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2018

LOGIC PROGRAMMING. By Dr. Metwally Rashad. 2018. Course Specification and Aim. Course Data - Course Code : CSW352 - Specialization: Computer Science - No. of Instructional Units: Lecture 3 hrs/week Practical 2 hrs/week 5 hrs/week. Course Aim

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2018

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  1. LOGIC PROGRAMMING By Dr. Metwally Rashad 2018

  2. Course Specification and Aim • Course Data • - Course Code: CSW352 • - Specialization: Computer Science • - No. of Instructional Units: Lecture 3 hrs/week Practical 2 hrs/week5 hrs/week • Course Aim • - The course is intended to give the student an understanding of the principles of logic • programming and how these are applied to standard problems in AI. 1/29

  3. Schedule Assessment 1 Week 4 Midterm exam Week 7 or 8 Assessment 2 Week 11 Oral exam Week 14 Practical exam Week 15 Final exam Week 16 2/29

  4. Weighting of Assessment: Mid-Term Examination 10 % Final-term Examination 65 % Oral Examination 10 % Practical exam 15 % --------------------------------------------------------------------- Total 100 % 5 3-Quiz 10 P. Exam 3/29

  5. Course Materials • Ivan Bratko, Prolog Programming for Artificial Intelligence, (4ED), • Pearson Education Limited, 2012, ISBN 978-0-231-41746-6. • Ulf Nilsson and Jan Ma luszynski, Logic, Programming and Prolog (2ED). • Patrick Blackburn, Johan Bos, Kristina Striegnitz, Learn Prolog Now!. 4/29

  6. Contents • Introduction and Logic Foundations of Prolog • Prolog Variables, Bound and free Variables and Matching • Syntax and Meaning of Prolog Program • Backtracking and Recursive Rule Definition • Built-in Predicates and Arithmetic Expressions • Lists Manipulation I • Lists Manipulation II • Operators • Controlling Backtracking I • Controlling Backtracking II • Data Structures in Prolog • Advanced Techniques 5/29

  7. Logic programming • Programming languages are of two kinds: • - Procedural (BASIC, ForTran, Pascal ,C++, Java). • - Declarative (LISP, Prolog, ML). • In procedural programming, we tell the computer how to solve a problem. • In declarative programming, we tell the computer what problem we want solved. • (you do not write out what the computer should do line by line) • The general idea behind declarative languages is that you describe a situation. • - Based on this code, the interpreter or compiler will tell you a solution. 6/29

  8. History of Logic Programming (LP) • Formulated in 1974 by a professor at Univ. of Edinburgh. • First system implemented in 1995 by a research group in France. • First compiler built in 1997 by a PhD student also in Edinburgh. • Japan’s fifth generation computer project announced in 1980. • Efficiency improved in recent years. • Interfaces with other languages such as C/Java. 7/29

  9. Why Prolog is not as popular as C/Java? • Mistaken at first as some universal computer language. • Not yet as efficient as C. • Support to Prolog takes effort, resources; companies are not willing • to pay for it. • Its value not recognized by industry. 8/29

  10. What is a logic? A logic is a language: it has syntax and semantics. More than a language, it has inference rules. Syntax: the rules about how to form formulas; this is usually the easy part of a logic. Semantics:about the meaning carried by the formulas, mainly in terms of logical consequences. Inference rules: describe correct ways to derive conclusions. 9/29

  11. Prolog • “Programming with Logic“ • Very different from other (procedural) programming languages. • Good for knowledge-rich tasks. • Prolog is a computer programming language that is used for solving • problems that involve objects and the relationships between objects. • In Prolog, the word "object" does not refer to a data structure that can • inherit variables and methods from a class, but it refers to things that • we can represent usingterms. • A Prolog program consists of clauses. Each clause terminates with a full stop. 10/29

  12. History of Prolog first Prolog interpreter by Colmerauer and Roussel 11/29 1972 1980s/1990s 1977 1980 2005

  13. History of Prolog implementation of DEC10 compiler by Warren 12/29 1972 1980s/1990s 1977 1980 2005

  14. History of Prolog Definite Clause Grammars implementation by Pereira and Warren 13/29 1972 1980s/1990s 1977 1980 2005

  15. History of Prolog Prolog grows in popularity especially in Europe and Japan 14/29 1972 1980s/1990s 1977 1980 2005

  16. History of Prolog Prolog used to program natural language interface in international space station by NASA 15/29 1972 1980s/1990s 1977 1980 2005

  17. Basic idea of Prolog • Describe the situation of interest. • Ask a question. • Prolog logically deduces new facts about the situation we • described. • Prolog gives us its deductions back as answers . 16/29

  18. Logic Formulas • When describing some states in the real world, we often use declarative • sentences like: • - Every mother loves her children • - Mary is a mother and • - Tom is Mary's child • By applying some general rules of reasoning such descriptions can be used to • draw new conclusions. • - Mary loves Tom 17/29

  19. Logic Formulas • Declarative statement contains: • Persons (individual) • "Mary, Tom". • - Relation between individuals like: • ".. . is a mother " • ". . . is a child of . . . " • ". . . loves . . . " • - Relation may not hold between individuals like: • "…being a mother" • - Relations with more than two objects like: • ". . . is the sum of . . . and . . . " 18/29

  20. Concept of Logic Formulas • Constant: • - Symbols for denoting individuals • Tom  tom • Predicate (functor): • - Symbols for denoting relations • (loves , mother, child of ) • Arity: • - Number of arguments of the predicate. • loves  2-ary • - nullary 0-ary, unary 1-ary, binary  2-ary and ternary 3-ary. 19/29

  21. Formalization • The formal language should provide sentences refers to all elements of the • described “world". • - e.g. • “for all individuals X and Y, if X is a mother and Y is a child of X then X loves Y". • The language of logic introduces: • -“” symbol of universal quantifier • To be read “for every“ or “for all“ • -Variableis a symbol that refers to an unspecified individual, • like X and Y 20/29

  22. Formalization • Previous example can be formalized • “" reads “and" • “, " is called implication and corresponds to the “if-then“ • (….) are used to disambiguate the language. ⇒ 21/29

  23. Formalization • “” denoted by negation (with reading “not") • “Tom does not loves Mary"   loves(tom, mary) • “” denoted by existential quantifier and reads “there exists". • - The existential quantifier makes it possible to express the fact . • - There exists at least one individual which is in a certain relation with some other • individuals. • - “Mary has a child"  X child of (X, mary). • “”  OR • “”  “if and only if” • Compound term • family(bill, mary, child (tom, child (alice, none))) 22/29

  24. Examples 1. All cats are mammals 2. All of Bill’s kids are also Hillary’s kids 3. Somebody likes brain 4. Nobody likes brain - ∀X(cat(X)⇒mammal(X)) - ∀X(father(bill, X)⇒mother(hillary, X)) - ∃X(likes(X, brain)) - ¬ ∃X[likes(X, brain)] or ∀X[¬ X(like(X, brain)) which is mean everybody doesn't likes brain 23/29

  25. Try with your self 1. marcus was a man 2. All pompeians were romans 3. caesar was a ruler. 4. All romans were either loyal to caesar or hated him. 5. Everyone is loyal to someone. 6. marcus tried to assassinate caesar 24/29

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