March 04, 2004
Ontology Review 2: The International System of Units (SI). US Resistance to Adoption of the Metric System
The International System of Units (SI) [72 page pdf Brochure] is maintained by the Bureau International des Poids et Measures at it's headquarters in Sevres near Paris, France. The Metric System as it is often known has a long history; supposedly invented in 1670 by Gabriel Mouton, a French clergyman, It was adopted by France in 1795 and by the United States in 1866. The system gained international status with the signing of The Convention of the Meter in Paris on 20th May 1875. The U.S. was one of the original seventeen signatory nations and is the only industrialized nation that still does not use the system.
Note: At this time, only three countries - Burma, Liberia, and the US - have not adopted the International System of Units (SI, or metric system) as their official system of weights and measures. Although use of the metric system has been sanctioned by law in the US since 1866, it has been slow in displacing the American adaptation of the British Imperial System known as the U.S. Customary System. The US is the only industrialized nation that does not mainly use the metric system in its commercial and standards activities, but there is increasing acceptance in science, medicine, government, and many sectors of industry.
CIA World Fact Book. 2000
In 1971 the U.S. Metric Study by the National Bureau of Standards resulted in a Report to the Congress called "A Metric America, A Decision Whose Time Has Come." The report recommended that the U.S. should switch to the metric system deliberately and carefully through a coordinated national program, and establish a target date 10 years ahead. In 1992 NIST the National Institute of Sciences (The Successor to the National Bureau of Standards) published a report titled A Metric America: A Decision Whose Time Has Come - For Real (NISTIR 4858) June 1992. The US has spent over a century trying to switch to the metric system through a process of voluntary adoption.
The SI is without question more rational that the US Customary System and the British Imperial System on which the US system was based. But it has failed to gain acceptance in the US and its adoption in many other countries has been painfully slow. This is a classic example of the influence of network effects resulting in lock-in. But it is also an example of economic protectionism masquerading as defence of cultural heritage and patriotism. The adoption problems of the SI are not unique. When an established ontology is challenged by a newer ontology there will be resistance to the new ontology no matter how good it is. Ontologies are like Khunian Paradigms; new ontologies are resisted by those who have a vested interest in the old system. Ontologies, like jargon, can form barriers to market entry that effectively exclude potential competitors and protect established players. The benefits provided by these barriers can outweigh the benefits of adopting the new ontology. In such cases voluntary adoption will not occur. Establised players are acting out of self interest in resisting change.
Effective conversion from an old established ontology to a new replacement ontology requires more than encouragement it must be accompanied by coercion. In the UK enforcement of the metric system is proceeding through government mandated use in; the education system, the military, all government contracts and for all commerce. Government departments are also aggressively pursuing offenders like Tesco through the courts. This policy has generated a backlash. Groups like the BWMA are mounting popular resistance campaigns aimed at preventing change.
Building a great ontology is only the first step. Getting people to adopt it is far more challenging. Adoption is not driven by the merits of the new ontology alone. Enforcement is often required. The US will not become metric until congress is prepared to enact enforceable laws that mandate the use of the metric system.
Posted by John R. Harris at 07:53 PM | Comments (2) | TrackBack
December 11, 2003
Visualizing the Shrinking World
A corollary of the statement "Time is Money" is that things that cause time to be consumed are money as well - distance is related to time through velocity and information is related to time in the same way through bandwidth. Velocity is a crucial factor in determining the cost of exchanging physical goods and bandwidth is similarly crucial in determining in the cost of exchanging information. In both cases speed costs. The changing relationships between time, distance, information, and money are at the heart of today's globalization trends.
The cost of a 3-minute transatlantic phone call is an interesting metric since it fixes distance and the amount of information. The graph above comes from a presentation on Globalization by the World Bank. It clearly shows that the cost of a 3-minute call between New York and London has been decaying exponentially over 6 decades. In fact this metric has a half-life of about a decade.
But the graph does not show the impact of these changes. The following before-and-after diagrams come from Telegeography [via Matt Jones]. Both diagrams show the cost of a one minute phone call from the US. These diagrams literally replace distance with cost and graphically show how the world is "shrinking" from a cost of information exchange perspective.
Cost of a 1-Minute Call from the US 1994
Cost of a 1-Minute Call from the US 1998
An interesting fact that is not immediately apparent from these diagrams is that the 10-year half-life of transatlantic call costs, that remained steady for 6 decades, has collapsed in the last decade. Between 1990 and 1996 the cost of a 3-minute call from New York to London fell from about $3.50 to $0.30, which is an order of magnitude fall in half a decade. It seems that cell phones, deregulation, and the rise of the Internet have well-and-truly shattered the old pricing paradigm.
Posted by John R. Harris at 03:33 PM | Comments (0) | TrackBack
September 10, 2003
Economics and the Internet's Large-Scale Topology
Distribution of the Internet around the world. (Top) Worldwide router density map obtained using NetGeo tool to identify the geographical location of 228,265 routers mapped out by the extensive router level mapping effort of Govindan and Tangmunarunkit. (Bottom) Population density map based on the CIESIN's population data. Both maps are shown using a box resolution of 1 degree by 1 degree. The bar next to each map gives the range of values encoded by the color code, indicating that the highest population density within this resolution is of the order 10**7 people/box, while the highest router density is of the order of 10**4 routers/box. Note that while in economically developed nations there are visibly strong correlations between population and router density, in the rest of the world Internet access is sparse, limited to urban areas characterized by population density peaks.
This graph and the explanation above are taken from Modeling the Internet's Large-Scale Topology by Soon-Hyung Yook, Hawoong Jeong, Albert-Laszlo Barabasi. Department of Physics, University of Notre Dame, Notre Dame, IN 46556, USA.
The authors state that the performance of Internet protocols is greatly influenced by network topology. It is therefore important to build accurate models of the Internet in order to test new protocol designs. This paper explains their findings about the large-scale structure of the Internet. They document several significant findings that contradict existing models:-
- The distribution of nodes on the internet is fractal and is strongly correlated with the fractal distribution of humanity. In the past the distribution was thought to be random.
- The likelihood of two nodes being linked decays linearly in proportion to the distance between them. In many existing models this likelihood was thought to decay exponentially as the distance between nodes increased.
- Preferential attachment is the name for the process by which scale free networks are thought to grow. It assumes the probability that a new node will link to an existing node is related to the number of links the existing node already has. The results indicate that the rate at which a node increases its degree is linearly proportional to the number of links the node has.
The Authors then describe a mathematical model built on these findings and point out that the existing models of the internet do not fit well with their findings and are therefore of limited value.
This is great but I think the authors have missed the economic side of things. The graphs clearly show the Internet is related to population density but I would guess it is more closely related to wealth density. If a map of the earth could be drawn with 1 degree by 1 degree squares color coded by the product of GDP per capita and population density I think it would look much more like the Router density map than the population density map does. Some of the graphs I produced in this article hint at this kind of distribution. I think using a wealth density approach would link Internet growth to the ecomony and provide a much better model.
Posted by John R. Harris at 05:05 PM | Comments (0) | TrackBack
July 28, 2003
UN Commission on Human Rights Loses All Credibility
On 24 July 2003 Reporters Without Borders was suspended from the United Nations Human Rights Commission for one year. For details of why this injustice happened see my previous entry Farce at the United Nations Human Rights Commission. Reporters Without Borders have published a press release and a report on the commission's accelerating decline, entitled UN Commission on Human Rights Loses all Credibility. Wheeling and dealing, incompetence and non-action.
The results of the vote on the suspension of the consultative status of Reporters without borders :
In favour (27): Azerbaijan, Benin, Bhutan, Brazil, Burundi, China, Congo, Cuba, Egypt, Ethiopia, Ghana, India, Iran, Jamaica, Kenya, Libya, Malaysia, Mozambique, Nepal, Nigeria, Pakistan, Qatar, Russian Federation, Saudi Arabia, South Africa, Uganda, and Zimbabwe.
Against (23): Andorra, Australia, Chile, El Salvador, Finland, France, Georgia, Germany, Greece, Guatemala, Hungary, Ireland, Italy, Netherlands, Nicaragua, Peru, Portugal, Republic of Korea, Romania, Sweden, Ukraine, United Kingdom, and United States.
Abstentions (4): Argentina, Ecuador, Japan, and Senegal.
Taken from the Reports without Borders press release
It seems Argentina, Ecuador, Japan and Senegal were too spineless to even have an opinion! The report by Reporters Without Borders makes clear that the noble idea of the United Nations Human Rights Commission is far from it's ignominious reality.
Posted by John R. Harris at 09:41 PM | Comments (0) | TrackBack
June 12, 2003
Comparing National Economies and Corporations - Just how bad was Enron ?
Obviously it can't be done! It's like comparing apples and oranges. Corporate revenue and Gross National Income GNI don't measure the same thing. Double counting is the least of your problems. But plotting them on the same graph is interesting! It gives you a very approximate graph of financial influence for Nations and Corporations. The most recent freely available data is for 2001. So I merged the data from the World Bank and the Fortune Global 100 and then plotted it. And what did I find. Wow, the Enron debacle has to be the largest crime ever! Check this out...
Data Sources
The Fortune Global 500
The World Bank Data and Statistics
Posted by John R. Harris at 06:16 PM | Comments (3) | TrackBack
Farce at the United Nations Human Rights Commission
When the new Libyan president of the United Nations Human Rights Commission, Najat Al-Hajjaji, made her inaugural speech at the opening of the 59th session of the Commission in Geneva on 17th March 2003 she was interrupted by six activists from Reporters Without Borders who threw leaflets into the meeting room. (Reporters Without Borders are also known as Reporters san Frontieres or just RSF)
As a result the pressure group may have its UN consultative status suspended. The way this harsh punishment has been decided and the process that led to this decision is farcical and sets a precedent that should not be allowed to stand.
The chair of the United Nations Human Rights Commission Committee usually rotates between various regional groups. The regional group who's turn it is nominates someone and that person is unanimously elected by acclamation. At least that's the way it worked for 46 years until South African Sipho George Nene nominated Libyan Najat Al-Hajjaji for the job. The Americans were not happy with the choice due to Libya's poor human rights record and insisted on a vote. The charter of the commission required a secret ballot that was duly conducted on January 20th 2003.
The 53 members of the committee voted as follows.
- 33 In favor of Najat Al-Hajjaji as president
- 17 Abstained
- 3 Against
The Third World Network an independent non-profit network involved in issues relating to development and the Third World reported:
South Africa's Sipho George Nene, who had proposed the name of Ms. Najat Al-Hajjaji for the chair, in a statement before the ballot (which the US had requested) said that the Commission and the African Group had been placed in a difficult and unenviable position. It was regrettable that the US delegation had opted for the extreme method of demonstrating its non-endorsement of the African Group's candidate. The decision to propose Ms. Najat Al-Hajjaji's name had been taken by the highest political organ of the African Union. The group hence had no choice but to respond to the political challenge posed by the subjection of the election to a vote.
For 46 years, the tried and tested practice of the unanimous election of the Chair of the commission had contributed positively in setting a solid foundation for the proceedings of the Commission. This "reliable practice" had been violated today. But the African group hoped that this unfortunate act would not be emulated in the future. "The rights of regional groups to present candidates of their choice should be respected." Great efforts had been made to persuade the US to use other available methods to express its displeasure. But these had failed. The African group urged members to demonstrate their confidence in the tried and tested methods of the past by voting for the African candidate with a resounding majority.
Geneva, 20th January 2003 Chakravarthi Raghavan
On the 18th March 2003, one day after the leaflet throwing incident at the opening session, the American representative Jeane Kirkpatrick had the following to say
Some criticism aimed at the Commission overlooks positive steps taken in recent sessions, but the widespread overall impression shared by many is that too many serious and systematic abuses of human rights go unchallenged or even covered-up in this body. The practice of electing the Commission members from some of the world's worst human rights offenders is especially serious. The cynical resort to procedural tactics to avoid taking a position on human rights abuses has not gone unnoticed and is widely and rightly criticized.
The government and the people whom I have the privilege of representing want the Commission to keep the faith placed in it by the United Nations’ founders when they envisioned the prospect of a body devoted to the promotion and protection of fundamental human rights...
Address by Ambassador Jeane Kirkpatrick
Head of the U.S. Delegation to the United Nations Commission on Human Rights
Palais des Nations
March 18, 2003
As a result of the leaflet throwing incident Cuba called for the suspension of RSF's consultative status for one year. France called for no action to be taken and for due process to be followed which would allow RSF a chance to appear before the UN's Committee on Non-Governmental Organizations before any action was taken. The committee took a vote on the 20th May 2003. Of the 19 members the voting came out as follows
- In favor of a ban - China, Côte d'Ivoire, Cuba, Iran, Pakistan, Russia, Sudan, Turkey and Zimbabwe
- Abstained - Cameroon, Colombia, India and Senegal
- In favor of no action - Germany, Chile, the United States, France, Peru and Romania
No due process was permitted and RSF were not given a chance to appear before the committee. RSF have pointed out the considerable irony of this result in a press release on their website they say:
On May 30th 2003 Sergio Vieira de Mello, the UN High Commissioner for Human Rights, said he opposes any attempt to exclude Reporters Without Borders from the United Nations by challenging its current observer status. But he cautioned.
As you know, these decisions are not taken by us or by the UN secretary-general, but by a committee in New York that deals with such matters.
To take effect, the move to ban RSF must be endorsed by the UN General Assembly's Economic and Social Council, which will consider the proposal in Geneva between July 1st and 24th at the ECOSOC session. Who knows what is going to happen then? One thing seems certain to me the UN is broken, possibly beyond repair.
Posted by John R. Harris at 03:59 PM | Comments (4) | TrackBack
April 09, 2003
Redrawing the Pentagon's new Map
In 1999 Ryan McCormack and I wrote a marketing piece on Globalization for Sapient Corporation. Aimed primarily at raising awareness of the issues involved in building global Internet systems it also touched on national market analysis and selection. I was reminded of this diagram showing income and connectivity for every country in the world from that piece while reading various articles on US Foreign Policy recently. These articles included this piece called the Pentagons new Map by Dr Thomas P.M. Barnett a US military Strategist on Globalization and US Foreign Policy and this more jaundiced view from the Washington Monthly.
Basically I think Dr Barnett is on to something when he claims that "disconnectedness defines danger".
Show me where globalization is thick with network connectivity, financial transactions, liberal media flows, and collective security, and I will show you regions featuring stable governments, rising standards of living, and more deaths by suicide than murder. These parts of the world I call the Functioning Core, or Core. But show me where globalization is thinning or just plain absent, and I will show you regions plagued by politically repressive regimes, widespread poverty and disease, routine mass murder, and "most important" the chronic conflicts that incubate the next generation of global terrorists. These parts of the world I call the Non-Integrating Gap, or Gap.
Having said I think Dr Barnett is on to something I don't think his conclusions are correct! He makes three mistakes;
1. He confuses poverty with danger. Deliberate disconnectedness is dangerous for everyone, whereas poverty is only dangerous for the poor. Lumping the poor and the dangerous together is callous.
2. He attempts to define a contiguous geographic region of the World that he calls the "Non Integrating Gap".
In this regard he makes a fundamental mistake. Conectedness is a network property and networks are fractal not contiguous. There is no contiguous region that is disconnected. Within each disconnected country there are islands of connection and within each connected country there are islands of disconnection. This is true at all levels, continents, nations, regions, cities, and companies, right down to individuals. There are terrorist cells in US cities fighting to disconnect the world and Journalists with satellite cell phones in remotest Afghanistan, Iraq, and Somalia working to connect everything.
3. A corollary of the contiguous region hypothesis is the idea of seam states that buffer the integrated core from the non integrating gap. As there is no contiguous region there can be no border, or rather the border is infinitely long. Either way the concept of Seam States is meaningless.
Income and Connectivity
I believe a better analysis can be produced by considering relative income and connectedness. I used per capita income as calculated by the World Bank and the number of Internet hosts as counted by the Internet Software Consortium (see assumptions). By plotting these two factors against each other for every national economy a picture emerges. Not surprisingly there is a correlation between these two factors - richer countries tend to have greater connectivity. But countries also tend to cluster by geographic region. The graph below clearly shows clustering of Sub Saharan African, Middle Eastern and North African and European economies. Over time economies tend to move to the top right of the graph - they increase per capita income and Internet penetration. The rate at which they move seems to be determined by their per capita income. Wealthy countries can adopt the Internet more quickly than poor countries. But there does seem to be a limit to the speed with which a country of a given per capita income can adopt the Internet. Most countries seem to move at this limiting speed and so a wave front of countries seems to have developed all rushing as fast as they can afford toward greater connectivity and wealth. One interesting feature of this graph is the countries that are not in their expected place on the wave front. It is these countries that are the subject of rest of this article.
The Outlier Economies
The graph above identifies several exceptional economies. These economies do not behave according to type. They are significantly different from their neighbors. They are outliers, islands of relative connectivity in a sea of disconnection like Israel, South Africa, and Kuwait or the reverse such as Burundi, Ethiopia, and Yemen. For example Israel, unlike it's middle eastern neighbors behaves like a European economy with respect to income and connectivity, South Africa is significantly more connected and wealthier than the rest of Sub Saharan Africa. While Kuwait and Yemen show opposite extremes, one enjoys fabulous wealth while the other suffers crushing poverty. These outlier economies are similar to Dr Barnett's seam states, however they do not surround anything in fact they are themselves surrounded. As a result of their isolated status they tend to get involved in conflict with their neighbors.
The Reluctantly Connected Economies
There are many economies that are unable or unwilling to achieve levels of connectivity that economies with similar incomes manage to sustain. These economies fall behind the wave front, they are the reluctantly connected. There is a significant risk that these economies will backslide and become disconnected. Preventing this backsliding and ensuring these nations realize the full benefits of connectivity should be a major objective of the connected world.
The Disconnected Economies
Finally there are economies that could not be plotted on these graphs because the necessary data are unavailable. I believe these fall into three main categories. There are a few dependant territories like the Faroe Islands, Guam, and Greenland that can be discounted because their data are included in other economies. Then there are the economies disconnected by paranoia, fear and hatred and finally the economies disconnected by secrecy. The table below is ordered by population size and shows a fairly clear division. The larger states are the pariah states - dangerous, paranoid and in some cases anarchic states that refuse to publish economic information even if they have the capability to gather the data. The smaller states are the hear-no-evil, see-no-evil, speak-no-evil bankers, protecting their clients and their own economies. These offshore tax havens and centers of secretive banking often serve the pariah states, and their corrupt leaders. Both these types of economies are dangerously disconnected. The world would be a far better place if they became fiscally transparent, connected economies.
| Economy | Hosts | GNI (Atlas Method $) | Population (1000s) | Status |
|---|---|---|---|---|
| Congo (Democratic Republic) | 113 | 0 | 52360 | Pariah State |
| Myanmar | 2 | 0 | 48315 | Pariah State |
| Sudan | 0 | 330 | 31687 | Pariah State |
| Afghanistan | 2 | 0 | 27248 | Pariah State |
| Iraq | 0 | 0 | 23750 | Pariah State |
| Korea, Dem. Rep. | 0 | 22384 | Pariah State | |
| Syrian Arab Republic | 0 | 1000 | 16593 | Pariah State |
| Cuba | 848 | 0 | 11222 | Pariah State, hold over from the cold war |
| Senegal | 480 | 9769 | No Internet Host count available | |
| Somalia | 1 | 0 | 9089 | Pariah State, Anarchic |
| Haiti | 0 | 480 | 8114 | Pariah State |
| Benin | 0 | 360 | 6437 | No Internet Hosts in 2001 |
| Libya | 59 | 0 | 5410 | Pariah State |
| Nicaragua | 1655 | 0 | 5202 | |
| Puerto Rico | 1667 | 0 | 3950 | US Dependent Territory |
| Liberia | 0 | 0 | 3216 | Pariah State |
| West Bank and Gaza | 1350 | 3091 | Dependent Territory, Pariah State, Emerging Nation ? | |
| United Arab Emirates | 29029 | 0 | 2976 | Fiscally Secretive |
| Oman | 646 | 0 | 2452 | Fiscally Secretive |
| Qatar | 0 | 0 | 598 | Fiscally Secretive |
| Equatorial Guinea | 0 | 700 | 469 | Pariah State |
| Brunei | 4398 | 0 | 345 | Fiscally Secretive |
| Netherlands Antilles | 104 | 0 | 217 | Dutch Dependent Territory, Fiscally Secretive |
| St. Lucia | 3970 | 158 | Fiscally Secretive | |
| Guam | 149 | 0 | 157 | US Dependent Territory |
| Channel Islands | 0 | 149 | UK Dependent Territory | |
| Mayotte | 0 | 0 | 145 | French Dependent Territory |
| Virgin Islands (U.S.) | 58 | 0 | 122 | US Dependent Territory |
| St. Vincent and the Grenadines | 2690 | 116 | Fiscally Secretive | |
| Aruba | 785 | 0 | 104 | Dutch Dependent Territory, Fiscally Secretive |
| Isle of Man | 116 | 0 | 75 | UK Dependent Territory |
| Northern Mariana Islands | 13 | 0 | 72 | US Dependent Territory |
| Andorra | 876 | 0 | 67 | Fiscally Secretive |
| American Samoa | 915 | 0 | 65 | US Dependent Territory |
| Bermuda | 4892 | 0 | 63 | UK Dependent Territory, Fiscally Secretive |
| Greenland | 2229 | 0 | 56 | Effectively a Dutch Dependent Territory |
| Faroe Islands | 1588 | 0 | 45 | Dutch Dependent Territory |
| St. Kitts and Nevis | 6880 | 41 | UK Dependent Territory | |
| Cayman Islands | 533 | 0 | 35 | UK Dependent Territory, Fiscally Secretive |
| Liechtenstein | 762 | 0 | 32 | Fiscally Secretive |
| Monaco | 434 | 0 | 32 | Fiscally Secretive |
| San Marino | 673 | 0 | 27 | Effectively an Italian Dependent Territory |
| Timor Leste | 6 | 0 | 0 | Emerging Nation, Destitute |
Assumptions and Sources
All the data used was for 2001.
I assumed that the number of hosts that use the assigned Top Level Domain (TLD) for a given country is an excellent indicator of the connectedness of that country. I believe this because hosts (computers) themselves are tradable commodities that must be purchased from abroad and that connection to the Internet is a very real sign that someone in a country wants to realize the benefits of connection to a global communication medium. Data for the number of hosts per country came from the Internet Software Consortium July 2001 Survey. Assuming Top TLDs actually map to countries leads to errors. In particular for the US since very few US hosts actually use the US domain. I totaled the following TLDs to get values for the US (net, com, edu, org, mil, us, arpa, gov, unknown). This of course is incorrect but I assumed it would tend to boost the US values higher and reduce the values for all other countries proportional to the number of hosts in the country. Three TLDs were ignored (int, biz, info), they have so few host that would make no difference anyway.
Data from the World Bank was used for population values and per capita income.
I have not produced charts for all regions of the world. Here is the zipped excel spread sheet I used. Feel free to play with these data yourself. I'd be interested in seeing what you come up with.
Posted by John R. Harris at 02:59 PM | Comments (1) | TrackBack
February 23, 2003
The Mobile Lounges at Dulles International Airport
Recently, I have been traveling to Washington D.C. via Washington Dulles International Airport and have begun to appreciate the fine architecture of the airport. Built between 1958 and 1966 by the engineering firm of Amman and Whitney the terminal building, control tower, and service buildings were designed by Architect Eero Saarinen who claimed it was "the best thing I have ever done."
This was the first US airport designed for jets and so there was no precedent for Saarinen to follow. One of the most distinctive features of the airport was the lack of any building extensions onto the airfield for aircraft loading. Instead passengers traveled from the terminal to their planes, which could be waiting over a mile away, on strange vehicles called Mobile Lounges and Plane-Mates. Saarinen viewed these mobile lounges as an extension of the airport. They were mobile buildings that served as transportation. Apparently when the lounges were first introduced they had a bar onboard and it was possible to drink cocktails while being transported to your plane!
A Mobile Lounge
Mobile lounges were constructed by the Chrysler Corporation in association with the Budd Company. They are 54-foot long, 16-foot wide, 17 1/2-foot high, and were originally specified to carry 102 passengers, 71 of them seated, directly from the terminal to the aircraft on the ramp. This was intended to protect the passengers from weather, jet noise and blast, and also eliminate long walking distances. Passengers had to walk only 200 feet once they entered the terminal until they were seated in the lounge for the short trip directly to their aircraft.
A Plane-Mate
These vehicles are still in operation at the airport today. The Mobile Lounge / Plane-Mate system seems to work very well. It has allowed the airport to grow at phenomenal rates - just over 25% in 1999. I am curious why the system never caught on. It obviously works, but miles of terminal buildings with endless moving walkways leading to telescopic boarding ramps have become the norm - Why? The only thing I can think of is that the operation costs of a Mobile Lounge system are high and the benefits, like support for airport expansion, are long-term. As a result they may fair badly when compared with the moving walkway systems that I imagine are cheaper to operate if inflexible.
In 1999 the Airports Authority Board of Directors approved the concept for an underground rail system on the airport that will eventually replace the current Mobile Lounges. So, sadly the Mobile Lounges are on their way out. However if you want to see what the future looked like in the late 1950's theres still time. And, if you're really inspired, the Airport Authority is currently advertising for Mobile Lounge and Plane-mate operators, pay is between $14.95 and $19.41 an hour and the job description is bizarre to say the least!
In mating with aircraft, employs appropriate operating procedure in keeping with the characteristics of the aircraft (e.g., location of projecting fins and sensors), preferred policy of the particular airline and the structure of the lounge.
Posted by John R. Harris at 11:21 PM | Comments (10) | TrackBack
December 31, 2002
A Solution for Managing Timezones, Times, and Dates in International Internet Systems
The measurement and management of time is something most people give little thought to. But when designing Internet based systems time presentation, manipulation and management can rapidly become a major headache. Just when you think youve got it nailed some other unanticipated problem arises. The regular failure of systems designers to get this right is a classic example of the principle of inappropriate parsimony.
The world is a sphere that rotates on its axis once every 24 hours and takes 365 days to rotate around the sun, more or less. Its very simple. But, the more or less part is vitally important. The world is not actually a sphere it is an oblate spheroid. It does not rotate every 24 hours it takes a ever-so-slightly longer than that and its getting slower, it wobbles on its axis which by the way is inclined to the plane of its rotation around the Sun. And as we all know it takes about a 1/4 of a day longer than a year to rotate around the Sun, more or less, and this time period is also increasing. Add to this the vagaries of international politics, national pride and public safety and you have a pretty complex system. All these factors affect the measurement and management of time. Given this complexity its not difficult to see why system designers try to simplify the conceptual model of the real world on which they base their solutions. However, this is the wrong thing to simplify. The solution can and should be simplified but the conceptual model on which it is based must be high fidelity not an approximation.
Time measurement in the real world
International Time Zones
Imagine the earth as a giant orange with 24 equally sized segments. Each segment takes up 1/24th of the earths circumference at any latitude. If two observers are standing on the same line of latitude, for example the equator, and they are exactly one segment (15 degrees) apart then there will be one hour difference between each observers local time. One of the observers will experience midday exactly 1 hour before the other. If the observers are exactly 2 segments apart then there will be 2 hours difference and so on.
By international treaty these segments are called international time zones. The first segment is called UTC-0 and is centered in the Greenwich Meridian that passes through both poles and Greenwich in London, England. This is the 0 degree line of longitude. International Time Zones are numbered, east of London they are positive and west of London they are negative as follows.
(.... UTC-3, UTC-2, UTC-1, UTC0, UTC+1, UTC+2, UTC+3.....)
In case you were wondering UTC-12 does not exist it is called UTC+12. The numbers refer to the offset in hours from the Greenwich Meridian. So UTC-8 is 8 hours behind UTC0. The time in the UTC0 time zone is considered to be the "base" time. All other times are relative to UTC. UTC stands for Coordinated Universal Time or just Universal Time. (Yes! the Acronym has the letters the wrong way round. The French insisted on having it that way!). "Greenwich Mean Time" is no longer the international base time it has been replaced by UTC.
The main point to understand is that each International Time Zone defines a precise geographical area of the earth's surface and an offset in hours from Universal Time. Each area is exactly 15 degrees wide, they cut across countries without regard to national borders or the decisions of local governments. But we all know that time often changes as we cross state borders not as we cross some arbitrary line defined by geometry. So what is going on? Thinking of International Time Zones as geometrically rigid is not a common practice as this map shows. Most people and even organizations confuse International Time Zones with Local Civil Time Zones. Even the name of this map is oxymoronic. There is nothing "standard" about the areas it defines, they change regularly forcing the map to be redrawn on a yearly basis.
Local Civil Time
Each country in the world, and sometimes each administrative subdivision within a country, aligns itself with an International Time Zone and bases it's own definition of Civil Time on this alignment. Choosing which International Time Zone to align with involves the evaluation of several factors; Maximizing useful daylight hours, the Time Zones chosen by trading partners, national pride etc.
For Example the west coast of North America including administrative sub-divisions in Mexico, the USA (but not Alaska) and Canada have all aligned themselves with the UTC-8 International Time Zone even though the west coast of Canada lies mostly in the UTC-9 International Time Zone. The result is a region with the same offset in hours from UTC running from the Yukon Territory of northern Canada to half way down Baja California, Mexico. Each country and subdivision has named its Local Civil Time; in Canada it is called Pacific Time as it is in the USA but in Mexico it is called America/Tijuana Time.
Countries cannot arbitrarily redefine or rename International Time Zones all they can change is their own definition of Local Civil Time. So Local Civil Time in India is defined as being 5 ½ hours ahead of Universal Time. This is convenient for India because of it's geographical location (straddling the boundary between UTC+5 and UTC+6) but there is no International Time Zone called UTC+5.5.
Much confusion results from the naming of International Time Zones UTC+3 is the name of a geographical area that is 3 hours ahead of Universal Time. However the name is also convenient shorthand for the offset from Universal Time. This leads many people to concluded that UTC+5.5 is the name of an International Time Zone. While it is plausible it is not accurate. There are only 24 International Time Zones.
Daylight Saving
Daylight Saving is the process of changing Local Civil Time, by adding or subtracting a fixed time period, usually and hour. This adjustment is carried out seasonally and has the effect of extending the amount of daylight available during the standard 9-5 working day. It has been shown that this simple adjustment can save lives by allowing people to travel to and from work during daylight hours. Continuing the example above there are two versions of US Pacific Time, Pacific Standard Time and Pacific Daylight Time. Pacific Standard Time is UTC -8 hours. But Pacific Daylight time is UTC -8 hours, + 1 hour, (effectively UTC -7 hours).
In the Northern Hemisphere the switch to daylight savings usually happens on the first Sunday of April at 2 am by adding one hour. The switch back usually occurs the on last Sunday of October again at 2 am by subtracting one hour. In the southern hemisphere everything is reversed. Daylight saving starts in September or October and ends in March or April.
From a systems design view point handling International Time Zones and Daylight saving is tricky. The end of daylight saving is the most disruptive time. Since the same hour is repeated. This can lead to severe problems if datestamps are recorded using Local Civil Time. Many designers do not realize that the system works differently in the northern and southern hemispheres, and Designers often assume that International Time Zones are the same thing as Local Civil Time.
Leap Years and Leap Seconds
Everyone knows that there are 365 days in a year, but every 4 years the Gregorian calendar makes a correction by adding an extra day because there are actually 365.25 days in a year. But this itself is merely an approximation. The rule for leap years is if it is divisible by 4 unless it is also divisible by 100 unless it is also divisible by 400 in which case it is a leap year again (So the year 2000 was a leap year!)
Every now and then leap seconds are added or taken away from UTC. This is achieved by adding, or subtracting, a second from the last minute, of the last day, of June or December. The last minute of 1996 was 61 seconds long. The reason for this adjustment is complex. If you want to understand then you need to look up the difference between International Atomic Time and Coordinated Universal Time. So far all leap seconds have been positive additions.
Recording Dates and Times for Internet Systems
One clean solution to the above problems is as follows
- All Times must include the date as well since, as you will see, the date can change depending on where we choose to display the time.
- All Times are recorded in UTC.
- All Times are recorded with the Name of the local Civil time used to record them and a few denormailzed attributes (Offset and Daylight Savings) for efficiency.
In this example dates are formatted as follows YYYY-MM-DD and all times are 24HR:MM:SS. This is how you would record 10 pm on May 18th 2002 in San Francisco
| UTC | Civil Time | Offset from UTC | Daylight Saving |
|---|---|---|---|
| 2002-05-19 5:00:00 | Pacific Daylight Time | -8 | +1 |
Notice that the days are different. In San Francisco it is still the 18th but at Greenwich it is the 19th. The benefit of this way of recording dates is that all dates recorded anywhere in the world can be compared. Since they are all recorded in UTC we can order by the UTC value and get everything in chronological order. Furthermore we can recreate the format of the original entered date and time easily and any other Time Zone without too much trouble.
2002-05-19 5:00:00 Subtract 8 hours and then add 1 hour = 2002-05-18 22:00:00 (Pacific Daylight Time)
This even gives us a way to untangle switches from daylight saving back to normal time. Consider the following. (Remember the switch from Daylight Saving back to Pacific Standard Time happened at 2 am on October 27th)
| UTC | Civil Time | Offset from UTC | Daylight Saving | Time in San Francisco |
|---|---|---|---|---|
| 2002-10-27 09:30:00 | Pacific Daylight Time | -8 | +1 | 2002-10-27 02:30:00 (Pacific Daylight Time) |
| 2002-10-27 10:30:00 | Pacific Standard Time | -8 | +0 | 2002-10-27 02:30:00 (Pacific Standard Time) |
This demonstrates why recording UTC is essential to avoid repeating the same timestamps when switching from daylight savings back to normal time.
What this model lacks is a way to lookup when daylight saving comes into effect. For this a lookup table is required as follows
| Civil Time Lookup Table | |
|---|---|
| Column Name | Example Value |
| Year | 2002 |
| Local Civil Time Name | Pacific Time |
| Country | USA |
| Administrative Subdivisions | Oregon, Washington, California |
| Daylight Saving Time Name | Pacific Daylight Time |
| Daylight Saving Time Offset | +1 |
| Daylight Saving Time Start | 2002-04-07 10:00:00 UTC-0 |
| Daylight Saving Time Stop | 2002-10-27 09:00:00 UTC-0 |
| Standard Time Name | Pacific Standard Time |
| Standard Time Offset | 0 |
| International Time Zone Name | UTC-8 |
| Offset from UTC | -8 |
When recording a time with this model you need to know the date and time and the civil time that is being used. Then a check on the lookup table can be used to set the required parameters such as offset and the daylight savings value. This is not particularly efficient since it requires a lookup every time a date-time is recorded.
Finally if you are going to all this trouble you really need access to a reliable system clock for accurate timestamps. This can be done by configuring Network Time Protocol.
There is one thing this model does not handle. In the event that a negative leap second is ever required this model will not work. The second in question will be repeated. This seems unlikely. Since the earth is slowing down in its rotation around the sun not speeding up.
Posted by John R. Harris at 03:36 PM | Comments (0) | TrackBack