#5.0$%3.2\n”,fan,23,3.1)

displays

fan #23$3.10


Input predicates

readln : string or symbol readchar : character readint : integer readreal : real


readchar Predicate Symptom(patient,feve

r):-

write(“Does the “,patient,” have a fever(y/n)?”),

readchar(Reply),nl

Reply=‘y’.

Symptom(patient,fever):-

write(“Does the “,patient,” have a fever(yes/no)?”),

readln(Reply)

Reply=“yes”.

ReadlnPredicate


readintPredicate Write(“what

is”,patient,” ’s age?”).

readint(Age),

Age>=12,

Write(Patient,”cannot be evaluated with”),nl

Write(“this system.”).

Write(“what is the real price of ”,Item,”?”),

readreal(Price).

readrealPredicate


Applications of Prolog

Prolog is used in applications that requires formal reasoning.

Basic Applications: Expert System Natural Language Processing Robotics Gaming and Simulation


Natural Language Processing Using Prolog, knowledge about human language

is expressed in formal rules and facts. The computer can then begin a dialog with the

user, asking questions about the problem and interpreting the user’s answer.


Robotics

Robotics is a branch of artificial intelligence concerned with enabling computers to see and manipulate objects in their environment.

Prolog facilitates the development of robotic control programs that can use input data from sensors to control manipulators.

A robot can then apply formal reasoning to decisions, much as a human being does.


Gaming and Simulation

Prolog is ideal for games and simulations (cognitive modeling) involving formal reasoning.

Most games and simulation employ a set of logical rules that control the play or action which is very adaptable to Prolog programming.

Classical game such as

N Queen Problem is written in Prolog.


Expert system

Expert system are programs that use inference techniques that involves formal reasoning normally performed by a human expert to solve problems in specific area of knowledge.

Each expert system can advise, diagnose, analyze and categorize using a previously defined knowledge base.

The knowledge base is a collection of rule and facts which can be written in Prolog.


Prolog shines in two major areas: search Pattern Matching


Building an Expert System

Defining the goal and domain Getting the facts Charting the facts Clustering Writing the program Testing the program


Disadvantages

Very inefficient If trying to use it for numerical or string processing involving known procedures.

Does not support virtual memory


Documents

Turbo Prolog 173 ACR