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|Victoria Charles||Parkstone International|
|James Governor||Adobe Developer Library||ePub|
Everything deep is also simple and can be reproduced simply as long as its reference to the whole truth is maintained. But what matters is not what is witty but what is true.
Its time to move from Web 2.0 models to a Web 2.0 Reference Architecture, exploring more technical aspects that developers and architects must consider when building applications. In the process, well map the model in Chapter4 to a technology view that facilitates the new patterns of interaction that we cover in Chapter7.
This Web 2.0 Reference Architecture does not reflect any constraints regarding implementation; its merely an artifact that developers, architects, and entrepreneurs can use to help them design and build Web 2.0 applications. For software architects and developers, a layered reference architecture serves to align their technical views regarding various aspects. More importantly, it offers a good starting place for anyone wishing to develop applications based on the topic covered by the reference architecture (in this case, Web 2.0). As with the model in the previous chapter, you should view this reference architecture as a starting point for your technology road maps, not the one true normative architecture for Web 2.0 application development.See All Chapters
|Matthew MacDonald||O'Reilly Media||ePub|
Getting text into a Web page is easy. All you need to do is open an HTML file, drop in your content, and add the occasional formatting tag. Unfortunately, getting text to look exactly the way you want is a completely different story.
One of the first things you’ll notice when you start working on a site is how little control HTML gives you. When you create a Web page, you’re at the mercy of your viewers’ Web browsers, their bizarre preference settings, and a dozen other details beyond your control. Under these conditions, writing a perfect page feels like trying to compose a 90-minute symphony with a triangle and a pair of castanets.
Faced with these limitations, what’s an enterprising Web developer to do? The first step is to learn the basic tags you can use to structure your text by marking up paragraphs, sections, and lists. That’s the task you’ll tackle in this chapter. The second step—which you won’t dive into until the next chapter—is to apply style sheets, a powerful page formatting technology that lets you unleash your markup skills across multiple pages or even your entire site.See All Chapters
|Bill Wilder||O'Reilly Media||ePub|
This pattern focuses on applying the MapReduce data processing pattern.
MapReduce in this chapter is explicitly tied to the use of Hadoop since that helps pin down its capabilities and avoid confusion with other variants. The term MapReduce is used except when directly referencing the Hadoop project (which is introduced below).
MapReduce is a data processing approach that presents a simple programming model for processing highly parallelizable data sets. It is implemented as a cluster, with many nodes working in parallel on different parts of the data. There is large overhead in starting a MapReduce job, but once begun, the job can be completed rapidly (relative to conventional approaches).
MapReduce requires writing two functions: a mapper and a reducer. These functions accept data as input and then return transformed data as output. The functions are called repeatedly, with subsets of the data, with the output of the mapper being aggregated and then sent to the reducer. These two phases sift through large volumes of data a little bit at a time.See All Chapters
|Gerald Carter||O'Reilly Media||ePub|
I have a fairly good memory for numbers, phone numbers in particular. This fact amazes my wife. For those numbers I cannot recall to the exact digit, I have a dozen or so slots in my cell phone. However, as the company I worked for grew, so did the list of people with whom I needed to stay in contact. And I didn't just need phone numbers; I needed email and postal addresses as well. My cell phone's limited capabilities were no longer adequate for maintaining the necessary information.
So I eventually broke down and purchased a PDA. I was then able to store contact information for thousands of people. Still, two or three times a day I found myself searching the company's contact database for someone's number or address. And I still had to go to other databases (phone books, corporate client lists, and so on) when I needed to look up someone who worked for a different company.
Computer systems have exactly the same problem as humansboth require the capability to locate certain types of information easily, efficiently, and quickly. During the early days of the ARPAnet, a listing of the small community of hosts could be maintained by a central authoritySRI's Network Information Center (NIC). As TCP/IP became more widespread and more hosts were added to the ARPAnet, maintaining a centralized list of hosts became a pipe dream. New hosts were added to the network before everyone had even received the last, now outdated, copy of the famous HOSTS.TXT file. The only solution was to distribute the management of the host namespace. Thus began the Domain Name System (DNS), one of the most successful directory services ever implemented on the Internet.See All Chapters
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