Enabling the Internet of Things

COVER FEATURE OUTLOOK

Roy Want, Bill N. Schilit, and Scott Jenson, Google

Merging the virtual World Wide Web with nearby physical devices that are part of the Internet of Things gives anyone with a mobile device and the appropriate authorization the power to monitor or control anything.

he Internet of Things (IoT) paradigm enables including how to handle dramatic increases in network interconnectedness among devices—anytime, scale and how to determine device proximity, sometimes anywhere on the planet—providing the Inter- referred to as localized scalability.1 In an IoT world, pref- net’s advantages in all aspects of daily life. An- erentially discovering things nearby and letting users Talysts predict that the IoT will comprise up to 26 billion interact with them is a powerful mechanism for over- interconnected devices by 2020, a 30-fold increase from coming a global network’s scale and complexity. Other 2009 (www.gartner.com/newsroom/id/2636073).______important IoT enablers are peer-to-peer connections, The conventional Internet has proved valuable in allow-latency real-time interaction, and integration of de- most all endeavors by giving people the ability to inter- vices that have little or no processing capability. act with global information and services. The majority of this interaction happens through the World Wide Web, THE IOT VISION with client computers running a browser and communi- The Web provides an important interaction model for the cating with cloud-based servers. However, the Internet IoT by letting users get device-related information and in is not limited to the Web: a wide diversity of other pro- some cases control their devices through the ubiquitous tocols are employed to make use of global Internet con- Web browser. The conventional Web is a convenience we nectivity. The IoT is considered to be the next logical evo- enjoy as we search for information, respond to email, lution, providing extensive services in manufacturing, shop, and engage in social networking; the IoT would smart grids, security, healthcare, automotive engineer- expand these capabilities to include interactions with ing, education, and consumer electronics. Many of these a wide spectrum of appliances and electronic devices systems already have a Web presence but use protocols that are already ubiquitous in the early 21st century.2 that are largely Web independent. We refer to devices that are part of the IoT and directly Practical issues with the IoT vision must be addressed, accessed, monitored, or controlled by Web technologies

Client interaction with services

Cloud service Proxy Web service (for example, ftbit.com) (for example, movieposters.com)

as the Physical Web: Physical Internet cloud Web = Web technology + IoT. Identifers are the key to enabling any kind of interac- Reference: tion among devices. From an “Buy Movie Tickets” IoT perspective, IPv6’s 128-bit addresses serve as identifers Bluetooth for a global network of de- URI vices. Alternatively, Uniform NFC tag Resource Identifers (URIs), Bluetooth which include both locators (a) (b) LE tag and names, provide a higher- level concept that bridges FIGURE 1. Two methods for a smartphone to interact with the Internet of Things: (a) direct and those devices to existing Web (b) proxy. Networked computers can participate in the IoT—passive objects can, too. LE, low energy; technology. The Uniform Re- NFC, near-ﬁeld communication; URI, Uniform Resource Identiﬁer. source Locator (URL) is used in conjunction with a Distrib- uted Name Service (DNS) to route and Figure 1 shows the two distinct inter- major networking companies such connect to services. Uniform Resource action modes that smartphones can as Cisco and microprocessor gi- Names (URNs), such as globally unique enable in the IoT. Through direct in- ants such as Intel. It even serves as IDs, are resolved by scheme-specifc teraction, a smartphone can query the the title or theme of conferences, methods. A distinguishing aspect of state of an IoT device in its proximity such as the “Internet of Things” the Physical Web is to consider URIs as and then provide a bridge between low- World Forum (http://iotinternetof 3 the primary identifer. level peer-to-peer protocols, such as thingsconference.com).______Many researchers and practitioners Bluetooth or Wi-Fi, and Internet proto- However, the phrase represents in this feld, including the authors of cols, such as HTTP and TCP. One exam- ideas that have existed since the be- this article, expand the IoT defnition to ple is the Fitbit ftness monitor, which ginning of the Web or been written include enabling an Internet presence uploads a user’s step count through his about in whitepapers from well-known for any person, place, or thing on the or her phone over a 4G network to the research laboratories such as (Xerox) planet, thereby pushing our notion of user’s account in the cloud. Through PARC and HP Labs. So why isn’t the IoT the Physical Web beyond smart devices. proxy interaction, mobile users who a standard part of the way we do busi- Clearly, an Internet presence cannot happen to be near an IoT-enabled ob- ness today? Why is it still the subject occur without processing and network- ject or device can look up associated of speculation and vision statements ing, so instead of providing them di- information published by interested in keynote addresses at well-known rectly, an Internet service can provide parties through a Web service using computer industry events such as the information and perform actions via their smartphone, just as they would annual Consumer Electronics Show? other nearby devices serving as a gate- when performing a Web search. One The answer appears to be that the way to that proxy service.4,5 example is a movie poster that enables IoT exists for a small number of tech- Gateway devices will enable billions nearby people to automatically access a nologies that have the ingredients for of people, places, and things to partic- webpage on their smartphone and buy a successful business case. In general, ipate in the IoT—most people today electronic tickets online. these early systems have tended to already carry one. The smartphone, be closed ecosystems, using private the most popular computing device of DOES THE IOT APIs and locking up the data. This is all time, with more than 1 billion users ALREADY EXIST? counter to the spirit of open systems (www.idc.com/prodserv/smartphone The IoT is a popular buzzword in at the heart of the original Internet -os-market-share.jsp),______is well equipped the computing industry; it appears standards, refecting instead the to serve as this pervasive portal. in the marketing campaigns of more recent commercial successes of

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OUTLOOK

(a) (b) (c)

FIGURE 2. Various forms of electronic tags support the Physical Web (all about the size of a quarter): (a) a near-ﬁeld communication (NFC) tag; (b) a quick response (QR) code; and (c) a Bluetooth low energy (BLE) tag. However, it is not clear which technology—each with its own affordances and problems—will become the primary IoT enabler.

proprietary business entities such as wired or wireless connection to the that interfered with the wireless iden- Apple’s App Store and Facebook. You Internet, falling into the class of pas- tifcation process. can actually buy home automation sive devices. For these objects, a tag, The latest opportunity for RFID systems that connect to the Internet smartphone, and proxy Web service is technology is in the form of near-feld through your home’s Wi-Fi. These sys- needed to provide users with the ob- communication (NFC) as a support for tems are usually built with a bridge ject’s Web presence. Of all the vision- electronic payments. Although only a that controls the automation compo- ary ideas around the IoT, this one has small number of smartphone products nents through proprietary protocols made the least progress to date. include NFC transceivers, the potential on one side and communicates with for this capability to propagate to all fu- open protocols to a proprietary Web ENABLING TECHNOLOGIES ture smartphones is high. It would also service on the other. Users can then FOR THE IOT enable phones to read passive NFC tags employ desktop computers or smart- As Figure 2 indicates, tagging an ob- that can store a URI, while still being phones as a client to control their ject to reference a proxy Web service cheap, small, thin, and attachable to al- home by interacting with the Internet can be achieved through a variety of most anything. In September 2014, Ap- service, efectively providing user in- technologies, but the early primary ple announced the iPhone 6 would interface hardware at no cost to the IoT contenders have had issues that hin- clude NFC support for ApplePay. With device manufacturer. dered their adoption. Apple’s signifcant smartphone market A signifcant hurdle to fully re- share in the US, this move could infu- alizing the IoT relates to scale— RFID and near-ﬁeld ence other handset manufacturers to specifcally, expanding the Internet to communication follow suit, pushing NFC into becom- IoT scale means that the address space In the early 2000s, RFID was considered ing a key IoT enabler. for the Internet will need to increase one of the most likely technologies to by several orders of magnitude. There- accelerate the formation of the IoT.6 A Optical tags and fore, another requirement for support- new UHF RFID tag standard was devel- quick response codes ing the IoT is a larger device address oped by EPC Global (http://epcglobal Another contender for low-cost tag-

space than that provided by IPv4. To .org),___ with a goal of further automat- ging is the optical or printed tag—in enable this kind of expansion, the In- ing retail transactions and replacing particular, the most popular 2D op- ternet Engineering Task Force (IETF) barcodes with a tag that was machine tical standard, the quick response has been working on the IPv6 stan- readable at a distance of up to 10 feet. (QR) code.7 The success of the QR code dard for some time. When the tran- But after several trials with leading standard is directly related to the ubiq- sition is complete, the address space vendors such as Walmart and Tesco, uity of its reader, an application of the will be large enough to support every the EPC standard met with limited up- high-resolution camera found in all object on the planet, enabling embed- take principally because, in practice, a modern smartphones. A QR code is ex- ded computers of all sizes to be easily signifcant number of tags were unde- tracted and decoded from a scene using integrated into the Internet. However, tectable due to factors in retail envi- image-processing techniques yielding a large percentage of the objects in ronments such as poor product/tag ori- a number, text, or URI. QR codes are the IoT will not be suitable for direct entation and the presence of materials already printed on many products,

30 COMPUTER WWW.COMPUTER.ORG/COMPUTER______

IN THE PHYSICAL WEB, PEOPLE, PLACES, AND THINGS HAVE WEBPAGES TO PROVIDE INFORMATION AND MECHANISMS FOR USER INTERACTION.

including newspapers, magazines, bill- This new technology standard, proximity, and thus results could be boards, and coupons; they even appear along with the availability of inexpen- shown as lists, enhanced maps, or foor on prime-time television ads. sive BLE tag hardware and tag readers plans. Searching the physical Web at However, in practice, many QR ad- already integrated with smartphone home would bring up thermostats, vertising campaigns result in a poor hardware, has been a considerable cat- DVRs, TVs, home audio systems, rout- customer response. The reasons re- alyst in this space. Many established ers, and water and electrical meters as late to the requirement that a prein- computer companies, and a signifcant results. You might see a snippet and a stalled application is required to read number of startups, are experiment- link to the manual for a nearby micro- QR codes—which can be a barrier for ing with products and business oppor- wave oven, along with other links that some users—as well as difculty in po- tunities associated with these tags. control or provide information about sitioning the phone so that the camera As with the other tagging technology, devices in your house. There would be can focus and accurately decode the this is also an enabler for the IoT, but a lot to show, but no more than the re- image. Some advertisers also feel that with more opportunities for ubiqui- sults of any Web search today; search a visible QR code spoils the aesthet- tous deployment, higher-accuracy tag engines are good at ranking and pro- ics of their campaigns (https://www______reads, and the ability to blend in invis- viding the most relevant items frst. .techdirt.com/blog/wireless/articles ibly with a product. Webpages are a great technology

______/20120307/06130018010/qr-codes-ugly for human-to-machine (H2M) inter-

______-overused-doomed.shtml). THE PHYSICAL WEB action, but many use cases for the IoT In the Physical Web, people, places, are machine to machine (M2M). One Bluetooth low energy and things have webpages to provide solution that has already had great One of the more promising new tech- information and mechanisms for user success in combining human and nologies in the device tagging space interaction. The notion of open Web machine-readable content in open Web is Bluetooth low energy (BLE),8 part technologies as the bridge to the phys- technologies is the use of structured of the Bluetooth v4.0 standard (Blue- ical is not new: access points, routers, data embedded by webmasters into tooth Smart) and adopted by the Blue- solar panels, electricity meters, and their pages. The data formats used by tooth Special Interest Group in 2010. cofee shops have Web landing pages, Schema.org______and others let user agents Consequently, Bluetooth silicon for example. However, it is the breadth and cloud services act intelligently, vendors have included BLE in their and depth of the stack surrounding parsing data for events, organizations, latest chipsets, and all smartphones the Web that make this an appealing people, places, products, reviews, and released in the last few years have vision for the IoT’s evolution. To be so on and acting on them either in- BLE hardware, with various levels of sure, HTTP will not be an exclusive teractively or proactively. Structured capability depending on operating protocol for communication with data could also lead to more uniform system support. things in the same way that it is not an user interfaces across devices, so that Bluetooth silicon can be pared exclusive protocol for the Internet— when users learn one interface, they down to only include the BLE aspects there are plenty of use cases where do not have to relearn it for another of the standard, removing the need for Web protocols do not have the desired device—for example, setting the time compatibility with classic Bluetooth. properties, such as the Real-Time on an appliance that has a clock. This results in a small, low-cost silicon Streaming Protocol (RTSP). Open Web technologies, including implementation that can be used as a Like the conventional Web search HTML, Ajax, HTTPS, and OpenID, and low-power electronic tag. Tags based engine to which you submit a query structured data apply equally well to on BLE can signal their presence by and it returns text snippets and links the IoT. However the open Web does transmitting an advertising packet to relevant “things,” the Physical Web not have an efective mechanism for once per second at a power budget would return search results. However, locating objects in the physical world. that enables them to operate for up to because the IoT is the world that we One approach that looks particularly one year on a lithium coin cell battery can see, hear, and touch, search results appealing is the use of radio beacons (about the size of a US quarter, with would not only be ordered by conven- that broadcast URLs at very low power 240-mAh capacity). tional ranking algorithms but also by and over a small geographic radius.

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OUTLOOK

IoT IoT services services

Internet Internet cloud cloud

security, privacy, and cost. If interaction latency and connectivity are not a problem, cloud computing is an attractive paradigm. In recent times, the detrimental efect of malware on home computers has made the cloud even more attractive. Based on these observations, it seems like a good idea for the IoT archi- (a) (b ) tecture to register every device with a cloud service and communicate with FIGURE 3. Alternative approaches for the IoT. (a) Peer-to-peer, with gateway to an IoT that service alone. Users or other com- service); and (b) centralized IoT service. Because the IoT will connect many devices with puters would then interact with this constrained networking capabilities, P2P networking may become more prevalent and as service to determine the device’s sta- common as cloud-based solutions are now. tus or control its behavior. However, there are other factors to consider.

One of the frst projects to promote this today takes a centralized approach for Beneﬁts of peer-to-peer idea was HP’s Cooltown,3 which used its services, but it is not clear that this Although the cloud model is clean and infrared beacons to transmit URLs. makes sense for much of the IoT. Fig- straightforward, the requirements for More recently, BLE provides a similar ure 3 compares the approaches, with full Internet communication might be low-power beacon mechanism that cloud-based services representing the too costly or burdensome for what in can also integrate a URL emitted in centralized paradigm. many cases are simple low-performance short periodic advertisement packets devices. In practice, any hardware that (www.uribeacon.org).______Beneﬁts of cloud computing can connect directly to the Internet One way to bridge the gap between The computing world has shifted par- would require a physical Ethernet, Wi-Fi the physical and virtual is to attach adigms several times, from the cen- radio, or cellular modem, all of which beacons to all our objects. These bea- tralized mainframe computer to the elevate the device’s cost and power cons would broadcast a URL along with decentralized PC running standalone consumption. In practice, it might be other information to help with rang- applications back to today’s central- better to have one bridging device that ing. It sounds like a huge investment, ized cloud services. The computing supports Wi-Fi and enables simple pe- but beacons currently cost less than industry is gravitating toward more ripheral IoT devices to talk to the bridge. US$5, and the price is likely to drop, centralized cloud services primarily Many low-performance communication thus future manufactured “smart” because they are easier to manage. standards such as ZigBee, 6LoWPAN, objects are likely to integrate this ca- Advantages include the economics of Bluetooth Classic, and BLE have evolved pability. By utilizing proximity URL scale when building datacenters, auto- to fll that gap—with no clear winner. beacons, the potential for interacting matic backup of all data, and enforced As with the opportunity for tagging de- with the Physical Web is not only more physical security. However, modern vices, the new BLE standard could well practical, but has greater utility than client devices are both capable and fex- dominate this low-end space, but it will both NFC and QR codes. ible. Laptops utilize high-performance take time for this to play out. multicore technology, and even smart- IoT devices, unlike the traditional CLOUD COMMUNICATION phones contain powerful processors. Internet, beneft from the concept of VERSUS PEER TO PEER We have the option of running simple proximity as we described when intro- One of the long debates in computer clients connected to powerful cloud ducing the Physical Web. However, it science has been whether to build services or powerful local apps that run is not just the knowledge of nearby ob- centralized systems or to make them on their own. The decision comes down jects that is useful: colocated devices fully distributed. Much of the Web to our tolerance for tradeofs in latency, have the opportunity to cooperate

32 COMPUTER WWW.COMPUTER.ORG/COMPUTER______

THE LONG TAIL OF THE MANY POTENTIAL USES OF THE IOT CHALLENGES THE SCOPE AND BREADTH OF TODAY’S SMARTPHONE APPS.

with each other in real time and fulfll various ideas. One approach, called likely pass thousands of smart devices a task that would not be possible with edge computing, moves some of the every day, each one capable of interac- any single device.9 A simple example cloud processing closer to devices that tion. It does not scale to have to install is the sharing of peripherals. A com- require real-time interaction, thus re- an app before using each one. You will puter that fnds itself close to another ducing the number of network hops also likely want to delete apps as you device with a bigger and better screen and hence latency. An example of edge install others, because there will be could wirelessly share it, for example, computing is the cloudlet paradigm,10 many devices that you will interact to take advantage of its display when which provides a means of rapidly en- with only once. playing a movie. Likewise, a computer abling real-time services in the fxed This becomes even more evident could utilize a component that it does infrastructure to be used by mobile when you factor in how smart devices not have if it is wirelessly discovered devices, such as smartphones and will have a signifcant long-tail ef- on another nearby device—examples wearables, just one network hop away fect.11 Instead of a few big apps that include a sensor, camera, or mouse. using Wi-Fi. This is achieved through you use every day for many tasks, you Proximate sharing will be an im- a virtual machine (VM) running on a will have a huge range of small-device portant aspect of the IoT, but this will powerful nearby workstation, and dy- apps that ofer the tiniest of interac- not be easy to accomplish. Devices need namically provisioned with software tions, such as just controlling an on/ to discover each other, trust each other, and services customized for that ap- of switch. In fact, many devices will and then make a connection. Further- plication. When the task is complete, eschew interactivity all together and more, sharing is achieved by protocols the resources can then be freed up, only ofer a snippet of data, for exam- and data formats that need to be stan- allowing a new VM, or multiple VMs, ple, when the next bus is arriving. The dardized and supported by both ends to be instantiated on the cloudlet. A long tail of the many potential uses of the connection. In a world in which cloudlet lets IoT devices interact in of the IoT challenges the scope and there are many more commercial play- real time with cloud-like services, breadth of today’s smartphone apps, ers than in the early days of the Internet, even though they are far removed requiring only micro-interactivity or this becomes a difcult proposition. from a datacenter. micro-information. The traditional Internet has evolved a To enable this new Physical Web core set of standardized protocols, but WHAT THE IOT for the IoT, we need a way for any user, in the undefned IoT world, many stan- MEANS FOR APPS with any smartphone or tablet, to walk dards and proprietary solutions are still Today, any new IoT product almost al- up to any IoT device and interact with up in the air. To illustrate how difcult ways comes with a smartphone app to it (without a specialized app). We need this can be, consider the Digital Living control it. This is a consequence of two a richer extension of today’s Web, al- Network Alliance (DLNA; http://dlna dominant forces: native smartphone lowing each smart device to wirelessly ___.org), which was established to enable apps ofer the only practical means to broadcast a URL to its surroundings. multivendor consumer electronics to access and communicate with smart Proximity is the context that can be discover each other and share content devices, and there has been so much used to flter this to a tractable num- and services. To date, DLNA has only recent fnancial success with mobile ber, allowing any smart device to list been integrated with a small percent- apps that they are now expected. Peo- and then interact with other nearby age of networked products because, in ple assume that they will always use smart devices. This is the basis of a practice, larger companies are driven apps for every possible interactive ex- discovery service that is the best of by the fnancial rewards of dominating perience with IoT devices. today’s native and Web apps, creating a market with their own proprietary This approach unfortunately cre- a new platform, a type of interactive ecosystem. ates problems as the IoT landscape lingua franca allowing devices of any grows and matures. Although it is easy type to ofer data and interactivity to Hybrid IoT solutions to imagine a phone with a few dozen any other device. Innovative solutions to latency prob- applications on it, things become more The current model of native apps, lems associated with existing cloud- problematic with millions of IoT de- while quite popular, is not up to the based networking attempt to combine vices. In the very near future, you will task of supporting the many and

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OUTLOOK

varied use cases that the IoT will bring Context sensing a display, actuator, or switch can be about. We need to extend well-known One of the ways an application can controlled from a browser or through systems, such as the Web, to allow a perform more efectively is through a Web service, thus making it easy to signifcantly easier and more light- context awareness. Sensing what is integrate related information into weight approach for enabling devices around a host device (and its user) and control decisions. For example, emerg- to interact with one another. the context in which it is used allows ing Web-connected irrigation systems might provide an interface for specify- ing the plants in your garden and use Web services to determine expert wa- THERE IS A REASON PEOPLE ARE EXCITED tering recommendations. ABOUT THE IOT: IT FEELS LIKE A BIG Privacy and security OPPORTUNITY TO IMPROVE HOW WE One of the primary challenges for the DESIGN AND BUILD PRODUCTS. future will be avoiding the darker con- sequences of a world with globally connected devices. The Physical Web could enable hackers to control our de- FUTURE OPPORTUNITIES an app to adapt how data is presented vices unless precautions are taken. The AND CHALLENGES and fltered; consider, for example, a conventional Web already has security While the IoT applications will be local map application that automat- measures in place that can be applied to varied and difcult to predict, some ically shows the user’s current posi- the Physical Web, but it is unclear if these clear opportunities will arise for tion. The more context a device has, will be suitable or even adequate for all ubiquitous information gathering, the more likely it can automatically IoT applications. In addition to hacking, context sensing, and control, which provide a user with the required in- social threats can result when knowl- will likely be key enabling building formation. However, the worst thing a edge is leaked in unexpected ways. For blocks. However, some of the real context-aware application can do is in- example, knowledge that a house is in challenges will be in the areas of pri- fer something on behalf of a user that an energy-saving mode could be a good vacy and security. turns out to be wrong. The future IoT indication that nobody is home and will allow information to be collected thus invite a burglar. These challenges Ubiquitous information from nearby physical sensors and Web will become more pressing as use of the Users often need help when they en- services and then shared between de- Physical Web continues to grow. counter an unfamiliar device. Tra- vices on a scale that has not been pos- ditional products were sold with a sible before. As a result, the Physical user manual—later, they might have Web will lower uncertainty and im- erging the virtual Web with included an informational CD. More prove accuracy. A consequence is that the IoT will enable really recently, a customer support URL is future “smart devices” will become Msmart devices, providing provided that points to online doc- much smarter. smarter automation and services. As- uments, and even in the event that sociating a Web URI with every person, this is lost, a simple Web search for Actions and control place, or thing forms the basic mecha- the model number will usually locate As a complement to sensing, the IoT nism for bridging these two technol- the online manual. In the IoT future, ofers us a way to control the physical ogies. A key enabler is the ability to this problem can be solved by the world through displays, actuators, discover proximate objects, and BLE Physical Web enabling all products and switches. Many modern systems beacons containing URIs are a useful to transmit a wireless machine-read- beneft from remote control because it tool. Web browsers can readily display able URL that can be received by a simplifes physical interaction design Web information along with descrip- nearby smartphone or tablet with lit- and extends capabilities. In the Phys- tions of nearby IoT objects; they are a tle effort from the user. ical Web paradigm, anything with promising familiar on-ramp to the IoT.

34 COMPUTER WWW.COMPUTER.ORG/COMPUTER______

ABOUT THE AUTHORS

ROY WANT is a research scientist at Google. His research interests include mobile and ubiquitous computing. Want received a PhD in computer science from

Cambridge University. He is an ACM and IEEE Fellow. Contact him at ______roywant@ gmail.com______or via www.roywant.com/cs.

There is a reason people are excited BILL N. SCHILIT is a research scientist at Google. His research focuses on about the IoT: it feels like a big oppor- smart personal and mobile technologies supporting knowledge work. Schilit tunity to improve how we design and received a PhD in computer science from Columbia University. He is an IEEE build products. Making the IoT as ac- Fellow, a member of the IEEE Computer Society and ACM, and associate EIC of

cessible and useful as the Web is likely Computer. Contact him at [email protected]. an even bigger opportunity. SCOTT JENSON is a user experience strategist at Google. He has been in the REFERENCES design business for over 30 years, working on projects such as Mac System 7, 1. M. Satyanarayanan, “Pervasive Apple’s User Interface Guidelines, the Newton, Google Mobile Maps, and now Computing: Vision and Challenges,” the Physical Web. Contact him at [email protected]. IEEE Personal Comm., vol. 8, no. 4, 2001, pp. 10–17. 2. M. Weiser, “The Computer for the 21st Century,” Scientifc Am., vol. 265, no. 3, Sept 1991; www.scientifc 11. C. Anderson, “The Long Tail,” Wired, Selected CS articles and american.com/article/the-computer vol. 12, no. 10, 2004; http://archive columns are also available for ______-for-the-21st-century/. .wired.com/wired/archive/12.10/tail free at http://ComputingNow. . 3. T. Kindberg et al., “People Places and ____.html. computer.org Things: Web Presence for the Real World,” ACM J. Mobile Networks and Applications, vol. 7, no. 5, 2002, pp. 365–376. 4. R. Want et al., “Bridging the Physical and Virtual Worlds with Electronic Tags,” Proc. ACM SIGCHI, 1999, pp. 370–377. On Computing 5. S. Jain et al., “Exploiting Mobility for Energy Efcient Data Collection in podcast Wireless Sensor Networks,” Mobile www.computer.org/oncomputing Networks and Applications, vol. 11, no. 3, 2006, pp. 327–339. 6. R. Want, “RFID: The Key to Automat- ing Everything,” Scientifc Am., Jan. 2004, pp. 56–65. 7. H. Kato and K.T. Tan, “Pervasive 2D Barcodes for Camera Phone Applica- tions,” IEEE Pervasive Computing, vol. 6, no. 4, 2007, pp. 76–85. 8. R. Heydon, Bluetooth Low Energy, Prentice Hall, 2013. 9. B.N. Schilit and U. Sengupta, “Device Ensembles,” Computer, vol. 37, no. 12, 2004, pp. 56–64. 10. M. Satyanarayanan et al., “The Case for VM-Based Cloudlets in Mobile Computing,” IEEE Pervasive Comput- ing, vol. 8, no. 4, 2009, pp. 14–23.

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