2 Prolog L 1 V2.ppt
- 1. 11/18/2023 1 Artificial Intelligent Dr Ahmed Al-Arashi December 2017 PROLOG
- 2. 11/18/2023 2 Introduction Early 1970 in Marseilles, formed by Alain Colmerauer. In 1981 Japanese choose Prolog for the fifth generation computers. PROLOG (PROgraming in LOGic) is widely used in Europe. Programing LISP (LISt Processing). Various Prolog compilers/programing environment are available. PDC prolog (previously turbo prolog) is typed.
- 3. 11/18/2023 3 Prolog Against Other Programing Languages Languages such as C, Fortran and Basic are procedural languages and use algorithms. Prolog manipulates the data according to defined procedures. It uses heuristics solve problems. Prolog program is a collection of facts and relationship. It uses no procedures to solve a problem, it uses data about objects and relationship to solve the problems. The user defines the goal and the program find the procedures and solution. Prolog is not efficient at numerical processing but it is most efficient at reasoning. Prolog is good at inferring facts from given facts.
- 4. 11/18/2023 4 Applications of Prolog It is most useful at AI programing. Application includes: Expert Systems. Natural Language Processing. Robotics. Gamming.
- 5. 11/18/2023 5 PDC Prolog Stand alone programs. Some standard predicates. Interface with other programing languages. Arithmetic operations can be programed. It has good working environment. Main windows includes: – Editor. – Dialog. – Message. – Trace.
- 6. 11/18/2023 6 PDC Objects Most important PDDC Prolog objects include: char: Single character written between quartinos. Example ‘a’, ‘y’ and ‘n’. integer: integers of range (-37,368 to 32,767). real: floating point number range (e-307 to e308 ) string: character sequences double written between quartinos. Example “abc”, “SDF” and “aBc”. symbol: character sequences of letters, numbers and under scores. The first character must be small character. Examples ali_hassan, page_1, cARS and city_Sanaa
- 7. 11/18/2023 7 PDC Basic Sections (1/2) PDC prolog program are divided into number of sections. Basic ones will be discussed now, and others will be introduced in the lap. and/or in the coming lectures. Below are most basic ones: Domains: All objects type are defined in this section. In this Domains Examples person, item = symbol price = real replay = char
- 8. 11/18/2023 8 PDC Basic Sections (2/2) Predicates: In this section all facts and relevant objects are defined except few built-in predicates. Predicates Examples own(person ,item) like(person, food, type) Built-in Predicates Examples save(string) write(arg_1, arg_2, arg_3) Clauses: Main PDC prolog program is written in this section. It can include one or more fact/rule. All the facts that are in the clauses section must be defined first in domains and/or predicates sections in terms of relation name, arguments number and type.
- 9. 11/18/2023 9 Variables Objects in prolog can be given a variable name. Variable names is a sequence of , numbers and under scores. The first letter must be Capital letter. Examples Name Price City_1, Variables is usually used in clauses section and may be used in goal. They get their type from the predicates.
- 10. 11/18/2023 10 How Variables Gets their Values Variables gets their values by being matched to constants in facts and/or rules. When a variable gets a value it said to be bound. When it is not bound it is said to be free. It is important to not that, in prolog, variables for only the time needed to obtain one solution. For this reason we can not store information by giving a value to a variable as we normally do in other programming languages. Anonymous Variables Anonymous variable is a variable that is used in place of any other variable with unknown value. It is represented by underscore “_”
- 11. 11/18/2023 11 Prolog Goals (Queries) To asking prolog a question we use goal section as follows: goal predicate. When asking prolog a question it tries to find answer. In other words when prolog is given a query it means that it is given a goal to accomplish. Goals can be single or compound. Single goal is when asking one question using one predicates only. Lets start with making single goal clear through an example.
- 12. 11/18/2023 12 Example domains name, item =symbol predicates owns(name,item) clauses owns(ahmed,car). owns(ahmed,house). owns(ali,book). owns(ali,pen). owns(salma,car). owns(salma,shose). owns(hassan,pen). owns(hassan,car). Lets ask who owns pen?: goal owns(Person,pen). Prolog responds: Person = ali Person = hassan 2 solutions Lets tray owns(_,car). What does this means? Prolog responds: true (yes).
- 13. 11/18/2023 13 Compound Goals Compound goal it means that prolog is asked to answer more than one query. Tow types of compound goals are used in prolog conjunction an disjunction. Conjunction goal: When is set of facts separated by comma (,) which means and. Example owns(Person, pen), owns(Person, car). This means is their a Person who owns pen and car. Disjunction goals When set of facts separated by semicolon (;) which means or. Example owns(Person, pen) ; owns(Person, car). This means is their a Person who owns pen or a Person who owns car
- 14. 11/18/2023 14 Prolog Rules Prolog rules consists of two parts, head and body. It takes the form of (if then), but differ totally than what is used in other conventional programming languages. The head is a conclusion that can be drawn provided that all the facts in the body are proven to be true. As an example look at the following expression: This is a square if: - It is a closed shape. - It has four sides. - All sides are equal. - every side is perpendicular on the other tow sides.
- 15. 11/18/2023 15 Prolog Rules In Prolog, the previous example can be written as follows: this_is(square):- shape(closed), - no_of_sides(4), - all_sides(equal), - relation_with other_sides(perpendicular)
- 16. 11/18/2023 16 Internal Goals domains name = symbol predicates father(name,name) everybody clauses father(khaled, somia). father(hassan, sami). father(hassan, maryam). everybody:- father(X,Y), write(X "is ", Y,"'s fathern"). goal everybody.
- 17. 11/18/2023 17 Medical Example See the word file