Grazie a Brian Marick, ho scoperto questa chicca:
Structured Procrastination, di John Perry
venerdì 28 settembre 2007
lunedì 17 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.
martedì 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."
lunedì 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
mercoledì 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."
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