Donnerstag, 8. November 2007

Shopping in Guangzhou

Shopping in Guangzhou
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Guangzhou offers a wide range of shopping experiences -- from department store and fashion boutiques to the strange world of traditional medicines and exotic foods.

For example, deep in Old Gunagzhou, the Qingping Market, north of Shamian Island, is the real deal in Asian shopping. It is a crowded, disorganized mass of stalls and shops that began to spring up with economic liberalization during the 1980's. While you can buy everything from antique porcelain to souvenirs of Chairman Mao, the area is famous (or infamous) for its variety of culinary "delicacies." Looking for some python steaks? How about dried rat meat, or stir fried crickets? Cats, dogs, birds, and bugs are all to be had here if you're brave enough...

Department Stores:

* Guangzhou Donshan Department Store - A large, modern store in the Dongshan District with an inventory of about 80,000 items ranging from electrical appliances to clothes.
* Nangfang Department Store - Established in 1954, the store has a national reputation and has chain stores in different sections of Guangzhou.
* Yong'an Company dates to 1947, making it one of the oldest department stores in Guangzhou. It is located at Shangxiajiu Road and Dishipu Road.
* The Friendship Store - One of the city's more modern and upscale retail outlets. It is located in the east of the city, on Taojin Lu. The store has five floors.
* The South Mansion Department Store - On Yanjian Xi Road.
* Xindaxin Company - Located on 4 Zhongshan Wulu. The 16-storeys include 15 shopping centers. If you can think of it, it's probably here. This list is by no mean comprehensive. Beijing Lualone has a number of different department stores between the Pearl River and Zhongshan Lu.

Perhaps the best shopping, though, is in the smaller and more traditional shops on the city's various shopping streets and markets. Beijing Lu has a number of these - trendy little boutiques pushing Hong Kong fashions. Most shops are open from 9am to 10pm.

Other shopping streets and markets include:

* Yide Lu - A number of large wholesale warehouses. Everything from children's toys to dried foods. Shops on the street also carry home decorations.
* Hai Yin Fabric Market - Located on Dong Hu Lu, this one of the largest markets in China.
* Qingping Market - land of the weird and wonderful. You can find a tea pot to take home. It is an amazing place to walk through! Handbags, shoes, and jewelry galore. But where else can you buy a live monkey? The market is a confusing maze of alleys and back roads next to Shamian Islands.
* Shamian Island - The island itself is a worthwhile place to shop. If you visit the island and Qingping you will grasp the contrast. Shamian Island is lined more with upscale boutiques.
* Night Markets - The best ones are on Xinhu Road or Jiaoyue Road. Last but not least, no shopping experience in Guangzhou is complete without a trip to Liwan Plaza. Restaurants, discos, boutiques and more: it is one of the biggest shopping complexes. The plaza is north of Shamian Island, between Changshou Lu and Xiajiu Lu.

Montag, 15. Oktober 2007

Pirate game

Pirate game

From Wikipedia, the free encyclopedia

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From Howard Pyle's Book of Pirates
From Howard Pyle's Book of Pirates

The pirate game is a simple mathematical game. It illustrates how, if assumptions conforming to a homo economicus model of human behaviour hold, outcomes may be surprising. It is a multi-player version of the ultimatum game.

Contents

[hide]

[edit] The Game

There are five rational pirates, A, B, C, D and E. They find 100 gold coins. They must decide how to distribute them.[1]

The Pirates have a strict order of seniority: A is superior to B, who is superior to C, who is superior to D, who is superior to E.[1]

The Pirate world's rules of distribution are thus: that the most senior pirate should propose a distribution of coins. The pirates should then vote on whether to accept this distribution; the proposer is able to vote, and has the casting vote in the event of a tie. If the proposed allocation is approved by vote, it happens. If not, the proposer is thrown overboard on the pirate ship and dies, and the next most senior pirate makes a new proposal to begin the system again.[1]

First of all, the pirates want to survive. Secondly, the pirates want to maximize the amount of gold coins they receive and, thirdly, they like throwing other pirates overboard.[1]

[edit] The Result

It might be expected intuitively that Pirate A will have to allocate little if any to himself for fear of being voted off so that there are fewer pirates to share between. However, this is as far from the theoretical result as is possible.

In the game theoretic analysis, the allocation offered by Pirate A that would be accepted (assuming all pirates are rational and are capable of understanding the scenarios that will occur when they accept/reject offers) is: Pirate A: 98, Pirate B: 0, Pirate C: 1, Pirate D: 0, and Pirate E: 1. [1]

This is apparent if we work backwards: if all except D and E have been thrown overboard, D proposes 100 for himself and 0 for E. He has the casting vote, and so this is the allocation.[1]

If there are three left (C, D and E) C knows that D will offer E 0 in the next round; therefore, C has to offer E 1 coin in this round to make E vote with him, and get his allocation through. Therefore, when only three are left the allocation is C:99, D:0, E:1.[1]

When B makes his decision, he knows this; he must therefore make sure that he is not thrown overboard. He does this by offering 1 to D. Because he has the casting vote, the support only by D is sufficient. Thus he proposes B:99, C:0, D:1, E:0.[1]

A, as a rational agent, knows that this is the allocation of coins if he is thrown overboard. He therefore offers A:98, B:0, C:1, D:0, E:1.[1]

Hence, the allocation accepted in each round is:[1]


Surprising to many, the end result is A: 98 coins B: 0 coins C: 1 coin D: 0 coins E: 1 coin

[edit] Extension

The game can easily be extended to up to 200 pirates. Ian Stewart extended it still further in the May 1999 edition of Scientific American (in particular to 500 pirates).[1]


[edit] See also


view Topics in game theory

Definitions

Normal form game · Extensive form game · Cooperative game · Information set · Preference

Equilibrium concepts

Nash equilibrium · Subgame perfection · Bayesian-Nash · Perfect Bayesian · Trembling hand · Proper equilibrium · Epsilon-equilibrium · Correlated equilibrium · Sequential equilibrium · Quasi-perfect equilibrium · Evolutionarily stable strategy · Risk dominance

Strategies

Dominant strategies · Mixed strategy · Tit for tat · Grim trigger · Collusion

Classes of games

Symmetric game · Perfect information · Dynamic game · Repeated game · Signaling game · Cheap talk · Zero-sum game · Mechanism design · Stochastic game · Nontransitive game

Games

Prisoner's dilemma · Traveler's dilemma · Coordination game · Chicken · Volunteer's dilemma · Dollar auction · Battle of the sexes · Stag hunt · Matching pennies · Ultimatum game · Minority game · Rock, Paper, Scissors · Pirate game · Dictator game · Public goods game · Nash bargaining game · Blotto games · War of attrition

Theorems

Minimax theorem · Purification theorems · Folk theorem · Revelation principle · Arrow's theorem

Samstag, 6. Oktober 2007

Samstag, 29. September 2007

Wikis

The Wide World of WikisPDF


For many, the wiki has been a surprise hit among the up-and-coming online publishing technologies. The radical concept of a website that anyone and everyone can edit was initially greeted by some with scepticism, but has rapidly proved itself to be a winner. The huge success of the online encyclopaedia Wikipedia (http://www.wikipedia.org) and the highly-publicised wrangles over its merits have propelled wikis into the media spotlight in recent months.

What’s a wiki?
A wiki is an open-access website that all-comers can view and edit, often without needing to register. The essential features are unrestricted editing by users, cumulative revision of articles rather than previous versions being deleted, and rapid quality checking (1). The basic philosophy of wikis involves harnessing the collective brain power of experts from around the world to continuously update and refine their content. Wiki systems encourage users to closely monitor changes, and present a forum for discussing inevitable clashes of opinion as and when they arise.


Box 1: Selected examples of science and technology wikis
*Cosmopedia (http://www.cosmowiki.org/index.php/Main_Page): a physical science resource and encyclopaedia that started in December 2005.
*EvoWiki (http://wiki.cotch.net/index.php/Main_Page): a free reader-built encyclopaedia of evolution, biology and origins, which aims to promote general evolution education, and to provide mainstream scientific responses to the arguments of creationism and other antievolutionists.
*Quantiki (http://cam.qubit.org/wiki/index.php/Main_Page): a free-content resource in quantum information science.
*Qwiki (http://qwiki.caltech.edu/wiki/Main_Page): a quantum physics wiki devoted to the collective creation of content that is technical and useful to practicing scientists in subjects including, but not limited to, quantum optics, quantum metrology, quantum control, quantum information and quantum computation.
*Wikiomics (http://wikiomics.org/wiki/Main_Page): a wiki for the bioinformatics community.

Some supporters have gone a step further when defining wikis, pointing out similarities with science itself. From this perspective, a wiki can be seen as a collaborative journey of a community of individuals with a shared passion, which self-corrects by peer review, and ultimately aims to explore and explain the world.

Wikis form part of the new generation of Internet technologies sometimes described collectively as ‘Web 2.0’. Central to the concept of Web 2.0 is user participation and the ‘radical trust’ required to entrust the production and control of information to the online community at large. Skeptics would point out that such trust replaces a decline in the traditional markers of credibility: the anonymity of the creators of the content of the new web, and its fluidity, means that verifying the source of the material, the date of its creation and assessing its objectivity become virtually impossible (2).

A brief history of wikis
Since the first wiki appeared in 1995, the technology has inspired an ever-growing body of private and public online knowledge bases (3). Wikipedia, which is probably the largest and best known, has mushroomed since its launch in 2001, and now includes almost 4 million entries in over 200 languages. The English-language version alone has more than 45,000 registered users, and up to 1,500 new articles were added daily during late 2005 (4).

The non-profit Wikimedia Foundation that hosts Wikipedia promotes many other wiki-based projects. These include the collaborative English-language dictionary Wiktionary (http://en.wiktionary.org/wiki/Main_Page), the Wikispecies (http://species.wikipedia.org/wiki/Main_Page) directory of life, and the Wikibooks (http://en.wikibooks.org/wiki/Main_Page) textbook collection. There is even an annual international wiki conference — with the next session to be held in Cambridge, Massachusetts, on 4–6 August (http://wikimania2006.wikimedia.org/wiki/Main_Page) — focusing on issues surrounding open-source software, free-knowledge initiatives and other wiki projects worldwide. Examples of further science and medicine wikis are listed in Box 1.

Wicked wikis
Despite the advantages of the wiki approach, it is clearly vulnerable to electronic ‘vandalism’ and problems with misleading content. Most wikis focus on the rapid correction of mistakes rather than their prevention, which allows users to introduce errors — albeit transiently — either by mistake or for their own dubious purposes (3).

Fighting wiki vandalism is an ongoing battle, and without adequate protection sites can easily become overwhelmed. In June 2005, the Los Angeles Times launched an innovative new online section, named the Wikitorial project, which allowed readers to rewrite its editorial column (5). The site was flooded with inappropriate material faster than the editors could remove it, and was shut down within days. Likewise, although most vandalism to Wikipedia is reportedly corrected within minutes (3), the site was forced to introduce a registration process for editors in December 2005 after detecting malicious changes to a biography (6) — a move seen by some as at odds with the basic wiki principle. Although new defences against vandalism are constantly evolving, deliberately inserted subtle errors continue to be the most problematic and insidious form of attack.

The thorny question of the accuracy of wikis recently hit the headlines when a bitter row erupted between two publishing giants, Nature Publishing Group and Britannica. An investigation carried out by Nature in December 2005 claimed that the scientific accuracy of Wikipedia did not substantially differ from that of the ‘gold standard’ reference work Encyclopaedia Britannica — clearly a great endorsement of the wiki principle (4). However, Britannica dismissed the Nature study as “misleading” and “completely without merit”, and called upon the journal to retract the “fatally flawed” report (7). Despite the surprising vehemence of this rebuttal, Nature has continued to stand by both its data and the conclusions of its report (8).

The issue of accuracy is clearly far from settled, but this clash illuminates the underlying concern that wikis could eventually supersede traditional publishing formats. However, in reality, they are just one of many online technologies that are challenging existing publishing models. The concern over the accuracy of Wikis is also part of a wider debate about the reliability of information on the Internet, an issue that has existed since the inception of the web but that has grown more pressing with the potential for abuse of the radical trust invested in Web 2.0 partcipants. The Center for the Digital Future, which studies trends in Internet use in the US, has reported declining rates of accuracy in the information available on the web over the last three years, paralleled by an increasing tendency for users to mistrust information available online (9). Case studies of other participatory web technologies have also uncovered significant breaches of reliability: for example, a study of Amazon’s product reviews found that a large number had been copied wholesale between products (10).

This example raises another important issue, that of how participation in the new interactive web is controlled and manipulated. Despite Wikipedia’s open standards, the project is overseen by a number of staff editors who are responsible for removing inaccuracies and inappropriate entries. These editors are not required to identify themselves, and some argue that their control of the project extends beyond removing errors to enforcing ideological control by removing entries that they disagree with or even perpetrating slander against those that oppose them (11). The question of the boundaries between fact and opinion is a difficult one, and one that is bound to occur in some of the scientific wikis listed above: EvoWiki’s statement that it is intended to counter Creationism will no doubt come under fire from those who argue that the latter should be accorded respect as an explanation for the origin of mankind. While information can be accumulated as a collaborative venture, one of the problems of wikis is that they obscure differences of opinion (11). Science is about the culmulative production of information, but it is born from a process of ongoing debate, which can be lost in the homogeneity of the wiki format.

In their favour, wikis are free, have almost unlimited scope, are instantly updatable and carry interactive links to numerous other sources. Yet, at present, traditional books and journals are still perceived by most to be more authoritative and reliable.

A Wiki World?
Wikis clearly have the makings of high-quality global resources if the issues surrounding vandalism and accuracy can be settled. The calibre of the individuals contributing to and monitoring wiki entries will also remain of paramount importance, as recognized in Nature’s call for researchers to contribute their expertise in order “to push forward the grand experiment that is Wikipedia, and to see how much it can improve” (12).

The scope of wikis is almost limitless and doubtless much of their potential remains untapped at present. However, during its short history, Wikipedia has achieved massive popularity as an online information resource — ranking 17th among the global top 500 most-visited websites according to the Alexa web-ranking service (http://www.alexa.com/site/ds/top_500) in April 2006. Time will tell whether wikis will co-exist alongside established information resources or whether the future will see a truly wiki world.

References
1. Guest, D. G. (2003) Four futures for scientific and medical publishing. It’s a wiki wiki world. British Medical Journal 326: 932.
2. Shaker, Lee. (2006) In Google we trust. First Monday, 11 (4) URL: http://firstmonday.org/issues/issue11_4/shaker/index.html
3. Wikipedia. Entry for Wiki (last modified 11 April 2006) http://en.wikipedia.org/wiki/Wiki.
4. Giles, J. (2005) News. Special Report. Internet encyclopaedias go head to head.
Nature 438: 900–901 (doi:10.1038/438900a) http://www.nature.com/nature/journal/v438/n7070/full/438900a.html.
5. Glaister, D. (22 June 2005) LA Times ‘wikitorial’ gives editors red faces. Guardian Unlimited http://technology.guardian.co.uk/online/news/0,12597,1511810,00.html.
6. Associated Press (5 December 2005) Wikipedia tightens the reins. Wired News http://www.wired.com/news/technology/0,1282,69759,00.html
7. Britannica (March 2006). Fatally flawed: refuting the recent study on encyclopedic accuracy by the journal Nature. http://corporate.britannica.com/britannica_nature_response.pdf
8. Editorial (30 March 2006) Britannica attacks... and we respond. Nature 440: 582 (doi:10.1038/440582b) http://www.nature.com/nature/journal/v440/n7084/full/440582b.html
9. Center for the Digital Future. 2005 Report. University of Southern California. http://www.digitalcenter.org/pages/current_report.asp?intGlobalId=19
10.David, Shay and Pinch, Trevor (2006). Six degrees of reputation: The use and abuse of online review and recommendation systems. First Monday, 11(3). http://www.firstmonday.org/issues/issue11_3/david/index.html
11. Andrew Orlowski (13 April 2006. A thirst for knowledge. Guardian Unlimited. http://technology.guardian.co.uk/weekly/story/0,,1752257,00.html
12. Editorial (14 December 2005) Wiki’s wild world. Nature (doi:10.1038/438890a) http://www.nature.com/nature/journal/v438/n7070/full/438890a.html

Mobile Web

Mobile Web

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Jump to: navigation, search
Pocket Internet Explorer displaying the Wikipedia main page on a PDA
Pocket Internet Explorer displaying the Wikipedia main page on a PDA
Opera Mini displaying the Wikipedia portal
Opera Mini displaying the Wikipedia portal

The Mobile Web refers to the World Wide Web as accessed from mobile devices such as cell phones, PDAs, and other portable gadgets connected to a public network. Access does not require a desktop computer.

Today, many more people have access to mobile devices than a desktop computer.

However, Mobile Web access today still suffers from interoperability and usability problems. This is partly due to the small physical size of the screens of mobile devices and partly due to the incompatibility of many mobile devices with not only computer operating systems, but also the format of much of the information available on the Internet.

Contents

[hide]

[edit] Standards

The development of standards is one approach being implemented to improve the interoperability, usability, and accessibility issues surrounding mobile web usage.

The W3C Mobile Web Initiative is a new initiative set up by the W3C to develop best practices and technologies relevant to the Mobile Web. The goal of the initiative is to make browsing the Web from mobile devices more reliable and accessible. The main aim is to evolve standards of data formats from Internet providers that are tailored to the specifications of particular mobile devices. The W3C has published guidelines (Best Practices, Best Practices Checker Software Tool) for mobile content, and is actively addressing the problem of device diversity by establishing a technology to support a repository of Device Descriptions.

W3C is also developing a validating schema to assess the readiness of content for the mobile web, through its mobileOK Scheme, which will help content developers to quickly determine if their content is web-ready. The W3C guidelines and mobile OK approach have not been immune from criticism and an alternative set of guidelines has been made available. This puts the emphasis on Adaptation, which is now seen as the key process in achieving the Ubiquitous Web, when combined with a Device Description Repository. An alternative approach is to adopt a Multi-Web Practice whereby for a given theme a set of URIs for different devices are developed with each URI having content appropriate to its designated device. A bookmark for this set of URIs held in an array is known as an AGI (Array of Graphic Identifiers)

mTLD, the registry for .mobi, has released a free testing tool called the MobiReady Report to analyze the mobile readiness of website. It does a free page analysis and gives a Mobi Ready score. This report tests the mobile-readiness of the site using industry best practices & standards.

Other standards for the mobile web are being documented and explored for particular applications by interested industry groups, such as the use of the mobile web for the purpose of education and training e.g. Standards for M-Learning Project.

[edit] Development

Evolution of mobile web standards
Evolution of mobile web standards

The Mobile Web primarily utilises lightweight pages written in Extensible Hypertext Markup Language (XHTML) or Wireless Markup Language (WML) to deliver content to mobile devices.

New tools such as Macromedia's Flash Lite or Sun's J2ME enable the production of user interfaces customized for mobile devices. In any case, with the increasing movement away from website-based content towards delivery via RSS, Atom and other formats in which content is divorced from presentation, the issue of microcontent becomes less of a problem as the device rather than the content-provider is enabled to specify how the content is displayed.

[edit] Top-level Domain

The .mobi sponsored top-level domain was launched specifically for the mobile internet by a consortium of companies including Google, Microsoft, Nokia, Samsung, and Vodafone. By forcing sites to comply with mobile web standards, .mobi ensures visitors a consistent and optimized experience on their mobile device.

[edit] Mobile Web 2.0

An example Web 2.0 technology used on the mobile web is the blog, resulting in the term moblog. Critics point to the difficulties of transferring Web 2.0 concepts such as open standards to the mobile web. On the other hand, advocates present it as a means of pushing information up onto the web in addition to bringing information down to the user.[1]

[edit] Faxing via Mobile Web

With the advancement of internet faxing, faxes are being sent online. Furthermore, they can be sent and received through Personal Digital Assistants (PDAs).

[edit] Advertising on the Mobile Web

Advertisers are increasingly using the mobile Web as platform to reach consumers. A recent study by the Online Publishers Association [2] reports that about one-in-ten mobile Web users said they have made a purchase based on a mobile Web ad, while 23% said they have visited a Web site, 13% said they have requested more information about a product or service and 11% said they have gone to a store to check out a product.

[edit] Limitations

Though internet access "on the go" provides advantages to many, such as the ability to communicate by email with others and obtain information anywhere, the web, accessed from mobile devices, has a large number of limitations. These include:

  • Small screen size - This makes it difficult or impossible to see text and graphics dependent on the standard size of a desktop computer screen.
  • Lack of windows - On a desktop computer, the ability to open more than one window at a time allows for multi-tasking and for easy revert to a previous page. On mobile web, only one page can be displayed at a time, and pages can only be viewed in the sequence they were originally accessed.
  • Navigation - Mobile devices do not use a mouselike pointer, but rather simply an up and down function for scrolling, thereby limiting the flexibility in navigation.
  • Types of pages accessible - Many sites that can be accessed on a desktop cannot on a mobile device. Many devices cannot access pages with a secured connection, Flash or other similar software, PDFs, or video sites.
  • Speed - On most mobile devices, the speed of service is very slow, often slower than dial-up internet access.
  • Broken pages - On many devices, a single page as viewed on a desktop is broken into segments, which are each treated as a separate page. Paired with the slow speed, navigation between these pages is slow.
  • Compressed pages - Many pages, in their conversion to mobile format, are squeezed into an order different from how they would customarily be viewed on a desktop computer.
  • Size of messages - Many devices have limits on the number of characters that can be sent in an email message.

[edit] References

This article was originally created and edited using the Web on mobile devices.

[edit] See also

[edit] External links

Personal digital assistant

Personal digital assistant

From Wikipedia, the free encyclopedia

Jump to: navigation, search
Look up Personal digital assistant in
Wiktionary, the free dictionary.
User with Treo (PDA with smartphone functionality)
User with Treo (PDA with smartphone functionality)

Personal digital assistants (PDAs) are handheld computers, but have become much more versatile over the years. PDAs are also known as pocket computers or palmtop computers. PDAs have many uses: calculation, use as a clock and calendar, accessing the Internet, sending and receiving E-mails, video recording, typewriting and word processing, use as an address book, making and writing on spreadsheets, scanning bar codes, use as a radio or stereo, playing computer games, recording survey responses, and Global Positioning System (GPS). Newer PDAs also have both color screens and audio capabilities, enabling them to be used as mobile phones (smartphones), web browsers, or portable media players. Many PDAs can access the Internet, intranets or extranets via Wi-Fi, or Wireless Wide-Area Networks (WWANs). Many PDA's employ touch screen technology.

Contents

[hide]

[edit] History

The term "personal data assistant" was coined on January 7, 1992 by Apple Computer CEO John Sculley at the Consumer Electronics Show in Las Vegas, Nevada, referring to the Apple Newton.

PDAs are some times referred to as "Palms", "Palm Pilot" or "Palm Tops" after an early PDA created by USR and Palm Inc called the Palm Pilot.

[edit] Typical features

Currently, a typical PDA has a touch screen for entering data, a memory card slot for data storage and IrDA, Bluetooth and WIFI for connectivity.

[edit] Touch screen

Many original PDAs, such as the Apple Newton and the Palm Pilot, featured touch screens for user interaction, having only a few buttons usually reserved for shortcuts to often used programs. Touch screen PDAs, including Windows Pocket PC devices, usually have a detachable stylus that can be used on the touch screen. Interaction is then done by tapping the screen to activate buttons or menu choices, and dragging the stylus to, for example, highlight. Text input is usually done in one of two ways:

  • Using a virtual keyboard, where a keyboard is shown on the touch screen. Input is done by tapping the letters.
  • Using letter or word recognition, where letters or words are written on the touch screen, and then "translated" to letters in the currently activated text field. Despite rigorous research and development projects, end-users experience mixed results with this input method, with some finding it frustrating and inaccurate, while others are satisfied with the quality.[1] Recognition and computation of handwritten horizontal and vertical formulas such as "1 + 2 =" was also under development.

PDAs for business use, including the BlackBerry and Treo, have full keyboards and scroll wheels or thumb wheels to facilitate data entry and navigation, in addition to supporting touch-screen input. There are also full-size foldable keyboards available that plug directly, or use wireless technology to interface with the PDA and allow for normal typing. BlackBerry also has additional functionality as push based email and applications.

Newer PDAs, such as the Apple iPhone include new user interfaces using other means of input. The iPhone uses a technology called Multi-touch.

[edit] Memory cards

Although many early PDAs did not have memory card slots, now most have either an SD (Secure Digital) and/or a Compact Flash slot. Although originally designed for memory, SDIO and Compact Flash cards are available for such things as Wi-Fi and Webcams. Some PDAs also have a USB port, mainly for USB flash drives.

[edit] Wired connectivity

While many earlier PDAs connected via serial ports or other proprietary format, many today connect via USB cable. This served primarily to connect to a computer, and few, if any PDAs were able to connect to each other out of the box using cables, as USB requires one machine to act as a host - functionality which was not often planned. Some PDAs were able to connect to the internet, either by means of one of these cables, or by using an extension card with an ethernet port/RJ-45 adaptor.

[edit] Wireless connectivity

Most modern PDAs have Bluetooth wireless connectivity, an increasingly popular tool for mobile devices. It can be used to connect keyboards, headsets, GPS and many other accessories, as well as sending files between PDAs. Many mid-range and superior PDAs have Wi-Fi/WLAN/802.11-connectivity, used for connecting to Wi-Fi hotspots or wireless networks. Older PDAs predominantly have an IrDA (infrared) port; however fewer current models have the technology, as it is slowly being phased out due to support for Bluetooth and Wi-Fi. IrDA allows communication between two PDAs: a PDA and any device with an IrDA port or adapter. Most universal PDA keyboards use infrared technology because many older PDAs have it, and infrared technology is low-cost.

[edit] Synchronization

An important function of PDAs is synchronizing data with a PC. This allows up-to-date contact information stored on software such as Microsoft Outlook or ACT! to update the database on the PDA. The data synchronization ensures that the PDA has an accurate list of contacts, appointments and e-mail, allowing users to access the same information on the PDA as the host computer.

The synchronizing also prevents the loss of information stored on the device in case it is lost, stolen, or destroyed. Another advantage is that data input is usually a lot quicker on a PC, since text input via a touch screen is still not quite optimal. Transferring data to a PDA via the computer is therefore a lot quicker than having to manually input all data on the handheld device.

Most PDAs come with the ability to synchronize to a PC. This is done through synchronization software provided with the handheld, such as HotSync Manager, which comes with Palm OS handhelds, Microsoft ActiveSync for older versions of Windows or Windows Mobile Center on Windows Vista, which comes with Windows Mobile handhelds.

These programs allow the PDA to be synchronized with a Personal information manager. This personal information manager may be an outside program or a proprietary program. For example, the BlackBerry PDA comes with the Desktop Manager program which can synchronize to both Microsoft Outlook and ACT!. Other PDAs come only with their own proprietary software. For example, some early Palm OS PDAs came only with Palm Desktop while later Palms such as the Treo 650 has the built-in ability to sync to Palm Desktop and/or Microsoft Outlook. Third-party synchronization software is also available for many PDAs from companies like Intellisync and CompanionLink. This software synchronizes these handhelds to other personal information managers which are not supported by the PDA manufacturers, such as GoldMine and Lotus Notes.

[edit] Customization

As with personal computers, it is possible to install additional software on most PDAs. Software can be bought or downloaded from the Internet, allowing users to personalize their PDAs to their liking. An example of this would be the display theme for the PDA. Almost all PDAs also allow for adding some form of hardware. The most common is a memory card slot, which allows the users to get additional and exchangeable storage space on their handheld devices. There are also miniature keyboards that can be connected to most mainstream PDAs for quicker text input. PDAs with Bluetooth use Bluetooth-enabled devices like headsets, mice and foldable Small Textkeyboard

[edit] Uses

PDAs are used to store information that can be accessed at any time and any where.

[edit] Automobile navigation

Many PDAs are used in car kits and are fitted with differential Global Positioning System (GPS) receivers to provide realtime automobile navigation. Most systems can also display traffic conditions, dynamic routing and roadside mobile radar guns.[citation needed] This information is usually downloaded from the Internet prior to travel, or can be downloaded on the fly with PDAs equipped with GPRS technology. Popular software in Europe for this functionality is TomTom software showing road conditions and 3D environments. PDAs are increasingly being fitted as standard on new cars.

[edit] Ruggedized PDAs

For many years businesses and government organizations have relied upon rugged PDAs for mobile data applications. Typical applications include supply chain management in warehouses, package delivery, route accounting, medical treatment and record keeping in hospitals, facilities maintenance and management, parking enforcement, access control and security, capital asset maintenance, meter reading by utilities, and "wireless waitress" applications in restaurants and hospitality venues. There are even PDAs designed to take significant amounts of punishment, probably meant for military use. Unfortunately, these devices often lack the features of other PDAs, and come with a steep price tag.[1]

[edit] Medical and scientific uses

In medicine, PDAs have been shown to aid diagnosis and drug selection and some studies have concluded that their use by patients to record symptoms improves the effectiveness of communication with hospitals during follow-up. The first landmark study in testing the effectiveness of PDAs in a medical setting was conducted at the Brigham & Women's Hospital and Massachusetts General Hospitals in affiliation with Harvard Medical School. Led by the team of Steven Labkoff, MD and Sandeep Shah, the Constellation project used Apple's Newton (first PDA in the market) to cater to the demands of the medical professionals.

Constellation's objective was to test how clinicians in various medical environments (wired vs un wired) would use medical reference books on a hand-held device. The study validated the hypothesis that PDAs with medical content would be used to a greater degree (>40% more often) in unwired environments.

Today, the company evolved from the effort Skyscape offers a wide range of resources including drug information, treatment options, guidelines, evidence based information and journal summaries including the drug & safety alerts. Other entrants include Epocrates and ABX guide, which supply drug databases, treatment information and relevant news in formats specific to mobile devices and services such as AvantGo translate medical journals into readable formats and provide updates from journals. WardWatch organizes medical records to remind doctors making ward rounds of information such as the treatment regimens of patients and programs. Finally, Pendragon and Syware provide tools for conducting research with mobile devices, and connecting to a central server allowing the user to enter data into a centralized database using their PDA. Additionally, Microsoft Visual Studio and Sun Java provide programming tools for developing survey instruments on the handheld. These development tools allow for integration with SQL databases that are stored on the handheld and can be synchronized with a desktop/server based database. Recently the development of Sensor Web technology has led to discussion of using wearable bodily sensors to monitor ongoing conditions like diabetes and epilepsy and alerting medical staff or the patient themselves to the treatment required via communication between the web and PDAs.

[edit] Educational uses

As mobile technology has become almost a necessity, it is no surprise that personal computing has become a vital learning tool by this time. Educational institutes have commenced a trend of integrating PDAs into their teaching practices (mobile learning). With the capabilities of PDAs, teachers are now able to provide a collaborative learning experience for their students. They are also preparing their students for possible practical uses of mobile computing upon their graduation.

PDAs and handheld devices have recently allowed for digital note taking. This has increased student’s productivity by allowing individuals to quickly spell-check, modify, and amend their class notes or e-notes. Educators are currently able to distribute course material through the use of the internet connectivity or infrared file sharing functions of the PDA. With concerns to class material, textbook publishers have begun to release e-books, electronic textbooks, which can be uploaded directly to a PDA. This eliminates the exhausting effort of carrying multiple textbooks at one time.

To meet the instructive needs sought by educational institutes, software companies have developed programs with the learning aspects in mind. Simple programs such as dictionaries, thesauri, and word processing software are important to the digital note taking process. In addition to these simple programs, encyclopedias and digital planning lessons have created added functionality for users.

With the increase in mobility of PDAs, school boards and educational institutes have now encountered issues with these devices. School boards are now concerned with students utilizing the internet connectivity to share test answers or to gossip during class time, which creates disruptions. Many school boards have modernized their computer policies to address these new concerns. Software companies such as Scantron Corp. have now created a program for distributing digital quizzes. The quiz software disables the infrared function on PDAs, which eliminates the element of information sharing among individuals during the examination.[2]

[edit] Sporting uses

PDAs are used by glider pilots for pre-flight planning and to assist navigation in cross-country competitions. They are linked to a GPS to produce moving-map displays showing the tracks to turn-points, airspace hazards and other tactical information.

[edit] Technical details

[edit] Architecture

Many PDAs run using a variation of the ARM architecture (usually denoted by the Intel XScale trademark). This encompasses a class of RISC microprocessors that are widely used in mobile devices and embedded systems, and its design was influenced strongly by a popular 1970s/1980s CPU, the MOS Technology 6502.

[edit] OS

The currently major PDA operating systems are:

[edit] Decreasing popularity?

PDA sales fell 43.5% from 2006 to 2007. Approximately 4 million PDAs are sold per year, while smartphone sales are approximately 60 million per year.

According to a Gartner market study, the overall market for PDAs grew by 20.7% in the third quarter (Q3) of 2005, compared to Q3 2004, with marketshare resolving as follows (by operating system):[citation needed]

[edit] Shortcomings

Perhaps, more than any other computer devices, the PDA lacks the fully-blown infrastructure of a Wireless Broadband network. This could be offered in future by WiMax. Nowadays prices of laptops are coming down. Though somewhat bigger in size, laptops have better visibility and are more powerful. However, the OQO Model 2 has been released as an IBM-PC compatible PDA with a USB port so that people can play computer games from ubiquitous operating systems such as Windows XP and connect typical PC peripherals.

[edit] Popular consumer PDAs

[edit] Discontinued

[edit] Rugged PDAs for business, government and military applications

[edit] See also

[edit] References

  1. ^ HWR accuracy:

[edit] External links

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