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Chapter 3 MESSY Mansoureh Rousta.

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1 Chapter 3 MESSY Mansoureh Rousta

Cost Inexactitude We never wanted consider them unavoidable and learn to live with them Going to big data from small

3 In a world of small data Reducing errors
Ensuring high quality was a natural and essential impulse Collected a little information so it must be as accurate ass possible Scientific try to make their measurement more and more precise. (celestial bodies or microscope) Analyzing only a limited number of data points means errors may get amplified

4 If one could measure a phenomenon, the implicit belief was, one could understand it.
Later, measurement was tied to the scientific method of observation and explanation: the ability to quantify, record, and present reproducible results.

5 By the nineteenth century France…
developed a system of precisely defined units of measurement to capture space, time, and more, and had begun to get other nations to adopt the same standards. It was the apex of the age of measurement Just half a century later, in the 1920s, the discoveries of quantum mechanics shattered forever the dream of comprehensive and perfect measurement.

6 However in many new situations that are cropping up today, allowing for imprecision—for messiness—may be a positive feature, not a shortcoming

7 you can also increase messiness by combining different types of information from different sources, which don’t always align perfectly. Messiness can also refer to the inconsistency of formatting, for which the data needs to be “cleaned” before being processed.

8 Suppose we need to measure the temperature in a vineyard
One temperature sensor a sensor for every one of the hundreds of vines Now suppose we increase the frequency of the sensor readings The information will be a bit less accurate, but its great volume makes it worthwhile to forgo strict exactitude.

9 in many cases it is more fruitful to tolerate error than it would be to work at preventing it
For instance, we can accept some messiness in return for scale As Forrester, a technology consultancy, puts it, “Sometimes two plus two can equal 3.9, and that is good enough.” Of course the data can’t be completely incorrect, but we’re willing to sacrifice a bit of accuracy in return for knowing the general trend.

10 Everyone knows how much processing power has increased over the years as predicted by Moore’s Law, which states that the number of transistors on a chip doubles roughly every two years. This continual improvement has made computers faster and memory more plentiful BUT…

11 Fewer of us know that the performance of the algorithms that drive many of our systems has also increased—in many areas more than the improvement of processors under Moore’s Law. Many of the gains to society from big data, however, happen not so much because of faster chips or better algorithms but because there is more data.

12 For example, chess algorithms have changed only slightly in the past few decades
the way computers learn how to parse words as we use them in everyday speech Around 2000, Microsoft researchers Michele Banko and Eric Brill were looking for a method to improve the grammar checker that is part of the company’s Word program

13 They weren’t sure whether it would be more useful to put their effort into
improving existing algorithms, finding new techniques, or adding more sophisticated features The results were astounding. As more data went in, the performance of all four types of algorithms improved dramatically. Simple algorithm 75% to 95% Large data algorithm 86% to 94%

14 “These results suggest that we may want to reconsider the tradeoff between spending time and money on algorithm development versus spending it on corpus development,” Banko and Brill wrote in one of their research papers on the topic.

15 language translation few years after Banko and Brill …
researchers at rival Google were thinking along similar lines—but at an even larger scale Instead of testing algorithms with a billion words, they used a trillion. Google did this not to develop a grammar checker but to crack an even more complex nut: language translation

16 So-called machine translation has been a vision of computer pioneers since the dawn of computing in the 1940s The idea took on a special urgency during the Cold War At first, computer scientists opted for a combination of grammatical rules and a bilingual dictionary An IBM computer translated sixty Russian phrases into English in 1954, using 250 word pairs in the computer’s vocabulary and six rules of grammar. The results were very promising

17 The director of the research program, Leon Dostert of Georgetown University, predicted that…
By 1966 a committee of machine-translation grandees had to admit failure The problem was harder than they had realized it would be In the late 1980s, researchers at IBM had a novel idea…

18 In the 1990s IBM’s Candide project used ten years’ worth of Canadian parliamentary transcripts published in French and English—about three million sentence pairs Suddenly, computer translation got a lot better Eventually IBM pulled the plug.

19 But less than a decade later, in 2006, Google got into translation, as part of its mission to “organize the world’s information and make it universally accessible and useful.” Instead of nicely translated pages of text in two languages, Google availed itself of a larger but also much messier dataset: the entire global Internet and more Its trillion-word corpus amounted to 95 billion English sentences, albeit of dubious quality

20 Despite the messiness of the input, Google’s service works the best
By mid-2012 its dataset covered more than 60 languages The reason Google’s translation system works well is not that it has a smarter algorithm. It works well because its creators, like Banko and Brill at Microsoft, fed in more data—and not just of high quality Google was able to use a dataset tens of thousands of times larger than IBM’s Candide because it accepted messiness

21 More trumps better Messiness is difficult to accept for the conventional sampling analysts, who for all their lives have focused on preventing and eradicating messiness They work hard to reduce error rates when collecting samples, and to test the samples for potential biases before announcing their results

22 They use multiple error-reducing strategies
Such strategies are costly to implement and they are hardly feasible for big data Moving into a world of big data will require us to change our thinking about the merits of exactitude we no longer need to worry so much about individual data points biasing the overall analysis

23 At BP’s Cherry Point Refinery in Blaine, Washington, wireless sensors are installed throughout the plant, forming an invisible mesh that produces vast amounts of data in real time. The environment of intense heat and electrical machinery might distort the readings, resulting in messy data. But the huge quantity of information generated from both wired and wireless sensors makes up for those hiccups

24 When the quantity of data is vastly larger and is of a new type, exactitude in some cases is no longer the goal It bears noting that messiness is not inherent to big data. Instead it is a function of the imperfection of the tools we use to measure, record, and analyze information. If the technology were to somehow become perfect, the problem of inexactitude would disappear

25 Messiness in action In many areas of technology and society, we are leaning in favor of more and messy over fewer and exact These hierarchical systems have always been imperfect, as everyone familiar with a library card catalogue

26 For example, in 2011 the photo-sharing site Flickr held more than six billion photos from more than 75 million users. Trying to label each photo according to preset categories would have been useless. Would there really have been one entitled “Cats that look like Hitler”? Instead, clean taxonomies are being replaced by mechanisms that are messier but also eminently more flexible and adaptable to a world that evolves and changes

27 When we upload photos to Flickr, we “tag” them
Many of the Web’s most popular sites flaunt their admiration for imprecision over the pretense of exactitude For example likes in face book or twitter

28 Traditional database engines required data to be highly structured and precise.
Data wasn’t simply stored; it was broken up into “records” that contained fields. Each field held information of a particular type and length. For example…

29 The most common language for accessing databases has long been SQL, or “structured query language.”
The very name evokes its rigidity. But the big shift in recent years has been toward something called noSQL, which doesn’t require a preset record structure to work. It accepts data of varying type and size and allows it to be searched successfully.

30 Processing big data entails an inevitable loss of information
Pat Helland, one of the world’s foremost authorities on database design “lossy” Processing big data entails an inevitable loss of information

31 Hadoop, an open-source rival to Google’s MapReduce system
Traditional database design promises to deliver consistent results across time. If you ask for your bank account balance, for example, you expect to receive the exact amount…. While traditional systems would have a delay until all updates are made Instead, accepting messiness is a kind of solution Hadoop, an open-source rival to Google’s MapReduce system

32 typical data analysis requires an operation called “extract, transfer, and load,” or ETL
Hadoop: data can’t be moved and must be analyzed where it is Hadoop’s output isn’t as precise as that of relational databases: it can’t be trusted to launch a spaceship or to certify bank-account details. But for many less critical tasks, where an ultra-precise answer isn’t needed, it does the trick far faster than the alternatives

33 web pages and videos, remain dark
In return for living with messiness, we get tremendously valuable services that would be impossible at their scope and scale with traditional methods and tools. For example ZestFinance for loan According to some estimates only 5 percent of all digital data is “structured”—that is, in a form that fits neatly into a traditional database. Without accepting messiness, the remaining 95 percent of unstructured data so web pages and videos, remain dark

34 Big data, with its emphasis on comprehensive datasets and messiness, helps us get closer to reality than did our dependence on small data and accuracy

35 big data may require us to change, to become more comfortable with disorder and uncertainty

36 as the next chapter will explain, finding associations in data and acting on them may often be good enough

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