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Metcalfe's Law, Web 2.0, and the Semantic WebIn talking about the Web, whether the original model, the so-called "Web 2.0", or the emerging Semantic Web (aka Web 3.0), one of the most important things to keep in mind is the network effect. The power of the Web emerges through the link space realized between Web pages. This is evidenced in a number of pieces of work, most famously the PageRank algorithm (Brin and Page, 1998) that was behind the early success of Google. Unlike traditional information retrieval algorithms, which were solely based on the information content of the individual pages, PageRank takes into effect how Web pages are linked to each other. By coupling this information with traditional indexing schemes, the system was able to outperform its competitors.
The network effect describes the value of a service to a user that arises from the number of people using the service. At its core, it captures that value increases as the number of users increases, because the potential links increase for every user as a new person joins. This is best quantified by what has come to be known as Metcalfe's Law. This proposition developed by Bob Metcalfe in the early 1980s, was originally defined to better explain to his customers why they needed more Ethernet boards than they were buying. Metcalfe hypothesized that while the cost of the network grew linearly with the number of connections, the value was proportional to the square of the number of users. For example, given n users of ethernet cards, the numberWriting Applications Using PHPMany developers have learned to use PHP over the years because it’s a good solution for creating Web pages and the price is right. The PHP acronym is like many other new acronyms for the Internet—the acronym is recursive (refers back to itself). PHP stands for PHP Hypertext Processor. This general-purpose HTML scripting language works much like ASP (see Chapter 6) or other page description languages you might have used. Essentially, you mix HTML with scripting information. When the PHP process sees HTML, it sends the text directly to the user. It processes any scripting information, and passes the resulting HTML to the user as well.
This chapter helps you discover how PHP works with Amazon Web Services. I’m assuming that you already know something about PHP, but the first two sections provide some suggestions on how to learn more about PHP. Because PHP runs on so many platforms, you’ll also find some suggested resources for getting and installing PHP for your particular server. These instructions might require a little technical knowledge on your part, so make sure you understand what the instructions require before you perform them.
The examples in this chapter show how to use PHP to create an Amazon Web Services application. The first example provides simple instructions for accessing the Web service without any fancy application features. You’ll also find an application that shows how to use PHP with MySQL, an open source database. In fact, you can download every piece of software in this chapter free andMapping MashupsAs part of a large undergraduate history course he teaches about World War II, Dr. Martinez developed a mapping mashup that he introduces to the 150 students at the beginning of the semester. The mashup, which works with Google maps, represents major events leading up to and during the war. Fundamentally, it’s a map, he explains, showing them on a projection screen that it works very much like the online mapping tools students regularly use. The map covers virtually the entire globe, and users can move around the world, zooming in and out, showing the area of search as a map, satellite images, or satellite images with maps, dates, and events superimposed.
When students zoom in on Europe, they see flags scattered around the continent and into Asia. Similar maps dot Japan, Southeast Asia, and the South Pacific. When clicked, each flag opens a pop-up box that names the location, explains what happened there and when, and shows a photograph of that site at or close to the date in question. Flags correspond to important battles, political events, treaties that were signed, and cities such as Vichy, the wartime capital of France. The text in the box also includes links to articles that talk in depth about what took place in each location and the significance of that event. Students can zoom in to particular locations and see satellite images of what the place looks like today. They can also get an idea about the terrain where soldiers fought and died.
DuringCOM+ Design PatternsIn the last five years, design patterns have become extremely important in computer science. The reason they are important is that if you identify distinct common patterns, these patterns can then be re-used. Presented here is another design pattern that explains the evolution of most broad technologies like COM+.
The evolution design pattern is really a meta-pattern, a pattern about patterns. It describes how implementations are often aggregated into designs with a common framework. Once this common framework is established it is then possible to add new functionality across all the implementations. This can best be explained with a couple of pictures. Generally, implementations are originally designed in isolation. Each implementation is like an island
This may seem like a far-fetched example, but in reality, it closely emulates what happens in a software development project. Because each implementation is developed in isolation, it becomes next to impossible for a developer working on one implementation to help on any other implementations. As developers begin turning over (leaving the company for greener ($) pastures), new developers either within the same company or new hires, have a difficult time learning this extremely proprietary implementation. The implementation topples over.
To the rescue, comes the architect who points out that if the implementation used a common framework, then one developer could easily move from implementation to implementation without having to re-learn all from scratch. In this new paradigm, the implementations do not exist as islands, as they are no longer implemented in isolation. Now the implementations are dunesA Practical Dynamic Buffer Overflow DetectorDespite previous efforts in auditing software manually and automatically, buffer overruns are still being discovered in programs in use. A dynamic bounds checker detects buffer overruns in erroneous software before it occurs and thereby prevents attacks from corrupting the integrity of the system. Dynamic buffer overrun detectors have not been adopted widely because they either (1) cannot guard against all buffer overrun attacks (2) break existing code or (3) incur too high an overhead. This paper presents a practical detector called CRED (C Range Error Detector) that avoids each of these defeciencies.
CRED finds all buffer overrun attacks as it directly checks for the bounds of memory accesses. Unlike the original referent-object based bound-checking technique, CRED does not break existing cde because it uses a novel solution to support program manipulation of out-of-bounds addresses. Finally, by restricting the bounds checks to strings in a program, CRED’s overhead is greatly reduced without sacrificing protection in the experiments we performed.
Download A Practical Dynamic Buffer Overflow DetectorVerifying Web Services Security ConfigurationsXML Web Services provide a flexible API for building distributed systems as a collection of endpoints that can send and receive SOAP messages. These systems are secured using message-based cryptographic mechanisms defined in a series of specifications developed by Microsoft, IBM, and others. Such home-grown security protocols often go wrong; they are prone to a well-known class of attacks, formalized by Dolev and Yao, where an attacker can intercept, modify, and replay messages. The vulnerability is only increased by the flexible message formats and complex trust configurations allowed by the standards. Our goal is to verify the security of families of protocol configurations, such as those deployed for Microsoft’s WSE and Indigo web services implementations.
We propose a new specification language for writing machine-checkable descriptions of SOAP-based security protocol configurations and their properties. Our TulaFale language is based on the pi calculus (for writing collections of SOAP processors running in parallel), plus XML syntax (to express SOAP messaging), logical predicates (to construct and filter SOAP messages), and correspondence assertions (to specify authentication goals of protocols). Our implementation compiles TulaFale into the applied pi calculus, and then runs Blanchet’s resolution-based protocol verifier. The TulaFale implementation is available for download.
We also describe a high-level link language for describing security configurations, and demonstrate a tool that can automatically generate and analyze executable security policy deployments for web services written using WSE. This is the first tool we know of that can automatically analyze cryptographic configurations to find real errors and demonstrable attacks.
Download pdf VerifyingThe 12-in. PowerBook Thin and (Feature) Rich ReviewJust 4.6 pounds light enough to carry most anywhere, yet hefty enough to convey a feeling of solid construction. I believe it was Walt Mossberg at The Wall Street Journal who best summed up the 12-in. PowerBook. It s like one of those all-metal Leica cameras that just reeks of quality. I have to admit having taken a roller-coaster ride of sorts in the past couple of years since Ap p l e i n t roduced its aluminum PowerBooks. I fell fir s t for the 17-in. model (such widescreen real estate), then swooned for the first-generation 12-in. model (a hot little number in more ways than one, espe-cially when you sat it in your lap), then decided that for most users the midrange 15-in. model is the perfect blend of portability and power.
Along the way, I ve bought, borrowed or used just about eve ry combo of PowerBook features that Apple has built, and while I seem to have fin a l l y settled on the 17-in. model for my own use (I have one of the newer 1.67-GHz G4 PowerBooks at home), the entry - s i ze model is no slouch. T he old adage that you can never be too thin or too rich seems like a tailor-made description of what road warriors want in their laptops: thin, lightweight machines that are feature-rich and, of course, inexpensive. With its latest generation of Powe r B o o k s , u n veiled backGuide to Setting Up a Wireless NetworkThis guide has been commissioned by the Department for Education and Skills, in partnership with NIACE (National Institute of Adult and Continuing Education), to support those working with wireless networks for Adult and Community Learning. It has been written by the DirectSupport initiative, which has been supporting UK online centres, Wireless Outreach Projects, and similar Community ICT access programmes, since 2000. DirectSupport is run by the charity ruralnet|uk, together with other community development partners.
The guide is for learning practitioners, and their support staff, who are considering the installation of a new wireless network or want to understand the implications in extending an existing network by using wireless components. It offers information to tutors and community development practioners, who may work in outreach venues, in learning access centres, or in small organisations.
Those who may not have a technical team on call, and require simple DIY guidance on how to set up a small network of computers to share files, printers and connect to an existing Internet connection, will find this guide helpful.
It sets out to explain the basic principles behind wireless networking, the different standards available and the components needed to set up the network. It also discusses how to add a wireless segment to an existing network constructed using cables or wires – a wired network. It covers configuring the network, setting up network security and basic troubleshooting. The guide assumes a basic understanding of computer networking, but is not intended as a comprehensive guide to network design, management or10 Tips to Consider When Hiring an SEO VendorIt can be quite difficult to select a Search Engine Optimization (SEO) Vendor. One of the main reasons is because each vendor has different service offerings and quite often it’s like comparing apples with oranges. This White Paper will offer you tips on some crucial aspects of Search Engine Optimization and helps understand how you can compare services of different vendors. After reading this White Paper you can ask the right questions to SEO vendors and their answers will help you select a vendor who matches your needs.
Section I: How to shortlist SEO companies.
Use Google, Yahoo and MSN to search for SEO companies using keywords like Search Engine Optimization, SEO Companies, SEO services, Search Engine Optimization Services etc. Do not restrict yourself to just organic rankings, but look at paid listings also. There is a popular misconception that all good SEO vendors will rank on the first page of Google. Many SEO companies get credit links from the bottom of their client’s web site which can get them on the first page of Google. But they might not be able to use the same strategy for your web site. So it’s not necessarily true that only companies ranking naturally on Google’s first page are good. It might take you some time getting used to this concept, but once you consider this, it will open up your mind to a lot of potentially good vendors. You should ideally shortlist 3 to 5 vendors (by looking at the information available onIBM ThinkPad 390X Computer User Guide PdfWe at IBM have developed this ThinkPad computer to meet both your technical requirements and your high expec- tations. To help us continue to build products that address your mobile computing needs, please take a moment to complete the ThinkPad Registration. Identifying the Hardware Features Front View of the Computer (1) The LCD latches release the LCD when pressed and allow it to be opened. (2) The color LCD screen displays computer output. (3) The built-in microphone captures sound and voice when it is used with an application program capable of handling audio.
Note: The built-in microphone is located at the top right corner of the LCD for 12.1-/14.1-inch LCD models, or at the left lower edge of the LCD for 15.0-inch models. (4) The brightness control adjusts the brightness of the display. (5) The left and right internal speakers generate stereo sound. Note: The internal speakers are located below the LCD for 12.1-/14.1-inch LCD models, or on the front ends of the computer for 15.0-inch LCD models.
Download IBM ThinkPad 390X Computer User Guide Pdf
