La salvaguardia degli interessi consolidati, dei clan e dei privilegi è in conflitto con la valorizzazione del merito e della competenza individuali.
Accade in tutto il mondo. Nei paesi vitali, la valorizzazione del merito e delle competenze (nella scuola e nel mondo del lavoro) trainano l'economia e la società. In Italia, come nel terzo mondo, di solito la difesa dei privilegi e l'appartenenza a un clan hanno la meglio.
La percezione diffusa in Italia è che studiare sia inutile, e che lavorare con coscienza, professionalità e impegno non produca alcun beneficio per chi lo fa. Ecco perché l'Italia scivola nel terzo mondo.
23 dicembre 2007
Il pianeta dove scomparivano le cose
Roberto Casati e Achille Varzi: Il pianeta dove scomparivano le cose. Esercizi di immaginazione filosofica. Einaudi 2006 .
Per bambini, e non solo. Stimolante nei temi, semplice e colloquiale nei toni, accompagnato da disegnini elementari e simpatici. Da non perdere.
Anche: Roberto Casati e Achille Varzi: Semplicità insormontabili. 39 storie filosofiche. Laterza 2004
Per bambini, e non solo. Stimolante nei temi, semplice e colloquiale nei toni, accompagnato da disegnini elementari e simpatici. Da non perdere.
Anche: Roberto Casati e Achille Varzi: Semplicità insormontabili. 39 storie filosofiche. Laterza 2004
27 novembre 2007
Testi di storia dell'informatica
Su Mondo Digitale settembre 2007 (rivista dell'AICA) c'è un articolo di Corrado Bonfanti "Corsi di Storia dell'Informatica nelle università italiane".
Cita i testi di storia dell'informatica più utilizzati dai docenti:
Letture consigliate: le più gettonate
Opere che i docenti hanno suggerito a chi volesse approfondire.
Il numero di ❑ indica il rispettivo score.
❑ ❑ ❑ ❑ M.R. Williams: A History of Computing Technology. Prentice-Hall, 1985.
Trad.it. [possibilmente da evitare!] Storia dei computer. Dall’abaco ai calcolatori elettronici. Franco Muzzio, 1989.
❑ ❑ W. Aspray (editor): Computing Before Computers. Iowa State University Press, 1990.
❑ ❑ P.E. Ceruzzi: A History of Modern Computing. The MIT Press, 2003 (2nd ed.).
Trad.it. Storia dell’informatica: dai primi computer digitali all’era di internet. Apogeo, 2006.
❑ ❑ M. Davis: The Universal Computer – The road from Leibniz to Turing; 2000.
Trad.it. Il calcolatore universale: da Leibniz a Turing. Adelphi, 2004.
❑ M. Calvo, F. Ciotti, G. Roncaglia, M.A. Zela: Internet 2004. Laterza, 2003.
❑ M. Campbell-Kelly, W. Aspray: Computer: A History of the Information Machine. Basic Books - HarperCollins Publishers, 1996.
❑ A.D. Chandler: Inventing the Electronic Century. The Free Press, 2001.
Trad.it. La rivoluzione elettronica. Egea - Università Bocconi editore, 2003.
❑ G. Ifrah: Histoire universelle des Chiffres. Éditions Seghers, 1981.
Trad.it. Storia universale dei numeri. Arnoldo Mondadori, 1983.
❑ M. Morelli: Dalle calcolatrici ai computer degli anni cinquanta. Franco Angeli, 2001.
❑ R.W. Sebesta: Concepts of Programming Languages. Addison-Wesley, 2006 (7th ed.).
Cita i testi di storia dell'informatica più utilizzati dai docenti:
Letture consigliate: le più gettonate
Opere che i docenti hanno suggerito a chi volesse approfondire.
Il numero di ❑ indica il rispettivo score.
❑ ❑ ❑ ❑ M.R. Williams: A History of Computing Technology. Prentice-Hall, 1985.
Trad.it. [possibilmente da evitare!] Storia dei computer. Dall’abaco ai calcolatori elettronici. Franco Muzzio, 1989.
❑ ❑ W. Aspray (editor): Computing Before Computers. Iowa State University Press, 1990.
❑ ❑ P.E. Ceruzzi: A History of Modern Computing. The MIT Press, 2003 (2nd ed.).
Trad.it. Storia dell’informatica: dai primi computer digitali all’era di internet. Apogeo, 2006.
❑ ❑ M. Davis: The Universal Computer – The road from Leibniz to Turing; 2000.
Trad.it. Il calcolatore universale: da Leibniz a Turing. Adelphi, 2004.
❑ M. Calvo, F. Ciotti, G. Roncaglia, M.A. Zela: Internet 2004. Laterza, 2003.
❑ M. Campbell-Kelly, W. Aspray: Computer: A History of the Information Machine. Basic Books - HarperCollins Publishers, 1996.
❑ A.D. Chandler: Inventing the Electronic Century. The Free Press, 2001.
Trad.it. La rivoluzione elettronica. Egea - Università Bocconi editore, 2003.
❑ G. Ifrah: Histoire universelle des Chiffres. Éditions Seghers, 1981.
Trad.it. Storia universale dei numeri. Arnoldo Mondadori, 1983.
❑ M. Morelli: Dalle calcolatrici ai computer degli anni cinquanta. Franco Angeli, 2001.
❑ R.W. Sebesta: Concepts of Programming Languages. Addison-Wesley, 2006 (7th ed.).
10 novembre 2007
Refactoring
da IEEE Software, Sep/Oct 2007, J.B.Rainsberger a pag. 27:
"You already need to refactor your system, but there's never a good time to start refactoring, so start now."
"You already need to refactor your system, but there's never a good time to start refactoring, so start now."
Avvocati
da Hernando De Soto - The Mistery of Capital. Why Capitalism Triumphs in the West and Fails Everywhere Else - Basic Books 2000, p. 199
"Using economic data from fifty-two countries from 1960 to 1980, Samar K. Datta and Jefferey B. Nugent have shown that for every percentage point increase in the number of lawyers in the labor force (from, say, 0.5 to 1.5 percent), economic growth is reduced by 4.76 to 3.68 percent - thus showing that economic growth is inversely related to the prudence of lawyers."
"Using economic data from fifty-two countries from 1960 to 1980, Samar K. Datta and Jefferey B. Nugent have shown that for every percentage point increase in the number of lawyers in the labor force (from, say, 0.5 to 1.5 percent), economic growth is reduced by 4.76 to 3.68 percent - thus showing that economic growth is inversely related to the prudence of lawyers."
07 novembre 2007
Due punti come separatore
Ancora Alessandro Manzoni citato nel libro di Gensini, questa volta da un testo del 1868, "Dell'unità della lingua e dei mezzi di diffonderla".
"Ci pare di dover distinguere i mezzi che sarebbe fattibile di mettere in pratica, anche senza attendere la formazione del nuovo vocabolario, da quegli altri che, di necessità, devono seguirne la pubblicazione.
I primi sarebbero: insegnanti di Toscana, nel maggior numero possibile, o anche educati in Toscana, da mandarsi nelle scuole primarie delle diverse province; esclusivamente toscani, ove ce ne sia, per le cattedre di lingua nelle scuole magistrali e normali:
Alcuni sussidi, sui fondi appositi iscritti per le scuole primarie nel bilancio del Ministero dell'istruzione pubblica, da assegnarsi a que' Comuni che si provvedessero di maestri nati od educati in Toscana:
Conferenze tra l'anno, od anche solo ne' mesi autunnali, nelle quali de' maestri e delle maestre di Toscana si rechino nelle varie province, per intrattenere i maestri e le maestre delle scuole primarie in letture di libri classici e di libri moderni (pezzi opportunamente scelti) notando gli arcaismi dei primi, e sostituendo le locuzioni dell'uso, avvertendo i provincialismi, i neologismi inutili de' secondi, colla stessa sostituzione:
Persone competenti, delegate nelle città capoluoghi dalla primaria magistratura, ed ufizialmente, che rivedano non solo qualunque iscrizione, avviso, od insegna devasi esporre in pubblico, ma anche le notizie che gli uffici regi o municipali forniscono ai giornalisti, per le loro cronache quotidiane:
Abbecedari, catechismi e primi libri di lettura nelle scuole, scritti o almeno riveduti da Toscani, sempre colla mira di cercare la diffusione della lingua viva:
Dare, come premio, a qualche allievo ed allieva delle scuole normali e magistrali, che ne abbiano fornito il corso con profitto e segni d'eminente capacità, il mezzo di passare un'annata scolastica in Firenze, per farci la pratica in una delle migliori scuole primarie:
Raccomandare ai membri de' corpi scientifici, quando la trattazione delle materie essenziali ne concedesse loro il tempo, di determinare fra loro le norme per una concorde e costante nomenclatura in que' rami scientifici che sono più accessibili al pubblico, come la storia naturale, la meccanica, la matallurgia, ecc.
I mezzi di diffusione poi, i quali dovrebbero seguire la pubblicazione del nuovo vocabolario sarebbero:
Provvedere che tutte le scuole governative, cos' dette secondarie, abbiano per ciascuna classe, degli esemplari del nuovo vocabolario, in quantità proporzionata al numero degli alunni:
Curare che del vocabolario si faccia anche un'edizione la più economica possibile, per renderne facile l'acquisto a ciascuno scolare:
Avere, per le scuole elementari ed anche per le scuole tecniche, de' piccoli vocabolari domestici d'arti e mestieri, compilati sul nuovo vocabolario della lingua, e alcuni, anche, figurati:
Dare in premio, nelle diverse scuole, insieme ad un'opera di bona letteratura, una copia del vocabolario, od anche, secondo la scuola, de' piccoli vocabolari che ne sono estratti:
Cercare che, anche in tutte le scuole femminili, i libri i più elementari sieno raccomandati o prescritti in modo che si diffonda sempre più, nelle città e nelle campagne, la cognizione della bona lingua viva, affinché si giunga così, a poco a poco, a renderla nota e familiare anche ai bambini."
"Ci pare di dover distinguere i mezzi che sarebbe fattibile di mettere in pratica, anche senza attendere la formazione del nuovo vocabolario, da quegli altri che, di necessità, devono seguirne la pubblicazione.
I primi sarebbero: insegnanti di Toscana, nel maggior numero possibile, o anche educati in Toscana, da mandarsi nelle scuole primarie delle diverse province; esclusivamente toscani, ove ce ne sia, per le cattedre di lingua nelle scuole magistrali e normali:
Alcuni sussidi, sui fondi appositi iscritti per le scuole primarie nel bilancio del Ministero dell'istruzione pubblica, da assegnarsi a que' Comuni che si provvedessero di maestri nati od educati in Toscana:
Conferenze tra l'anno, od anche solo ne' mesi autunnali, nelle quali de' maestri e delle maestre di Toscana si rechino nelle varie province, per intrattenere i maestri e le maestre delle scuole primarie in letture di libri classici e di libri moderni (pezzi opportunamente scelti) notando gli arcaismi dei primi, e sostituendo le locuzioni dell'uso, avvertendo i provincialismi, i neologismi inutili de' secondi, colla stessa sostituzione:
Persone competenti, delegate nelle città capoluoghi dalla primaria magistratura, ed ufizialmente, che rivedano non solo qualunque iscrizione, avviso, od insegna devasi esporre in pubblico, ma anche le notizie che gli uffici regi o municipali forniscono ai giornalisti, per le loro cronache quotidiane:
Abbecedari, catechismi e primi libri di lettura nelle scuole, scritti o almeno riveduti da Toscani, sempre colla mira di cercare la diffusione della lingua viva:
Dare, come premio, a qualche allievo ed allieva delle scuole normali e magistrali, che ne abbiano fornito il corso con profitto e segni d'eminente capacità, il mezzo di passare un'annata scolastica in Firenze, per farci la pratica in una delle migliori scuole primarie:
Raccomandare ai membri de' corpi scientifici, quando la trattazione delle materie essenziali ne concedesse loro il tempo, di determinare fra loro le norme per una concorde e costante nomenclatura in que' rami scientifici che sono più accessibili al pubblico, come la storia naturale, la meccanica, la matallurgia, ecc.
I mezzi di diffusione poi, i quali dovrebbero seguire la pubblicazione del nuovo vocabolario sarebbero:
Provvedere che tutte le scuole governative, cos' dette secondarie, abbiano per ciascuna classe, degli esemplari del nuovo vocabolario, in quantità proporzionata al numero degli alunni:
Curare che del vocabolario si faccia anche un'edizione la più economica possibile, per renderne facile l'acquisto a ciascuno scolare:
Avere, per le scuole elementari ed anche per le scuole tecniche, de' piccoli vocabolari domestici d'arti e mestieri, compilati sul nuovo vocabolario della lingua, e alcuni, anche, figurati:
Dare in premio, nelle diverse scuole, insieme ad un'opera di bona letteratura, una copia del vocabolario, od anche, secondo la scuola, de' piccoli vocabolari che ne sono estratti:
Cercare che, anche in tutte le scuole femminili, i libri i più elementari sieno raccomandati o prescritti in modo che si diffonda sempre più, nelle città e nelle campagne, la cognizione della bona lingua viva, affinché si giunga così, a poco a poco, a renderla nota e familiare anche ai bambini."
Alessandro Manzoni e l'ingegno
"I doni dell'ingegno non si acquistano, come lo indica il nome stesso; ma tutto ciò che lo studio, che la diligenza possono dare, non istarebbe certamente per me ch'io non lo acquistassi."
è dalla seconda Introduzione (1823) a "Fermo e Lucia".
Riportato da Stefano Gensini, "Breve storia dell'educazione linguistica dall'Unità ad oggi", Carocci 2005. Tra l'altro, il libro tratta il difficile e tormentato processo che ha portato all'adozione generalizzata di una lingua italiana unitaria a partire dai dialetti. Molte affinità con il processo che stiamo vivendo in direzione di un'adozione generalizzata della lingua inglese.
è dalla seconda Introduzione (1823) a "Fermo e Lucia".
Riportato da Stefano Gensini, "Breve storia dell'educazione linguistica dall'Unità ad oggi", Carocci 2005. Tra l'altro, il libro tratta il difficile e tormentato processo che ha portato all'adozione generalizzata di una lingua italiana unitaria a partire dai dialetti. Molte affinità con il processo che stiamo vivendo in direzione di un'adozione generalizzata della lingua inglese.
Education: how to be top
Economist, October 20th 2007, p.74-75
"What works in education: the lessons according to McKinsey
There are big variations in educational standards between countries. These have been measured and re-measured by the OECD's Programme for International Student Assessment (PISA) which has established, first, that the best performing countries do much better than the worst and, second, that the same countries head such league tables again and again: Canada, Finland, Japan, Singapore, South Korea.
Those findings raise what ought to be a fruitful question: what do the successful lot have in common? Yet the answer to that has proved surprisingly elusive. Not more money. Singapore spends less per student than most. Nor more study time. Finnish students begin school later, and study fewer hours, than in other rich countries.
Now, an organisation from outside the teaching fold—McKinsey, a consultancy that advises companies and governments—has boldly gone where educationalists have mostly never gone: into policy recommendations based on the PISA findings. Schools, it says*, need to do three things: get the best teachers; get the best out of teachers; and step in when pupils start to lag behind. That may not sound exactly “first-of-its-kind” (which is how Andreas Schleicher, the OECD's head of education research, describes McKinsey's approach): schools surely do all this already? Actually, they don't. If these ideas were really taken seriously, they would change education radically.
Begin with hiring the best. There is no question that, as one South Korean official put it, “the quality of an education system cannot exceed the quality of its teachers.” Studies in Tennessee and Dallas have shown that, if you take pupils of average ability and give them to teachers deemed in the top fifth of the profession, they end up in the top 10% of student performers; if you give them to teachers from the bottom fifth, they end up at the bottom. The quality of teachers affects student performance more than anything else.
[...] Teaching the teachers
Having got good people, there is a temptation to shove them into classrooms and let them get on with it. For understandable reasons, teachers rarely get much training in their own classrooms (in contrast, doctors do a lot of training in hospital wards). But successful countries can still do much to overcome the difficulty.
Singapore provides teachers with 100 hours of training a year and appoints senior teachers to oversee professional development in each school. In Japan and Finland, groups of teachers visit each others' classrooms and plan lessons together. In Finland, they get an afternoon off a week for this. In Boston, which has one of America's most improved public-school systems, schedules are arranged so that those who teach the same subject have free classes together for common planning. This helps spread good ideas around. As one educator remarked, “when a brilliant American teacher retires, almost all of the lesson plans and practices that she has developed also retire. When a Japanese teacher retires, she leaves a legacy.”
[...] But there is a pattern in what countries do once pupils and schools start to fail. The top performers intervene early and often. Finland has more special-education teachers devoted to laggards than anyone else—as many as one teacher in seven in some schools. In any given year, a third of pupils get one-on-one remedial lessons. Singapore provides extra classes for the bottom 20% of students and teachers are expected to stay behind—often for hours—after school to help students.
None of this is rocket science. Yet it goes against some of the unspoken assumptions of education policy. Scratch a teacher or an administrator (or a parent), and you often hear that it is impossible to get the best teachers without paying big salaries; that teachers in, say, Singapore have high status because of Confucian values; or that Asian pupils are well behaved and attentive for cultural reasons. McKinsey's conclusions seem more optimistic: getting good teachers depends on how you select and train them; teaching can become a career choice for top graduates without paying a fortune; and that, with the right policies, schools and pupils are not doomed to lag behind.
"What works in education: the lessons according to McKinsey
There are big variations in educational standards between countries. These have been measured and re-measured by the OECD's Programme for International Student Assessment (PISA) which has established, first, that the best performing countries do much better than the worst and, second, that the same countries head such league tables again and again: Canada, Finland, Japan, Singapore, South Korea.
Those findings raise what ought to be a fruitful question: what do the successful lot have in common? Yet the answer to that has proved surprisingly elusive. Not more money. Singapore spends less per student than most. Nor more study time. Finnish students begin school later, and study fewer hours, than in other rich countries.
Now, an organisation from outside the teaching fold—McKinsey, a consultancy that advises companies and governments—has boldly gone where educationalists have mostly never gone: into policy recommendations based on the PISA findings. Schools, it says*, need to do three things: get the best teachers; get the best out of teachers; and step in when pupils start to lag behind. That may not sound exactly “first-of-its-kind” (which is how Andreas Schleicher, the OECD's head of education research, describes McKinsey's approach): schools surely do all this already? Actually, they don't. If these ideas were really taken seriously, they would change education radically.
Begin with hiring the best. There is no question that, as one South Korean official put it, “the quality of an education system cannot exceed the quality of its teachers.” Studies in Tennessee and Dallas have shown that, if you take pupils of average ability and give them to teachers deemed in the top fifth of the profession, they end up in the top 10% of student performers; if you give them to teachers from the bottom fifth, they end up at the bottom. The quality of teachers affects student performance more than anything else.
[...] Teaching the teachers
Having got good people, there is a temptation to shove them into classrooms and let them get on with it. For understandable reasons, teachers rarely get much training in their own classrooms (in contrast, doctors do a lot of training in hospital wards). But successful countries can still do much to overcome the difficulty.
Singapore provides teachers with 100 hours of training a year and appoints senior teachers to oversee professional development in each school. In Japan and Finland, groups of teachers visit each others' classrooms and plan lessons together. In Finland, they get an afternoon off a week for this. In Boston, which has one of America's most improved public-school systems, schedules are arranged so that those who teach the same subject have free classes together for common planning. This helps spread good ideas around. As one educator remarked, “when a brilliant American teacher retires, almost all of the lesson plans and practices that she has developed also retire. When a Japanese teacher retires, she leaves a legacy.”
[...] But there is a pattern in what countries do once pupils and schools start to fail. The top performers intervene early and often. Finland has more special-education teachers devoted to laggards than anyone else—as many as one teacher in seven in some schools. In any given year, a third of pupils get one-on-one remedial lessons. Singapore provides extra classes for the bottom 20% of students and teachers are expected to stay behind—often for hours—after school to help students.
None of this is rocket science. Yet it goes against some of the unspoken assumptions of education policy. Scratch a teacher or an administrator (or a parent), and you often hear that it is impossible to get the best teachers without paying big salaries; that teachers in, say, Singapore have high status because of Confucian values; or that Asian pupils are well behaved and attentive for cultural reasons. McKinsey's conclusions seem more optimistic: getting good teachers depends on how you select and train them; teaching can become a career choice for top graduates without paying a fortune; and that, with the right policies, schools and pupils are not doomed to lag behind.
28 settembre 2007
18 settembre 2007
Tyler Cowen - How to work and play a little better
The Economist, September 8th 2007
Mr Cowen is a professor of economics at George Mason University in Fairfax, Virgina, and a co-owner of marginalrevolution.com, one of the best economics blogs on the internet.
“Discover Your Inner Economist” joins a recent school of books demystifying and popularising economics that began with Steven Landsburg's “Armchair Economist” in 1993, and conquered the bestseller lists in 2005 with “Freakonomics” by Steven Levitt and Stephen Dubner. It stands apart from its predecessors by making its revelations not so much about the way the world works as about the way we ourselves work (and play) and how we can take practical steps to do both better.
Tyler Cowen: Discover Your Inner Economist: Use Incentives to Fall in Love, Survive Your Next Meeting, and Motivate Your Dentist - Dutton 2007
Mr Cowen is a professor of economics at George Mason University in Fairfax, Virgina, and a co-owner of marginalrevolution.com, one of the best economics blogs on the internet.
“Discover Your Inner Economist” joins a recent school of books demystifying and popularising economics that began with Steven Landsburg's “Armchair Economist” in 1993, and conquered the bestseller lists in 2005 with “Freakonomics” by Steven Levitt and Stephen Dubner. It stands apart from its predecessors by making its revelations not so much about the way the world works as about the way we ourselves work (and play) and how we can take practical steps to do both better.
Tyler Cowen: Discover Your Inner Economist: Use Incentives to Fall in Love, Survive Your Next Meeting, and Motivate Your Dentist - Dutton 2007
Lustiger, cardinale cattolico, ed ebreo
From The Economist, Aug 16th 2007
Aaron Jean-Marie Lustiger, cardinale di Parigi, ebreo di origini polacche; sua madre morì ad Auschwitz.
AT THE funeral of Jean-Marie Lustiger, at Notre Dame de Paris on August 10th, his second cousin Jonas Moses-Lustiger read a psalm in Hebrew and placed on the coffin a jar of earth that had been gathered on the Mount of Olives. Then another cousin, Arno Lustiger, bent over the coffin to recite Kaddish. Only when those things were done was the body of Cardinal Lustiger carried inside the cathedral, where Catholic panoply took over.
There was no question of mixing the rites; the cardinal, said his staff, would not have liked that. Yet they were mixed in himself. He was a Jew by birth, instinct, emotion and devotion; he was a Catholic by conversion and conviction. He cracked Jewish jokes, and put on a suit and kippa to go to synagogue, although the evening would find him in his soutane again. For him, Christianity was simply the fruit of Judaism; his first religion came to completion in his second. Christ, in his eyes, was the Messiah of Israel, his cross worthy of a yellow star. And since the mission of Israel was “to bring light to the goyim”, preaching the gospel became his own mitzvah.
Every detail of his funeral, with its two rites, he carefully arranged himself. Then he wrote his epitaph:
I was born Jewish. I received the name of my paternal grandfather, Aaron. Having become Christian by faith and baptism, I have remained Jewish. As did the Apostles.
Aaron Jean-Marie Lustiger, cardinale di Parigi, ebreo di origini polacche; sua madre morì ad Auschwitz.
AT THE funeral of Jean-Marie Lustiger, at Notre Dame de Paris on August 10th, his second cousin Jonas Moses-Lustiger read a psalm in Hebrew and placed on the coffin a jar of earth that had been gathered on the Mount of Olives. Then another cousin, Arno Lustiger, bent over the coffin to recite Kaddish. Only when those things were done was the body of Cardinal Lustiger carried inside the cathedral, where Catholic panoply took over.
There was no question of mixing the rites; the cardinal, said his staff, would not have liked that. Yet they were mixed in himself. He was a Jew by birth, instinct, emotion and devotion; he was a Catholic by conversion and conviction. He cracked Jewish jokes, and put on a suit and kippa to go to synagogue, although the evening would find him in his soutane again. For him, Christianity was simply the fruit of Judaism; his first religion came to completion in his second. Christ, in his eyes, was the Messiah of Israel, his cross worthy of a yellow star. And since the mission of Israel was “to bring light to the goyim”, preaching the gospel became his own mitzvah.
Every detail of his funeral, with its two rites, he carefully arranged himself. Then he wrote his epitaph:
I was born Jewish. I received the name of my paternal grandfather, Aaron. Having become Christian by faith and baptism, I have remained Jewish. As did the Apostles.
11 settembre 2007
The Chimera of Software Quality
by Les Hatton, in IEEE Computer, August 2007.
"Nobody knows how to produce a fault-free program. Nobody even knows how to prove it even supposing one we were magically provided. I teach my students that in their whole careers, they are unlikely ever to produce a fault-free program and if they did, they would never know it, they could never prove it and they could not systematically repeat it. It provides a usefully humble starting point.
[...] I've analysed enough failed systems in my time to know that there are two classic symptoms of a system on its way to the fairies. First, no independent audit is allowed and second, talking heads tell you everything is fine when the ultimate users tell you the opposite.
[...] The Linux kernel is now arguably the most reliable complex software application
humanity race has yet produced, with a mean time between failures reported in tens and in some cases, hundreds of years. Poetically, the development environment of Linux, which leverages the contributions of thousands of Web volunteers who give their spare time for the public good, breaks just about every rule which software process experts hold dear."
"Nobody knows how to produce a fault-free program. Nobody even knows how to prove it even supposing one we were magically provided. I teach my students that in their whole careers, they are unlikely ever to produce a fault-free program and if they did, they would never know it, they could never prove it and they could not systematically repeat it. It provides a usefully humble starting point.
[...] I've analysed enough failed systems in my time to know that there are two classic symptoms of a system on its way to the fairies. First, no independent audit is allowed and second, talking heads tell you everything is fine when the ultimate users tell you the opposite.
[...] The Linux kernel is now arguably the most reliable complex software application
humanity race has yet produced, with a mean time between failures reported in tens and in some cases, hundreds of years. Poetically, the development environment of Linux, which leverages the contributions of thousands of Web volunteers who give their spare time for the public good, breaks just about every rule which software process experts hold dear."
20 agosto 2007
Parnas on abstractions
Communications of the ACM, June 2007, p.7
"Use the Simplest Model, But Not Too Simple
Jeff Kramer's view, expressed in his article "Is Abstraction the Key to Computing?" (Apr. 2007), that abstraction is indeed a key concept in computing, especially in software design, is correct but far from new. It's a lesson I learned from the late E.W. Dijkstra 40 years ago and underlies every software development method proposed since then. Dijkstra said many useful things. Among them is the most useful definition of "abstraction" I know: "An abstraction is one thing that represents several real things equally well." This positive definition is more useful than the more typical ones Kramer quoted that emphasize the elimination of information. Dijkstra's clarifies what must remain.
Dijkstra's definition allows us to distinguish between an abstraction and a lie. When a model makes assumptions that are not true of a real object (such as infinite memory), these assumptions are often defended by saying "It is an abstraction." Using Dijkstra's definition, such models are not abstractions. Rather than represent several things equally well, they represent nothing at all. Because they embody unrealistic assumptions, one cannot trust the conclusions that might be drawn from them.
Models that are not abstractions in Dijkstra's sense may provide insight or understanding but can also mislead. Programs based on them may not work, and theories based on them may yield results not relevant in the real world.
Many computer science courses fail to teach students how to develop abstractions because they use models that are not abstractions but lies. Students must be taught the implications of an idea often attributed to Albert Einstein: "Everything should be as simple as possible but not simpler." Finding the simplest model that is not a lie is the key to better software design."
David Lorge Parnas
Limerick, Ireland
"Use the Simplest Model, But Not Too Simple
Jeff Kramer's view, expressed in his article "Is Abstraction the Key to Computing?" (Apr. 2007), that abstraction is indeed a key concept in computing, especially in software design, is correct but far from new. It's a lesson I learned from the late E.W. Dijkstra 40 years ago and underlies every software development method proposed since then. Dijkstra said many useful things. Among them is the most useful definition of "abstraction" I know: "An abstraction is one thing that represents several real things equally well." This positive definition is more useful than the more typical ones Kramer quoted that emphasize the elimination of information. Dijkstra's clarifies what must remain.
Dijkstra's definition allows us to distinguish between an abstraction and a lie. When a model makes assumptions that are not true of a real object (such as infinite memory), these assumptions are often defended by saying "It is an abstraction." Using Dijkstra's definition, such models are not abstractions. Rather than represent several things equally well, they represent nothing at all. Because they embody unrealistic assumptions, one cannot trust the conclusions that might be drawn from them.
Models that are not abstractions in Dijkstra's sense may provide insight or understanding but can also mislead. Programs based on them may not work, and theories based on them may yield results not relevant in the real world.
Dijkstra's work showed that two distinct skills are related to abstractions:
- Being able to work with a given abstraction; and
- Being able to develop a useful abstraction.
Many computer science courses fail to teach students how to develop abstractions because they use models that are not abstractions but lies. Students must be taught the implications of an idea often attributed to Albert Einstein: "Everything should be as simple as possible but not simpler." Finding the simplest model that is not a lie is the key to better software design."
David Lorge Parnas
Limerick, Ireland
30 maggio 2007
The Sarbanes-Oxley Act: implications for large-scale IT outsourcing
James A. Hall, Stephen L. Liedtka, "The Sarbanes-Oxley Act: implications for large-scale IT outsourcing", Comm ACM 03-2007
"Until they are certain that outsourcing IT management is the best possible option, firms would do well to maintain and invest in their own in-house IT assets.
[...]
Two sections of SOX are especially important to corporate IT departments:
Section 404. Called “Management Assessment of Internal Controls,” it mandates that corporate CEOs implement internal controls over their financial reporting systems, physically test these controls, and certify in writing that they function correctly. As a practical matter, the vast majority of controls are embedded in computer technologies that involve virtually
all of an organization’s financial transaction processing systems; and
Section 302. Called “Corporate Responsibility for Incident Reports,” it requires senior financial executives to disclose deficiencies in internal controls and fraud (whether material or not). Also, public accounting firms must attest in their audit opinions to the adequacy
and function of their client firms’ internal controls. Prior to SOX, auditing standards required
auditors only to be “familiar” with internal controls.
[...]
While large-scale IT outsourcing may appear to be a way to address the costs of SOX compliance, outsourcing contracts can actually increase the likelihood that a firm will fail to
comply with both the detail and the spirit of SOX.
Specifically, large-scale IT outsourcing increases the risk that top management and boards of directors will be unable to fulfill their oversight duties; that firms will employ ineffective internal controls over financial statements; that financial reports will be inaccurate
and/or misleading; and that firms will fail to protect shareholder wealth.
[...]
Finally, we note that an outsourcing client’s competitive success depends on the vendor’s ability to perform. Electronic Data Systems Corp. (EDS) has demonstrated the potential for vendor failures to have drastic, perhaps unforeseeable, financial repercussions.
EDS has struggled due to a variety of factors, including its own financial reporting failures and the bankruptcies of two of its largest customers—WorldCom and US Airways. In order to cut costs, EDS terminated 7,000 employees, which affected its ability to serve its clients. Following an 11-year low in share prices in 2002, EDS stockholders filed a class-action
lawsuit against the company. Vendors experiencing such serious financial and legal problems clearly threaten the viability of their strategic partners, as well as their ability to maintain internal controls and completely and accurately present financial information."
"Until they are certain that outsourcing IT management is the best possible option, firms would do well to maintain and invest in their own in-house IT assets.
[...]
Two sections of SOX are especially important to corporate IT departments:
Section 404. Called “Management Assessment of Internal Controls,” it mandates that corporate CEOs implement internal controls over their financial reporting systems, physically test these controls, and certify in writing that they function correctly. As a practical matter, the vast majority of controls are embedded in computer technologies that involve virtually
all of an organization’s financial transaction processing systems; and
Section 302. Called “Corporate Responsibility for Incident Reports,” it requires senior financial executives to disclose deficiencies in internal controls and fraud (whether material or not). Also, public accounting firms must attest in their audit opinions to the adequacy
and function of their client firms’ internal controls. Prior to SOX, auditing standards required
auditors only to be “familiar” with internal controls.
[...]
While large-scale IT outsourcing may appear to be a way to address the costs of SOX compliance, outsourcing contracts can actually increase the likelihood that a firm will fail to
comply with both the detail and the spirit of SOX.
Specifically, large-scale IT outsourcing increases the risk that top management and boards of directors will be unable to fulfill their oversight duties; that firms will employ ineffective internal controls over financial statements; that financial reports will be inaccurate
and/or misleading; and that firms will fail to protect shareholder wealth.
[...]
Finally, we note that an outsourcing client’s competitive success depends on the vendor’s ability to perform. Electronic Data Systems Corp. (EDS) has demonstrated the potential for vendor failures to have drastic, perhaps unforeseeable, financial repercussions.
EDS has struggled due to a variety of factors, including its own financial reporting failures and the bankruptcies of two of its largest customers—WorldCom and US Airways. In order to cut costs, EDS terminated 7,000 employees, which affected its ability to serve its clients. Following an 11-year low in share prices in 2002, EDS stockholders filed a class-action
lawsuit against the company. Vendors experiencing such serious financial and legal problems clearly threaten the viability of their strategic partners, as well as their ability to maintain internal controls and completely and accurately present financial information."
The effects of online advertising
Scott McCoy, Andrea Everard, Peter Polak, Dennis F. Galletta: The effects of online advertising, Comm ACM 03-2007
"Our findings suggest that advertisements do have significant effects on retention of the site. Also, advertising content that is non-congruent with the site’s content seems to lead to greater effort in reconciling the differing content, and ultimately greater memory of both the Web site and the advertisement. Intrusiveness is also important for both Web site designers and advertisers. Pop-ups and pop-unders seem to be more intrusive than in-line ads, implying
that users should not be interrupted from their online tasks to close the extraneous windows.
[...]
Designers should realize the magnitude of ill effects caused by advertising.
Although some of the differences were not large in magnitude, reducing the likelihood of a person’s return by 11% might be a cost that is too great for a site host to bear. Discovering that pop-up and in-line ads differ greatly in measures of intrusiveness, a host might play it safe and make use of in-line ads. As theory and practice begin to converge in this area, perhaps
what has been described so often as a wild new frontier might finally take a few steps toward being tamed."
"Our findings suggest that advertisements do have significant effects on retention of the site. Also, advertising content that is non-congruent with the site’s content seems to lead to greater effort in reconciling the differing content, and ultimately greater memory of both the Web site and the advertisement. Intrusiveness is also important for both Web site designers and advertisers. Pop-ups and pop-unders seem to be more intrusive than in-line ads, implying
that users should not be interrupted from their online tasks to close the extraneous windows.
[...]
Designers should realize the magnitude of ill effects caused by advertising.
Although some of the differences were not large in magnitude, reducing the likelihood of a person’s return by 11% might be a cost that is too great for a site host to bear. Discovering that pop-up and in-line ads differ greatly in measures of intrusiveness, a host might play it safe and make use of in-line ads. As theory and practice begin to converge in this area, perhaps
what has been described so often as a wild new frontier might finally take a few steps toward being tamed."
Theoretical Reflections on Agile Development Methodologies
Sridhar Nerur e VenuGopal Balijepally, "Theoretical Reflections on Agile Development Methodologies", Comm ACM 03-2007 . Con una lista di riferimenti eccellente.
"The progression of thought in software development parallels the maturation of design ideas in architecture and strategic management. The traditional mechanistic worldview is today being challenged by a newer agile perspective that accords primacy to uniqueness, ambiguity,
complexity, and change, as opposed to prediction, verifiability, and control. The goal of optimization is being replaced by flexibility and responsiveness.
[...]
The tenets of agile methods depart from the traditional orthodoxy of software development. This shift in philosophy is not unusual, as similar patterns of intellectual evolution have emerged in other disciplines. A look at architecture and strategic management reveals that
the progression of ideas in them is remarkably similar to conceptual pattern shifts in software design."
"The progression of thought in software development parallels the maturation of design ideas in architecture and strategic management. The traditional mechanistic worldview is today being challenged by a newer agile perspective that accords primacy to uniqueness, ambiguity,
complexity, and change, as opposed to prediction, verifiability, and control. The goal of optimization is being replaced by flexibility and responsiveness.
[...]
The tenets of agile methods depart from the traditional orthodoxy of software development. This shift in philosophy is not unusual, as similar patterns of intellectual evolution have emerged in other disciplines. A look at architecture and strategic management reveals that
the progression of ideas in them is remarkably similar to conceptual pattern shifts in software design."
21 aprile 2007
Management Theory - Rhythm and blues
Economist, March 31st 2007
"Employees may be reluctant to admit this, but managers should take heed: teams that like each other also seem to work better together".
(a partire da una riflessione sulla composizione dei ggruppi di voga nelle regate annuali che contrappongono Oxford a Cambridge).
"Employees may be reluctant to admit this, but managers should take heed: teams that like each other also seem to work better together".
(a partire da una riflessione sulla composizione dei ggruppi di voga nelle regate annuali che contrappongono Oxford a Cambridge).
25 febbraio 2007
Web Services
José Luiz Fiadeiro – Designing for Software’s Social Complexity – IEEE Computer January 2007
Gerarchie, reti, decisioni
Peter Denning e Rick Hayes-Roth - Decision Making in very Large Networks - Comm ACM November 2006.
La creazione di reti operative in situazioni di crisi (es. tsunami in est asiatico, uragano Katrina a New Orleans) richiede un coordinamento decisionale rapido ed efficiente. Questa esigenza si scontra con il fatto che i partecipanti appartengono ad organizzazioni gerarchiche
La creazione di reti operative in situazioni di crisi (es. tsunami in est asiatico, uragano Katrina a New Orleans) richiede un coordinamento decisionale rapido ed efficiente. Questa esigenza si scontra con il fatto che i partecipanti appartengono ad organizzazioni gerarchiche
Articoli su outsourcing
Hazel Taylor – Critical Risks in Outsourced IT Projects: the Intractable and the Unforeseen – Comm ACM November 2006
Phillip G. Armour – Agile... and Offshore - Comm ACM January 2007
Phillip G. Armour – Agile... and Offshore - Comm ACM January 2007
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