lecture03

Knowledge Representationin

Digital HumanitiesAntonio Jiménez Mavillard

Department of Modern Languages and LiteraturesWestern University

Lecture 3

Knowledge Representation in Digital HumanitiesAntonio Jiménez Mavillard

* Contents: 1. Why this lecture? 2. Discussion 3. Chapter 3 4. Assignment 5. Bibliography

2

Why this lecture?


* This lecture... · trains the problem solving skill by means of algorithm formalization · prepares the ground to write real programs

3

Last assignment discussion


* Time to... · consolidate ideas and concepts dealt in the readings · discuss issues arised in the specific solutions to the projects

4

Chapter 3

Fundamentals of Programming

1. Designing algorithms2. Elements of a program

Knowledge Representation in Digital HumanitiesAntonio Jiménez Mavillard5

Chapter 3

1 Designing algorithms 1.1 The programming process 1.2 What is an algorithm?


Chapter 3

2 Elements of a program 2.1 What is a program? 2.2 Components of a program 2.3 Types of errors


Designing algorithms


The programming process

* Programming cycle: 1. Define the problem 2. Plan the solution 3. Code the program 4. Test the program 5. Document the process



* Define the problem · Identify the input data (what we have) · Determine the output information (what we want to obtain)



* Plan the solution · Design an algorithm + by drawing a flow diagram + by writing pseudocode



* Code the program · Translate the algorithm into a programming language



* Test the program · Verify if for certain input, the program produces the correct output · Find and fix errors (debugging): + syntax + runtime + semantic



* Document the process · Describe the problem and the solution · Include pseudocode or flow diagrams · Report testing results · Comment the code


References

Glassborow, Francis. “Chapter 1: You Can Program.” You Can Do It!: A Beginner’s Introduction to Computer

Programming. Chichester, West Sussex, England; Hoboken, NJ: John Wiley, 2004. Print.

Mohd Harris. “PROG0101 - Fundamentals of Programming.” N. p., n.d. Web. 17 Jan. 2014.

Perry, Greg M. “Chapter 2: Anatomy of a Program.” Absolute Beginner’s Guide to Programming. Indianapolis, Ind.: Que

Pub., 2003. Print.


What is an algorithm?

* Definitions · A detailed plan to solve a problem · A step-by-step set of instructions for solving a problem · A finite process that if followed will solve a problem



* Characterized by 5 properties: 1. Input: initial data 2. Output: final result



* Characterized by 5 properties: 3. Finiteness: has to terminate in a finite number of steps 4. Definiteness: each step has to be unambiguously specified 5. Effectiveness: each step should be doable in a finite time by a human



* Exercise 1 · A recipe is an algorithm that solve the next problem: how to prepare a meal · Search for the recipe of Green Tea Berry Delight (http://allrecipes.com/Recipe/Green-Tea-Berry-Delight/Detail.aspx)


http://allrecipes.com/Recipe/Green-Tea-Berry-Delight/Detail.aspx


* Exercise 1 · Identify: input, output and steps · Answer the following questions: + Is the recipe finite? + Is each step definite? + Is each step effective?


What is an algorithm?* Exercise 1 (solution) · Recipe:


What is an algorithm?* Exercise 1 (solution) · Is the recipe finite? Yes, it is done in 5 minutes · Is each step definite? Yes, they are not ambiguous · Is each step effective? Yes, in fact they are thought to be done by a human



* Exercise 2 · Design an algorithm to divide two numbers by using only additions and substractions



* Exercise 2 (solution) · Solve the specific case: divide 7 by 3 Hint: how many times is 3 contained in 7? · Solve the general case: divide A by B



* Exercise 2 (solution) · How many times is 3 contained in 7?



* Exercise 2 (solution) · Count the number of sustractions


What is an algorithm?* Exercise 2 (solution)


What is an algorithm?* Exercise 2 (solution) Is the algorithm correct? Trace for 7/3


Step 0 A is 7, B is 3, C is 0Step 1 Is 7 >= 3? Yes A is now 7 3 = 4 C is now 0 + 1 = 1Step 2 Is 4 >= 3? Yes A is now 4 3 = 1 C is now 1 + 1 = 2Step 3 Is 1 >= 3? NoStep 4 Output C, that is 2

References

Cormen, Thomas H. “Chapter 1: The Role of Algorithms in Computing.” Introduction to Algorithms. Cambridge,

Masachusetts; London: The MIT Press, 2009. Print.

De la Rosa, Javier. “Computer Tools for Linguists.” Yutzu. N. p., n.d. Web. 16 Sept. 2013.

Knuth, Donald E. “Chapter 1: Basic Concepts.” The Art of Computer Programming. Volume 1: Fundamental Algorithms.

Vol. 1. Reading, Mass.: Addison-Wesley, 1997. Print.


Elements of a program


What is a program?

* Definition “A program is an implementation of an algorithm in a program language.” (The concrete written program is called source code or just code)


What is a program?

* Algorithm vs program · Algorithm: + Abstract + Represented by a flow diagram, pseudocode... + For human understanding


What is a program?

* Algorithm vs program · Program: + Concrete + Represented by a program language + For computer processing


Components of a program

* The content and structure of a program depend on the programming language* Every programming language is formed by a set of symbols* The combination of these symbols defines the programs



* Programming languages are defined by: · Morphology · Syntax · Semantics



* Morphology · Symbols: numbers, letters and special characters · Symbols are combined to form tokens: the basic elements of a language



* Morphology · Vocabulary: a set of keywords (special tokens) with specific funcionality · Examples in Python: def, elif, except, print



* Syntax · Grammar rules to write a program + Tokens - How the symbols are combined - Examples in Python: correct: 3, counter, def incorrect: $+1, (&variable


Components of a program* Syntax · Grammar rules to write a program + Structure - Way that tokens are arranged - Expressions, blocks... - Examples in Python correct: a += 1 incorrect: a $= 1


Components of a program* Semantics · Meaning of the program · Examples: how to interpret the order of the operators + Operator precedence x - 2 * 3 ≡ x - (2 * 3) + Operator associativity x - 2 + 3 ≡ (x - 2) + 3



* A program is a set of instructions* An instruction is an statement* A statement is an executable unit of code formed by expressions* An expression is a combination of tokens* A token is a sequence of symbols



* Exercise 3 Given the next code...


fruit = 'banana'counter = 0index = 0while index < len(fruit): char = fruit[index] if char == 'a': counter += 1 index += 1print counter


* Exercise 3 ... identify: · Symbols, tokens and keywords · Some grammar rules · Its semantics



* Exercise 3 (solution) · symbols: letters, numbers, ', <, (, ), :, =, [, ], and + · tokens: fruit, =, 'banana', counter, 0, index, while, <, len(fruit), :, char, fruit[index], if, ==, 'a', +=, 1, print · keywords: while, len, if, print


Components of a program* Exercise 3 (solution) · grammar rules: quotations for strings '', colon after testings :, indentention for blocks, closing parenthesis after opening parenthesis (), closing bracket after opening bracket [] · semantics: counts and print on screen number of a's in the word “banana”


References


The Little Introduction To Programming. N. p. Web.


Types of errors* Syntax error The code of the program breaks the syntax rules of the programming language* Logic error The code is syntactically correct but results in illegal operations in execution* Semantic error The program does not behave as expected


Types of errors* Examples in Python · Syntax error a + 1 = b Assignment malformed · Logic error a = 4 b = 0 c = a / b Division by 0


my_list = [1, 2, 3, 4] element = my_list[7]Access to a non existing object

Types of errors* Examples in Python · Semantic error

It does not print the number of a'sKnowledge Representation in Digital Humanities

Antonio Jiménez Mavillard50

fruit = 'banana'counter = 0index = 0while index < len(fruit): char = fruit[index] if char == 'a': counter += 1 index += 1print fruit

References

Severance, Dr Charles R. “Chapter 1: Why Should You Learn to Write Programs?” Python for Informatics: Exploring

Information. 1 edition. CreateSpace Independent Publishing Platform, 2013. Print.


Assignment

* Assignment 3: Playing with algorithms · Readings + The Role of Algorithms in Computing (Introduction to Algorithms) + Strings (Python for Informatics)


Assignment* Assignment 3: Playing with algorithms · Project + Write an algorithm in Python that cleans a text of punctuations marks


O Romeo Romeo wherefore art thou Romeo Deny thy father and refuse thy name Or if thou wilt not be but sworn my love And I'll no longer be a Capulet

O Romeo, Romeo! wherefore art thou Romeo? Deny thy father and refuse thy name; Or, if thou wilt not, be but sworn my love, And I'll no longer be a Capulet.

»

References

Cormen, Thomas H. “Chapter 1: The Role of Algorithms in Computing.” Introduction to Algorithms. Cambridge,

Masachusetts; London: The MIT Press, 2009. Print.

Severance, Dr Charles R. “Chapter 6: Strings” Python for Informatics: Exploring Information. 1 edition. CreateSpace

Independent Publishing Platform, 2013. Print.


BibliographyCormen, Thomas H. Introduction to Algorithms. Cambridge, Masachusetts; London: The MIT Press, 2009. Print.


Glassborow, Francis. You Can Do It!: A Beginner’s Introduction to Computer Programming. Chichester, West Sussex,

England; Hoboken, NJ: John Wiley, 2004. Print.

Knuth, Donald E. The Art of Computer Programming. Volume 1: Fundamental Algorithms. Vol. 1. Reading, Mass.:

Addison-Wesley, 1997. Print.

Mohd Harris. “PROG0101 - Fundamentals of Programming.” N. p., n.d. Web. 17 Jan. 2014.

Perry, Greg M. Absolute Beginner’s Guide to Programming. Indianapolis, Ind.: Que Pub., 2003. Print.

Severance, Dr Charles R. Python for Informatics: Exploring Information. 1 edition. CreateSpace Independent Publishing

Platform, 2013. Print.

The Little Introduction To Programming. N. p. Print.


lecture03

Technology

human knowledge representation

programming process

algorithm formalization

finite process

fundamentals of programming

computer programming

programming cycle

solution recipe