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What​ is big data and how do I learn about it?Big Data is defined by the three V’s:Volume—large amounts of data;Variety—the data comes in different forms, including traditional databases, images, documents, and complex records;Velocity—the content of the data is constantly changing through the absorption of complementary data collections, the introduction of previously archived data or legacy collections, and from streamed data arriving from multiple sources.It is important to distinguish Big Data from “lots of data” or “massive data.” In a Big Data Resource, all three V’s must apply. It is the size, complexity, and restlessness of Big Data resources that account for the methods by which these resources are designed, operated, and analyzed.The term “lots of data” is often applied to enormous collections of simple-format records. For example every observed star, its magnitude and its location; the name and cell phone number of every person living in the United States; and the contents of the Web.These very large datasets are sometimes just glorified lists. Some “lots of data” collections are spreadsheets (2-dimensional tables of columns and rows), so large that we may never see where they end.Big Data resources are not equivalent to large spreadsheets, and a Big Data resource is never analyzed in its totality. Big Data analysis is a multi-step process whereby data is extracted, filtered, and transformed, with analysis often proceeding in a piecemeal, sometimes recursive, fashion. As you read this book, you will find that the gulf between “lots of data” and Big Data is profound; the two subjects can seldom be discussed productively within the same venue.Big Data Versus Small DataActually, the main function of Big Science is to generate massive amounts of reliable and easily accessible data... Insight, understanding, and scientific progress are generally achieved by ‘small science.’Big Data is not small data that has become bloated to the point that it can no longer fit on a spreadsheet, nor is it a database that happens to be very large. Nonetheless, some professionals who customarily work with relatively small data sets, harbor the false impression that they can apply their spreadsheet and database know-how directly to Big Data resources without attaining new skills or adjusting to new analytic paradigms.As they see things, when the data gets bigger, only the computer must adjust (by getting faster, acquiring more volatile memory, and increasing its storage capabilities); Big Data poses no special problems that a supercomputer could not solve. More information please refer to the Office 2019 Guide.This attitude, which seems to be prevalent among database managers, programmers, and statisticians, is highly counterproductive. It will lead to slow and ineffective software, huge investment losses, bad analyses, and the production of useless and irreversibly defective Big Data resources.Let us look at a few of the general differences that can help distinguish Big Data and small data. – Goals small data—Usually designed to answer a specific question or serve a particular goal. Big Data—Usually designed with a goal in mind, but the goal is flexible and the questions posed are protean.Here is a short, imaginary funding announcement for Big Data grants designed “to combine high-quality data from fisheries, coast guard, commercial shipping, and coastal management agencies for a growing data collection that can be used to support a variety of governmental and commercial management studies in the Lower Peninsula.”In this fictitious case, there is a vague goal, but it is obvious that there really is no way to completely specify what the Big Data resource will contain, how the various types of data held in the resource will be organized, connected to other data resources, or usefully analyzed. Nobody can specify, with any degree of confidence, the ultimate destiny of any Big Data project; it usually comes as a surprise.– Locationsmall data—Typically, contained within one institution, often on one computer, sometimes in one file.Big Data—Spread throughout electronic space and typically parceled onto multiple Internet servers, located anywhere on earth.– Data structure and content small data—Ordinarily contains highly structured data. The data domain is restricted to a single discipline or sub-discipline. The data often comes in the form of uniform records in an ordered spreadsheet.PRINCIPLES AND PRACTICE OF BIG DATABig Data—Must be capable of absorbing unstructured data (e.g., such as free-text documents, images, motion pictures, sound recordings, physical objects). The subject matter of the resource may cross multiple disciplines, and the individual data objects in the resource may link to data contained in other, seemingly unrelated, Big Data resources.– Data preparationsmall data—In many cases, the data user prepares her own data, for her own purposes. Big Data—The data comes from many diverse sources, and it is prepared by many people. The people who use the data are seldom the people who have prepared the data.– Longevitysmall data—When the data project ends, the data is kept for a limited time (seldom longer than 7 years, the traditional academic life-span for research data); and then discarded.Big Data—Big Data projects typically contain data that must be stored in perpetuity. Ideally, the data stored in a Big Data resource will be absorbed into other data resources. Many Big Data projects extend into the future and the past (e.g., legacy data), accruing data prospectively and retrospectively.– Measurementssmall data—Typically, the data is measured using one experimental protocol, and the data can be represented using one set of standard units.Big Data—Many different types of data are delivered in many different electronic formats. Measurements, when present, may be obtained by many different protocols. Verifying the quality of Big Data is one of the most difficult tasks for data managers. [Glossary Data Quality Act]– Reproducibilitysmall data—Projects are typically reproducible. If there is some question about the quality of the data, the reproducibility of the data, or the validity of the conclusions drawn from the data, the entire project can be repeated, yielding a new data set.Big Data—Replication of a Big Data project is seldom feasible. In general, the most that anyone can hope for is that bad data in a Big Data resource will be found and flagged as such.– Stakessmall data—Project costs are limited. Laboratories and institutions can usually recover from the occasional small data failure.Big Data—Big Data projects can be obscenely expensive. A failed Big Data effort can lead to bankruptcy, institutional collapse, mass firings, and the sudden disintegration of all the data held in the resource. As an example, a United States National Institutes of Health Big Data project known as the “NCI cancer biomedical informatics grid” cost at least $350 million for fiscal years 2004–10.An ad hoc committee reviewing the resource found that despite the intense efforts of hundreds of cancer researchers and information specialists, it had accomplished so little and at so great an expense that a project moratorium was called.Soon thereafter, the resource was terminated. Though the costs of failure can be high, in terms of money, time, and labor, Big Data failures may have some redeeming value. Each failed effort lives on as intellectual remnants consumed by the next Big Data effort.– Introspectionsmall data—Individual data points are identified by their row and column location within a spreadsheet or database table. If you know the row and column headers, you can find and specify all of the data points contained within.Big Data—Unless the Big Data resource is exceptionally well designed, the contents and organization of the resource can be inscrutable, even to the data managers. Complete access to data, information about the data values, and information about the organization of the data are achieved through a technique herein referred to as introspection.– Analysissmall data—In most instances, all of the data contained in the data project can be analyzed together, and all at once.Big Data—With few exceptions, such as those conducted on supercomputers or in parallel on multiple computers, Big Data is ordinarily analyzed in incremental steps. The data are extracted, reviewed, reduced, normalized, transformed, visualized, interpreted, and re-analyzed using a collection of specialized methods.Whence Comest Big Data?Often, the impetus for Big Data is entirely ad hoc. Companies and agencies are forced to store and retrieve huge amounts of collected data (whether they want to or not). Generally, Big Data comes into existence through any of several different mechanisms:– An entity has collected a lot of data in the course of its normal activities and seeks to organize the data so that materials can be retrieved, as needed.The Big Data effort is intended to streamline the regular activities of the entity. In this case, the data is just waiting to be used. The entity is not looking to discover anything or to do anything new. It simply wants to use the data to accomplish what it has always been doing;only better. The typical medical center is a good example of an “accidental” Big Data resource. The day-to-day activities of caring for patients and recording data into hospital information systems results in terabytes of collected data, in forms such as laboratory reports, pharmacy orders, clinical encounters, and billing data.Most of this information is generated for one-time specific use (e.g., supporting a clinical decision, collecting payments for a procedure). It occurs to the administrative staff that the collected data can be used, in its totality, to achieve mandated goals: improving the quality of service, increasing staff efficiency, and reducing operational costs.– An entity has collected a lot of data in the course of its normal activities and decides that there are many new activities that could be supported by their data.Consider modern corporations; these entities do not restrict themselves to one manufacturing process or one target audience. They are constantly looking for new opportunities.Their collected data may enable them to develop new products based on the preferences of their loyal customers, to signNow new markets, or to market and distribute items via the Web. These entities will become hybrid Big Data/manufacturing enterprises.– An entity plans a business model based on a Big Data resource.Unlike the previous examples, this entity starts with Big Data and adds a physical component secondarily. Amazon and FedEx may fall into this category, as they began with a plan for providing a data-intense service (e.g., the Amazon Web catalog and the FedEx package tracking system).The traditional tasks of warehousing, inventory, pick-up, and delivery had been available all along but lacked the novelty and efficiency afforded by Big Data.– An entity is part of a group of entities that have large data resources, all of whom understand that it would be to their mutual advantage to federate their data resources.An example of a federated Big Data resource would be hospital databases that share electronic medical health records.– An entity with skills and vision develops a project wherein large amounts of data are collected and organized, to the benefit of themselves and their user-clients.An example would be a massive online library service, such as the U.S. National Library of Medicine’s PubMed catalog, or the Google Books collection.– An entity has no data and has no particular expertise in Big Data technologies, but it has money and vision.The entity seeks to fund and coordinate a group of data creators and data holders, who will build a Big Data resource that can be used by others. Government agencies have been the major benefactors. These Big Data projects are justified if they lead to important discoveries that could not be attained at a lesser cost with smaller data resources.The Most Common Purpose of Big Data Is to Produce Small DataIf I had known what it would be like to have it all, I might have been willing to settle for less.Imagine using a restaurant locater on your smartphone. With a few taps, it lists the Italian restaurants located within a 10-block radius of your current location.The database being queried is big and complex (a map database, a collection of all the restaurants in the world, their longitudes and latitudes, their street addresses, and a set of ratings provided by patrons, updated continuously), but the data that it yields is small (e.g., five restaurants, marked on a street map, with pop-ups indicating their exact address, telephone number, and ratings). Your task comes down to selecting one restaurant from among the five, and dining thereat.In this example, your data selection was drawn from a large data set, but your ultimate analysis was confined to a small data set (i.e., five restaurants meeting your search criteria). The purpose of the Big Data resource was to proffer the small data set. No analytic work was performed on the Big Data resource; just search and retrieval.The real labor of the Big Data resource involved collecting and organizing complex data so that the resource would be ready for your query. Along the way, the data creators had many decisions to make (e.g., Should bars be counted as restaurants? What about takeaway only shops? What data should be collected? How should missing data be handled? How will data be kept current?Big Data is seldom if ever, analyzed in toto. There is almost always a drastic filtering process that reduces Big Data into smaller data. This rule applies to scientific analyses. The Australian Square Kilometre Array of radio telescopes [8], WorldWide Telescope, CERN’s Large Hadron Collider and the Pan-STARRS (Panoramic Survey Telescope and Rapid Response System) array of telescopes produce petabytes of data every day. Researchers use these raw data sources to produce much smaller data sets for analysis [9].Here is an example showing how workable subsets of data are prepared from Big Data resources. Blazars are rare super-massive black holes that release jets of energy that move at near-light speeds. Cosmologists want to know as much as they can about these strange objects. A first step to studying blazars is to locate as many of these objects as possible.Afterward, various measurements on all of the collected blazars can be compared, and their general characteristics can be determined. Blazars seem to have a gamma ray signature that is not present in other celestial objects. The WISE survey collected infrared data on the entire observable universe.Researchers extracted from the Wise data every celestial body associated with an infrared signature in the gamma-ray range that was suggestive of blazars; about 300 objects. Further research on these 300 objects led the researchers to believe that about half were blazars [10]. This is how Big Data research often works; by constructing small data sets that can be productively analyzed.Because a common role of Big Data is to produce small data, a question that data managers must ask themselves is: “Have I prepared my Big Data resource in a manner that helps it become a useful source of small data?”Big Data Sits at the Center of the Research UniverseIn the past, scientists followed a well-trodden path toward truth: hypothesis, then experiment, then data, then analysis, then publication. The manner in which a scientist analyzed his or her data was crucial because other scientists would not have access to the same data and could not re-analyze the data for themselves.Basically, the results and conclusions described in the manuscript was the scientific product. The primary data upon which the results and conclusion were based (other than one or two summarizing tables) were not made available for review. Scientific knowledge was built on trust. Customarily, the data would be held for 7 years, and then discarded.In the Big data paradigm, the concept of a final manuscript has little meaning. Big Data resources are permanent, and the data within the resource is immutable. Any scientist’s analysis of the data does not need to be the final word; another scientist can access and re-analyze the same data over and over again.Original conclusions can be validated or discredited. New conclusions can be developed. The centerpiece of science has moved from the manuscript, whose conclusions are tentative until validated, to the Big Data resource, whose data will be tapped repeatedly to validate old manuscripts and spawn new manuscripts.Today, hundreds or thousands of individuals might contribute to a Big Data resource. The data in the resource might inspire dozens of major scientific projects, hundreds of manuscripts, thousands of analytic efforts, and millions or billions of search and retrieval operations. The Big Data resource has become the central, massive object around which universities, research laboratories, corporations, and federal agencies orbit.These orbiting objects draw information from the Big Data resource, and they use the information to support analytic studies and to publish manuscripts. Because Big Data resources are permanent, any analysis can be critically examined using the same set of data, or re-analyzed anytime in the future. Because Big Data resources are constantly growing forward in time (i.e., accruing new information) and backward in time (i.e., absorbing legacy data sets), the value of the data is constantly increasing.Big Data resources are the stars of the modern information universe. All matter in the physical universe comes from heavy elements created inside stars, from lighter elements.All data in the informational universe is complex data built from simple data. Just as stars can exhaust themselves, explode, or even collapse under their own weight to become black holes; Big Data resources can lose funding and die, release their contents and burst into nothingness, or collapse under their own weight, sucking everything around them into a dark void. It is an interesting metaphor.GlossaryBig Data resource A Big Data collection that is accessible for analysis. Readers should understand that there are collections of Big Data (i.e., data sources that are large, complex, and actively growing) that are not designed to support analysis; hence, not Big Data resources.Such Big Data collections might include some of the older hospital information systems, which were designed to deliver individual patient records upon request; but could not support projects wherein all of the data contained in all of the records were opened for selection and analysis. Aside from privacy and security issues, opening a hospital information system to these kinds of analyses would place enormous computational stress on the systems (i.e., produce system crashes).In the late 1990s and the early 2000s, data warehousing was popular. Large organizations would collect all of the digital information created within their institutions, and these data were stored as Big Data collections, called data warehouses. If an authorized person within the institution needed some specific set of information (e.g., emails sent or received in February 2003; all of the bills paid in November 1999), it could be found somewhere within the warehouse.For the most part, these data warehouses were not true Big Data resources because they were not organized to support a full analysis of all of the contained data. Another type of Big Data collection that may or may not be considered a Big Data resource are compilations of scientific data that are accessible for analysis by private concerns, but closed for analysis by the public.In this case, a scientist may make a discovery based on her analysis of a private Big Data collection, but the research data is not open for critical review. In the opinion of some scientists, including myself, if the results of data analysis are not available for review, then the analysis is illegitimate. Of course, this opinion is not universally shared, and Big Data professionals hold various definitions for a Big Data resource.ConclusionsConclusions are the interpretations made by studying the results of an experiment or a set of observations. The term “results” should never be used interchangeably with the term “conclusions.” Remember, results are verified. Conclusions are validated.Data Quality Act In the United States the data upon which public policy is based must have quality and must be available for review by the public. Simply put, public policy must be based on verifiable data. The Data Quality Act of 2002 requires the Office of Management and Budget to develop government-wide standards for data quality.Data manager This book uses “data manager” as a catchall term, without attaching any specific meaning to the name. Depending on the institutional and cultural milieu, synonyms and plesionyms (i.e., near-synonyms) for data manager would include technical lead, team liaison, data quality manager, chief curator, chief of operations, project manager, group supervisor, and so on.Data resource A collection of data made available for data retrieval. The data can be distributed over servers located anywhere on earth or in space. The resource can be static (i.e., having a fixed set of data), or in flux. Pseudonyms for data resource is a data warehouse, data repository, data archive, and data store.Database A software application designed specifically to create and retrieve large numbers of data records (e.g., millions or billions). The data records of a database are persistent, meaning that the application can be turned off, then on, and all the collected data will be available to the user.Grid A collection of computers and computer resources (typically networked servers) that are coordinated to provide the desired functionality. In the most advanced Grid computing architecture, requests can be broken into computational tasks that are processed in parallel on multiple computers and transparently (from the client’s perspective) assembled and returned. The Grid is the intellectual predecessor of Cloud computing. Cloud computing is less physically and administratively restricted than Grid computing.ImmutabilityImmutability is the principle that data collected in a Big Data resource is permanent and can never be modified. At first thought, it would seem that immutability is a ridiculous and impossible constraint. In the real world, mistakes are made, information changes, and the methods for describing information changes. This is all true, but the astute Big Data manager knows how to accrue informa-tion into data objects without changing the pre-existing data.IntrospectionWell-designed Big Data resources support introspection, a method whereby data objects within the resource can be interrogated to yield their properties, values, and class membership. Through introspection, the relationships among the data objects in the Big Data resource can be examined and the structure of the resource can be determined. Introspection is the method by which a data user can find everything there is to know about a Big Data resource without downloading the complete resource.Large Hadron Collider The Large Hadron Collider is the world’s largest and most powerful particle accelerator and is expected to produce about 15 petabytes (15 million gigabytes) of data annually.Legacy data Data collected by an information system that has been replaced by a newer system, and which cannot be immediately integrated into the newer system’s database. For example, hospitals regularly replace their hospital information systems with new systems that promise greater efficiencies, expanded services, or improved interoperability with other information systems. In many cases, the new system cannot readily integrate the data collected from the older system.The previously collected data becomes a legacy to the new system. In such cases, legacy data is simply “stored” for some arbitrary period of time in case someone actually needs to retrieve any of the legacy data.After a decade or so the hospital may find itself without any staff members who are capable of locating the storage site of the legacy data, or moving the data into a modern operating system, or interpreting the stored data, or retrieving appropriate data records, or producing a usable query output.MapReduceA method by which computationally intensive problems can be processed on multiple computers, in parallel. The method can be divided into a mapping step and a reducing step.In the mapping step, a master computer divides a problem into smaller problems that are distributed to other computers. In the reducing step, the master computer collects the output from the other computers. Although MapReduce is intended for Big Data resources and can hold petabytes of data, most Big Data problems do not require MapReduce.Missing data Most complex data sets have missing data values. Somewhere along the line data elements were not entered, records were lost, or some systemic error produced empty data fields. Big Data, being large, complex, and composed of data objects collected from diverse sources, is almost certain to have missing data.Various mathematical approaches to missing data have been developed; commonly involving assigning values on a statistical basis; so-called imputation methods. The underlying assumption for such methods is that missing data arise at random. When missing data arises non-randomly, there is no satisfactory statistical fix.The Big Data curator must track down the source of the errors and somehow rectify the situation. In either case, the issue of missing data introduces a potential bias and it is crucial to fully document the method by which missing data is handled. In the realm of clinical trials, only a minority of data analyses bothers to describe their chosen method for handling missing data.MutabilityMutability refers to the ability to alter the data held in a data object or to change the identity of a data object. Serious Big Data is not mutable. Data can be added, but data cannot be erased or altered. Big Data resources that are mutable cannot establish a sensible data identification system, and cannot support verification and validation activities.The legitimate ways in which we can record the changes that occur in unique data objects (e.g., humans) over time, without ever changing the key/value data attached to the unique object.For programmers, it is important to distinguish data mutability from object mutability, as it applies in Python and other object-oriented programming languages. Python has two immutable objects: strings and tuples.Intuitively, we would probably guess that the contents of a string object cannot be changed, and the contents of a tuple object cannot be changed. This is not the case. Immutability, for programmers, means that there are no methods available to the object by which the contents of the object can be altered.Specifically, a Python tuple object would have no methods it could call to change its own contents. However, a tuple may contain a list, and lists are mutable. For example, a list may have an append method that will add an item to the list object. You can change the contents of a list contained in a tuple object without violating the tuple’s immutability.Parallel computing Some computational tasks can be broken down and distributed to other computers, to be calculated “in parallel.” The method of parallel programming allows a collection of desktop computers to complete intensive calculations of the sort that would ordinarily require the aid of a super-computer.Parallel programming has been studied as a practical way to deal with the higher computational demands brought by Big Data. Although there are many important problems that require parallel computing, the vast majority of Big Data analyses can be easily accomplished with a single, off-the-shelf personal computer.Protocol A set of instructions, policies, or fully described procedures for accomplishing a service, operation, or task. Protocols are fundamental to Big Data. Data is generated and collected according to protocols. There are protocols for conducting experiments, and there are protocols for measuring the results.There are protocols for choosing the human subjects included in a clinical trial, and there are protocols for interacting with the human subjects during the course of the trial. All network communications are conducted via protocols; the Internet operates under a protocol (TCP-IP, Transmission Control Protocol-Internet Protocol).Query The term “query” usually refers to a request, sent to a database, for information (e.g., Web pages, documents, lines of text, images) that matches a provided word or phrase (i.e., the query term). More generally a query is a parameter or set of parameters that are submitted as input to a computer program that searches a data collection for items that match or bear some relationship to the query parameters.In the context of Big Data, the user may need to find classes of objects that have properties relevant to a particular area of interest. In this case, the query is basically introspective, and the output may yield metadata describing individual objects, classes of objects, or the relationships among objects that share particular properties.For example, “weight” may be a property, and this property may fall into the domain of several different classes of data objects. The user might want to know the names of the classes of objects that have the “weight” property and the numbers of object instances in each class.Eventually, the user might want to select several of these classes (e.g., including dogs and cats, but excluding microwave ovens) along with the data object instances whose weights fall within a specified range (e.g., 20–30 pound). This approach to querying could work with any data set that has been well specified with metadata, but it is particularly important when using Big Data resources.Raw data Raw data is the unprocessed, original data measurement, coming straight from the instrument to the database with no intervening interference or modification. In reality, scientists seldom, if ever, work with raw data.When an instrument registers the amount of fluorescence emitted by a hybridization spot on a gene array, or the concentration of sodium in the blood, or virtually any of the measurement that we receive as numeric quantities, the output is produced by an algorithm executed by the measurement instrument.Pre-processing of data is commonplace in the universe of Big Data, and data managers should not labor under the false impression that the data received is “raw,” simply because the data has not been modified by the person who submits the data.Results The term “results” is often confused with the term “conclusions.” Interchanging the two concepts is a source of confusion among data scientists. In the strictest sense, “results” consist of the full set of experimental data collected by measurements. In practice, “results” are provided as a small subset of data distilled from the raw, original data.In a typical journal article, selected data subsets are packaged as a chart or graph that emphasizes some point of interest. Hence, the term “results” may refer, erroneously, to subsets of the original data, or to visual graphics intended to summarize the original data. Conclusions are the inferences drawn from the results. Results are verified; conclusions are validated.Science, Of course, there are many different definitions of science, and inquisitive students should be encouraged to find a conceptualization of science that suits their own intellectual development. For me, science is all about finding general relationships among objects.In the so-called physical sciences the most important relationships are expressed as mathematical equations (e.g., the relationship between force, mass, and acceleration; the relationship between voltage, current, and resistance). In the so-called natural sciences, relationships are often expressed through classifications (e.g., the classification of living organisms).Scientific advancement is the discovery of new relationships or the discovery of a generalization that applies to objects hitherto confined within disparate scientific realms (e.g., evolutionary theory arising from observations of organisms and geologic strata). Engineering would be the area of science wherein scientific relationships are exploited to build new technology.Square Kilometer Array The Square Kilometer Array is designed to collect data from millions of connected radio telescopes and is expected to produce more than one exabyte (1 billion gigabytes) every day.