Some Well-known Computer Scientists

Some Well-known Computer Scientists

• 1.
  Some Well-known Computer Scientists Yann-Gaël Guéhéneuc Départementde génie informatique et de génie logiciel This work is licensed under a Creative Commons Attribution-NonCommercial- ShareAlike 3.0 Unported License yann-gael.gueheneuc@polytmtl.ca Version 1.0 2013/04/22
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  Any questions/comments arewelcome at 2/76 Any questions/comments are welcome at yann-gael.gueheneuc@polymtl.ca
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  Why Is ItImportant? (1/2) “Those who cannot remember the past are condemned to repeat it” 3/76 —By George Santayana in Life of Reason, Reason in Common Sense, Scribner's, 1905, page 284
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  Why Is ItImportant? (2/2) Pythagoras’ theorem Ohm’s law … 4/76 … You know the Nobel Prizes… … do you know the Turing Awards?
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  How to Choose?(1/2) Hundreds of women and men made and are making the history of computer science – Difficult choice, impossible choice 5/76 – Inclusion criteria • Historical importance • Historical continuity • Link to software engineering – No exclusion criteria!
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  How to Choose?(2/2) Suggestions for other computer scientists to appear here – Please send an e-mail to Yann-Gaël Guéhéneuc 6/76 yann-gael.gueheneuc@polymtl.ca
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  Some Well-known ComputerScientists 1936 Alan Turing 1948 Claude Elwood Shannon 1950 Grace Murray Hopper 1960 John McCarthy 1966 Frances E. Allen 1972 Dave Parnas 1974 Manny Lehman 1975 Frederick Brooks 1986 Edward Yourdon 1987 Barbara Liskov 7/76 1966 Frances E. Allen 1967 Dahl et Nygaard 1969 Charles A. R. Hoare 1970 Edgar F. Codd 1987 Barbara Liskov 1994 Erich Gamma 1997 Grady Booch
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  Alan Turing Alan MathisonTuring – Born June 23rd, 1912, died June 7th, 1954 – Turing machines, undecidability, halting problem, computability Alan Turing *1912 †1954 8/76 problem, computability The Turing Award is given in his honour IEEE Milestone … – http://en.wikipedia.org/wiki/Alan_Turing
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  Alan Turing 1928 – Hilbertintroduced the decision problem 9/76 1931 – Gödel give results on the limits of proofs and computability
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  Alan Turing 1936 – Turingintroduce a concept of machines now known as “Turing machines” – Turing prove with his machines that the halting 10/76 – Turing prove with his machines that the halting problem is undecidable
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  Alan Turing Halting problem –First problem proven undecidable – Used to prove that other problems are undecidable by reduction 11/76 undecidable by reduction
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  Alan Turing Generalisation ≠particular cases – Correctness proofs are posibles but on particular problems and not automatically in the general case 12/76 general case Formal methods ≠ tests – Prove the correctness of a particular algorithm – Prove the presence of errors
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  Alan Turing 1938−1945 – Workat Bletchley Park • British Government Code and Cypher School • Five major contributions 13/76 • Five major contributions – Decode the Enigma code of the German army – Decode the indicator procedure of the Enigma use by the German navy – Develop a statistical method to make the “Bombe” more efficient – Develop a procedure to decode the Lorenz SZ 40/42 machines – Develop a voice scrambler
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  Alan Turing 1952 – Turingtest 1966 – ELIZA Joseph Weizenbaum *1923 †12008 14/76
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  Claude Elwood Shannon ClaudeElwood Shannon – Born April 30th, 1916, died February 24th, 2001 – Father of the information theory Claude Elwood Shannon *1916 †12001 15/76 – Father of the information theory National Medal of Science in the USA in 1966 IEEE Medal of Honor in 1966 … – en.wikipedia.org/wiki/Claude_Shannon
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  Claude Elwood Shannon 1830s –Telegraph – Morse Code 16/76
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  Claude Elwood Shannon 1830s –A form of lossless compression 17/76
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  Claude Elwood Shannon 1948 «The fundamental problem of communication is that of reproducing at one point, either exactly or 18/76 that of reproducing at one point, either exactly or approximately, a message selected at another point. » —Shannon, in A Mathematical Theory of Communication, 1948
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  Claude Elwood Shannon 1948 –Probabilistic theory quantifying the average information content of a message 19/76 – Entropy – Code theory • Compression • Detection et correction of errors – All electronic “communication”! – Cryptography
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  Grace Murray Hopper GraceMurray Hopper (rear admiral) – Born the 9th of December, 1906, died the 1st of January, 1992 – Mother of the first compiler, of the term Grace Hopper *1906 †1992 20/76 – Mother of the first compiler, of the term “debugging”, of COBOL and of standards Defense Distinguished Service Medal in the USA in 1986 – Cf. http://en.wikipedia.org/wiki/Grace_Hopper
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  Grace Murray Hopper 1944 –WWII is almost over – Computers showed their usefulness 21/76 • Dehomag D11 (Germany/USA, 1930s): handling of identify cards • Zuse Z3 (Germany, 1941): flutter (dynamic aeroelasticity of wings) • Colossus Mark 1 (Grande Bretagne, 1943): decoding of messages • Harvard Mark I (USA, 1944): production of calculus tables for the Navy
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  Grace Murray Hopper Principleof the first computers – Electromechanical or electromagnetic relays 22/76 electromagnetic relays – Two active relays make a third relay active • Relays “3” et “6” make relay “9” active for a sum 1947
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  Grace Murray Hopper 1950 –Computers become programmable with higher- level languages than microcode or assembly • UNIVAC I: census 23/76 • UNIVAC I: census • A-0 (Arithmetic Language version 0) • Loader or linker more than a compiler 1954 – B-0 (Business Language version 0) also known as FLOW-MATIC
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  Grace Murray Hopper 1959 –Conference CODASYL (Conference on Data Systems Languages) – COBOL as successor of FLOW-MATIC 24/76 – COBOL as successor of FLOW-MATIC – Close to English 1970s – Advocated standards tests for programming languages, FORTRAN in particular
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  John McCarthy John McCarthy –Born the 4th of September, 1927 – Died on the 24 October, 2011 – Father of artificial intelligence, LISP, contributor to time- John McCarthy *1927 †2011 25/76 – Father of artificial intelligence, LISP, contributor to time- sharing computing, inventor of “SaaS” ACM Turing Award in 1971 National Medal of Science in the USA in 1991 – Cf. http://en.wikipedia.org/wiki/John_McCarthy_(computer_scientist)
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  John McCarthy Artificial intelligence,1956 – Champion of logic programming – Collaboration with Marvin Minsky 26/76 Inventor of LISP, 1960 – Recursive Functions of Symbolic Expressions and Their Computation by Machine, Part I, 1960 – Lambda calculus – Garbage collection
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  John McCarthy Time-sharing systems –Multiprogramming and multitasking – Most important change of paradigm in computer science in 1970 DEC PDP-1, c. 1960 27/76 science in 1970 • Sharing of resources to avoid “waiting computation time (cycles)” – SaaS • Software as a Service • Architecture/engineering based on services
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  Frances E. Allen FrancesE. Allen – Born on the 4th of August, 1932 – Pioneer of optimising compilation, code optimisation, and parallelisation Frances E. Allen *1932 28/76 optimisation, and parallelisation AWC Augusta Ada Lovelace Award en 2002 ACM Turing Award en 2006 – Cf. http://en.wikipedia.org/wiki/Frances_E._Allen
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  Frances E. Allen Before1966 – Since the 1930s • Programmable computers – Since the 1950s 29/76 – Since the 1950s • First compilers by Grace Murray Hopper • Programming languages – FORTRAN: first complete compiler – COBOL: first programming language compiled for different computer architectures (UNIVAC II et RCA 501)
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  Frances E. Allen Before1966 – In 1955 • Context-free grammar invented by Noam Chomsky – In 1966 30/76 – In 1966 • LR Parsing invented by Donald Knuth
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  Frances E. Allen In1966 – Program Optimization • Use of graphs to describe programs and to allow their optimisations 31/76 In 1970 – Control Flow Analysis et A Basis for Program Optimization • Intervals for control-flow analyses In 1974 – Interprocedural data flow analysis • Interprocedural analyses of whole programs
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  Dahl–Nygaard Ole-Johan Dahl – Born12 October 1931, †29 June 2002 – Co-inventor of the object-oriented paradigm Ole-Johan Dahl *1931 †2002 32/76 – ACM Turing Award in 2001 – IEEE J. von Neumann in 2002 – Cf. http://www.olejohandahl.info/ – Cf. http://en.wikipedia.org/wiki/Ole-Johan_Dahl
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  Dahl–Nygaard Kristen Nygaard – Born27 August 1926, †10 August 2002 – Co-inventor of the object-oriented paradigm Kristen Nygaard *1926 †2002 33/76 – ACM Turing Award in 2001 – IEEE J. von Neumann in 2002 – Cf. http://www.ifi.uio.no/in_memoriam_kristen/ – Cf. http://en.wikipedia.org/wiki/Kristen_Nygaard
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  Dahl–Nygaard Object-oriented paradigm – Context •1961 – Algol imperative programming 34/76 – Algol imperative programming – Classes, objects, encapsulation, inheritance, polymorphism • Simula I • Simula 67
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  Dahl–Nygaard Object-oriented programming – Smalltalk •Xerox Parc, 1970–1983 – GUI 35/76 – GUI – Icons – WYSIWYG – Mouse (cf. Stanford Research Institute) • Dynamic typing • Reflection • Garbage collection
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  Dahl–Nygaard Object-oriented programming – C++ •AT&T Bell Labs • Bjarne Stroustrup 36/76 • Bjarne Stroustrup • 1980 • Static typing • Multiple inheritance • Cf. http://www.approximity.com/ruby/ Comparison_rb_st_m_java.html
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  Dahl–Nygaard Object-oriented programming – Oberon •ETH Zurich • Niklaus Wirth 37/76 • Niklaus Wirth • 1986 • Static typing • Garbage collection • Array bounds checking
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  Charles A. R.Hoare Sir Charles Antony Richard Hoare – Born January 11th, 1934 – Inventor of QuickSort Sir Charles Antony Richard Hoare *1934 38/76 – Inventor of the Hoare logic – – ACM Turing Award in 1980 – IEEE J. von Neumann in 2011 – Cf. http://en.wikipedia.org/wiki/C._A._R._Hoare
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  Charles A. R.Hoare QuickSort – Context • 1960 – In Soviet Union, Hoare works at Moscow State University in 39/76 – In Soviet Union, Hoare works at Moscow State University in automatic translation – He must sort words to be translated to map them with words already translated – QuickSort • O(n × log(n)) in average, O(n2) worst case • Works well with a cache
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  Charles A. R.Hoare Hoare logic – Context • 1969 – Study program correctness 40/76 – Study program correctness – Original idea sown by Robert Floyd in 1967 – Verification of the correctness of a program • Hoare triplet: {P} C {Q} • Pre-condition P, instruction C, post-condition Q • Set of rules for imperative languages…
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  Edgar F. Codd EdgarFrank “Ted” Codd – Born August 23rd, 1913, died April 18th, 2003 – Father of relational algebra Edgar F. Codd *1923 †12003 41/76 – Father of relational algebra ACM Turing Award en 1999 – http://en.wikipedia.org/wiki/Edgar_F._Codd
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  Edgar F. Codd 1960s –Databases become possible • Direct-access storages – No standard data models or query models 42/76 – No standard data models or query models – Two dominant models • CODASYL, network model – “Manual” traversal • IBM/IMS, hierarchical model – Relations 1:n only (Microsoft Windows Registry)
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  Edgar F. Codd 1970 –“A Relational Model of Data for Large Shared Data Banks” • Limits of the CODASYL approach Lawrence Joseph "Larry" Ellison *1944 43/76 • Limits of the CODASYL approach • Introduction of the concept of tables • Introduction of the concept of relation (keys) – IBM Future Systems includes SEQUEL in 1975 – Relational Software Inc. release Oracle in 1979 (SEQUEL becomes SQL at the end of the ’70s)
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  Edgar F. Codd Today –SQL is a standard • ANSI since 1986 • ISO since 1987 44/76 • ISO since 1987 – Implemented by almost all existing databases – Interoperability • Careful with proprietary extensions • Careful with ambiguities
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  Edgar F. Codd 45/76
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  Edgar F. Codd NoSQL –http://nosql-database.org/ – http://www.10gen.com/nosql 46/76
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  Dave Parnas Dave Parnas –Born February 10th, 1941 – Father of the criteria to divide a program into modules in a modular design Dave Parnas *1941 47/76 modules in a modular design IEEE Computer Society 60th Anniversary Award in 2007 – Cf. http://en.wikipedia.org/wiki/David_Parnas
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  Dave Parnas Modular design –Context • 1972 – Procedural and object 48/76 – Procedural and object programming languages – Flow diagrams – Decomposition of programs in modules, classes…
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  Dave Parnas – Criteria •“[I]t is almost always incorrect to begin the decomposition of a system into modules on the basis of a flowchart. We propose instead that one begins 49/76 of a flowchart. We propose instead that one begins with a list of difficult design decisions or design decisions which are likely to change. Each module is then designed to hide such a decision from the others” • Information hiding = Encapsulation
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  Dave Parnas – Rewritingof the criteria in terms of • Cohesion • Coupling 50/76 • Concepts “invented” by Larry Constantine in 1968 and published in 1972 in W. Stevens, G. Myers, L. Constantine, "Structured Design", IBM Systems Journal, 13 (2), 115-139, 1974. • A module must have a strong cohesion and be weakly coupled to other modules
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  Manny Lehman Meir M.“Manny” Lehman – Died December 29th, 2010 – Father of the laws of software evolution Manny Lehman *1925 †2010 51/76 Stevens Award in 2003 – Cf. http://www.doc.ic.ac.uk/news/archive/story/ manny-lehman – Cf. http://www.ieeeghn.org/wiki/index.php/Oral- History:Meir_Lehman
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  Manny Lehman Laws ofsoftware evolution – Context • 1974 – IBM OS/360 et OS/370 52/76 – IBM OS/360 et OS/370 • Types of programs – S: can be formally specified – P: follow an iterative development process – E: are embedded in our environment
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  Manny Lehman – Eightlaws 1. Continuing change: E-type systems must be continually adapted or they become progressively less satisfactory 2. Increasing complexity: As an E-type system evolves its complexity increases unless work is done to maintain or 53/76 complexity increases unless work is done to maintain or reduce it 3. Self regulation: E-type system evolution process is self regulating with distribution of product and process measures close to normal 4. Conservation of organisational stability: The average effective global activity rate in an evolving E-type system is invariant over product lifetime
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  Manny Lehman – Eightlaws 5. Conservation of familiarity: As an E-type system evolves all associated with it must maintain mastery of its content and behaviour to achieve satisfactory evolution. The average incremental growth remains invariant as the system evolves 54/76 incremental growth remains invariant as the system evolves 6. Continuing growth: The functional content of E-type systems must be continually increased to maintain user satisfaction over their lifetime 7. Declining quality: The quality of E-type systems will appear to be declining unless they are rigorously maintained and adapted to operational environment changes 8. Feedback system: E-type evolution processes constitute multi-level, multi-loop, multi-agent feedback systems and must be treated as such to achieve significant improvement over any reasonable base
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  Frederick Brooks Frederick Brooks –Born April 19th, 1931 – Father of Brooks’ Law Frederick Brooks *1931 55/76 – IEEE J. von Neumann Medal in 1993 – ACM Turing Award in 1999 – Cf. http://en.wikipedia.org/wiki/Fred_Brooks
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  Frederick Brooks Principle ofBrooks’ Law – Context • 1956–1964 – Manager of the IBM OS/360 development project 56/76 – Manager of the IBM OS/360 development project – Delays in the delivery – Book • The Mythical Man-Month: Essays on Software Engineering – Principle • Adding manpower to a late software project makes it later
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  Frederick Brooks – Rationale •It takes some time for the people added to a project to become productive. Brooks calls this the "ramp up" time. New workers must first become 57/76 "ramp up" time. New workers must first become educated about the work that has preceded them; also integrate with a team composed of multiple engineers who must educate the new worker in their area of expertise in the code base, day by day • Communication overheads increase as the number of people increases. The number of different communication channels increases along with the square of the number of people
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  Frederick Brooks – Comments,solutions • Brooks' Law applies to projects that are already late • The quantity, quality and role of the people added to the project also must be taken into consideration 58/76 the project also must be taken into consideration • Good management and development practices also help to minimize the impact of Brooks' Law • Rather than depending on heroes to carry the day with extraordinary efforts, Wiegers argues that a team of ordinarily-skilled individuals can repeatedly deliver timely results in the right work environment
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  Frederick Brooks – Critics “Howto quadruple your productivity with an army of student interns” 59/76 • Tolerate a little crowding • Locate next to a deep pool of hackers • Know who the best people are and only hire them • Pay well • Divide tasks to be as loosely-coupled as possible • Design your intern projects in advance
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  Edward Yourdon Edward Yourdon –Born April 20th, 1944 – “Inventor” of seven types of cohesion Edward Yourdon *1944 60/76 – Cf. http://en.wikipedia.org/wiki/Edward_Yourdon
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  Edward Yourdon Modular design –Context • 1972 – Procedural and object 61/76 – Procedural and object programming languages – Flow diagrams – Decomposition of programs in modules, classes… • 1987 – Object-oriented programming is increasingly popular
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  Edward Yourdon – Cohesioncriteria 1. Accidental: the weakest cohesion in which their is no links between methods or their link is based on a useless criteria 62/76 useless criteria – Utility classes 2. Logic: when methods are linked logically by one or more common criteria – All classes pertaining to I/O, to user interactions... 3. Temporal: when methods must be called within a common time-frame – A method and the method called in on of its catch statement, and so on
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  Edward Yourdon – Cohesioncriteria 4. Procedural: when methods must be called in a specific order – One method that check user rights and one method that 63/76 – One method that check user rights and one method that opens a file subsequently 5. Communicational: when methods process the dame set of data – All classes pertaining to dates...
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  Edward Yourdon – Cohesioncriteria 6. Sequential: when methods that process the same set of data must be called in a specific order – A parser: inputs to one class are the outputs of another 64/76 – A parser: inputs to one class are the outputs of another 7. Functional: highest level of cohesion, when a class or module is dedicated to a unique task – Classes that contribute in implementing some requirements
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  Barbara Liskov Barbara Liskov –Born November 7th, 1939 – Mother of the Liskov’s substitution principle Barbara Liskov *1939 65/76 – IEEE J. von Neumann Medal in 2004 – ACM Turing Award in 2008 – Cf. http://en.wikipedia.org/wiki/ Liskov_substitution_principle
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  Barbara Liskov Liskov’s substitutionprinciple – Context • 1987 – Object-oriented programming is increasingly popular 66/76 – Object-oriented programming is increasingly popular – Principle • Let q(x) be a property provable about objects x of type T. Then q(y) should be true for objects y of type S where S is a subtype of T
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  Barbara Liskov – Principle •Behavioural sub-typing is different and stronger than the concept of sub-typing in type theory • In type theory 67/76 • In type theory – Contravariance of parameters: a parameter of type T can accept object of type S, where S is a sub-type of T – Covariance of return type: the return type can be “enlarged” from T to S • In addition – Pre-conditions cannot be stronger in a sub-type – Post-conditions cannot be weaker in a sub-type – The sub-type S must preserve the invariants of type T
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  Barbara Liskov – Implementationin Java • Java < 1.5 – Redefinition /* Mother class */ public T foo(String a, String b) {...} 68/76 /* Daughter class */ public T foo(String a, String b) {...} – Overriding /* Mother class */ public T foo(String a, String b) {...} /* Daughter class */ public T foo(String a, Integer c) {...} • Java > 1.5 – Redefinition /* Mother class */ public T foo(String a, String b) {...} /* Daughter class */ public S foo(String a, String b) {...}
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  Erich Gamma Erich Gamma –Born in 1961 – Father of the software design patterns Erich Gamma *1961 69/76 Dahl-Nygaard Prizes in 2006 – Cf. http://en.wikipedia.org/wiki/Erich_Gamma – Cf. http://c2.com/cgi/wiki?ErichGamma
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  Erich Gamma Software designpatterns – Context • 1977 et 1979 – Christopher Alexander 70/76 – Christopher Alexander – A Pattern Language: Towns, Buildings, Construction and the idea of generative patterns – The Timeless Way of Building and the idea of perfection in architecture • 1990 – Object-oriented programs are becoming mainstream
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  Erich Gamma A PatternLanguage: Towns, Buildings, Construction – 253 patterns – Generative grammar – “At the core... is the idea that people should design for themselves their own houses, streets and communities. 71/76 themselves their own houses, streets and communities. This idea... comes simply from the observation that most of the wonderful places of the world were not made by architects but by the people” Design Patterns: Elements of Reusable Object- Oriented Software – 23 patterns – Not a language? – “Dynamic, highly parameterized software is harder to understand and build than more static software”
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  Erich Gamma Design Patterns: Elementsof Reusable Object-Oriented Software 72/76 Software – Dahl-Nygaard Prizes à • Ralph Johnson • Richard Helm • Erich Gamma • † John Vlissides
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  Grady Booch Grady Booch –Born February 27th, 1955 – Father of the UML with Jacobson et Rumbaugh Grady Booch *1955 73/76 Stevens Award in 2003 – Cf. http://en.wikipedia.org/wiki/Grady_Booch
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  Grady Booch UML – Context 74/76
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  Grady Booch – ThreeAmigos and their methods • Grady Booch, – Booch Method (design) • Ivar Jacobson 75/76 • Ivar Jacobson – Object Oriented Software Engineering, OOSE (use cases) • James Rumbaugh – Object Modeling Technique, OMT (analysis) • Rational Software Corporation – UML
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  To Be Continued ACMA. M. Turing Award – Cf. http://awards.acm.org/homepage.cfm? awd=140 AITO Dahl-Nygaard Prize 76/76 AITO Dahl-Nygaard Prize – http://www.aito.org/Dahl-Nygaard/ IEEE J. von Neumann Medal – Cf. http://www.ieee.org/about/awards/bios/ vonneumann_recipients.html