Data

The term data refers to qualitative or quantitative attributes of a variable or set of variables. Data (plural of "datum") are typically the results of measurements and can be the basis of graphs, images, or observations of a set of variables. Data are often viewed as the lowest level of abstraction from which information and then knowledge are derived. Raw data refers to a collection of numbers, characters, images or other outputs from devices that collect information to convert physical quantities into symbols, that are unprocessed.

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Etymology

The word data (pronounced /ˈdeɪtə/ DAY-tə, /ˈdætə/ DA-tə, or /ˈdɑːtə/ DAH-tə) is the Latin plural of datum, neuter past participle of dare, "to give", hence "something given". In discussions of problems in geometry, mathematics, engineering, and so on, the terms givens and data are used interchangeably. Also, data is a representation of a fact, figure, and idea. Such usage is the origin of data as a concept in computer science: data are numbers, words, images, etc., accepted as they stand.

Usage in English

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In English, the word datum is still used in the general sense of "something given". In cartography, geography, nuclear magnetic resonance and technical drawing it is often used to refer to a single specific reference datum from which distances to all other data are measured. Any measurement or result is a datum, but data point is more common, albeit tautological. Both datums (see usage in datum article) and the originally Latin plural data are used as the plural of datum in English, but data is more commonly treated as a mass noun and used with a verb in the singular form especially in, day-to-day usage. For example, This is all the data from the experiment. This usage is inconsistent with the rules of Latin grammar and traditional English (These are all the data from the experiment). Even when a very small quantity of data is referred to (One number, for example) the phrase piece of data is often used, as opposed to datum.

Many style guides and international organizations, such as the IEEE Computer Society, allow usage of data as either a mass noun or plural based on author preference. Other professional organizations and style guides require that authors treat data as a plural noun. For example, the Air Force Flight Test Center specifically states that the word data is always plural, never singular.

Data is accepted and often treated as a singular mass noun in everyday educated usage. Some major newspapers such as The New York Times use it alternately in the singular or plural. In the New York Times the phrases "the survey data are still being analyzed" and "the first year for which data is available" have appeared on the same day. In scientific writing data is often treated as a plural, as in These data do not support the conclusions, but many people now think of data as a singular mass entity like information and use the singular in general usage. British usage now widely accepts treating data as singular in standard English. including everyday newspaper usage at least in non-scientific use. UK scientific publishing still prefers treating it as a plural. Some UK university style guides recommend using data for both singular and plural use and some recommend treating it only as a singular in connection with computers.

Meaning of data, information and knowledge

The terms information and knowledge are frequently used for overlapping concepts. The main difference is in the level of abstraction being considered. Data is the lowest level of abstraction, information is the next level, and finally, knowledge is the highest level among all three.[citation needed] Data on its own carries no meaning. In order for data to become information, it must be interpreted and take on a meaning. For example, the height of Mt. Everest is generally considered as "data", a book on Mt. Everest geological characteristics may be considered as "information", and a report containing practical information on the best way to reach Mt. Everest's peak may be considered as "knowledge".

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Information as a concept bears a diversity of meanings, from everyday usage to technical settings. Generally speaking, the concept of information is closely related to notions of constraint, communication, control, data, form, instruction, knowledge, meaning, mental stimulus, pattern, perception, and representation.

Beynon-Davies uses the concept of a sign to distinguish between data and information; data are symbols while information occurs when symbols are used to refer to something. 

It is people and computers who collect data and impose patterns on it. These patterns are seen as information which can be used to enhance knowledge. These patterns can be interpreted as truth, and are authorized as aesthetic and ethical criteria. Events that leave behind perceivable physical or virtual remains can be traced back through data. Marks are no longer considered data once the link between the mark and observation is broken. 

Raw data refers to a collection of numbers, characters, images or other outputs from devices to convert physical quantities into symbols, that are unprocessed. Such data is typically further processed by a human or input into a computer, stored and processed there, or transmitted (output) to another human or computer (possibly through a data cable). Raw data is a relative term; data processing commonly occurs by stages, and the "processed data" from one stage may be considered the "raw data" of the next.

Mechanical computing devices are classified according to the means by which they represent data. An analog computer represents a datum as a voltage, distance, position, or other physical quantity. A digital computer represents a datum as a sequence of symbols drawn from a fixed alphabet. The most common digital computers use a binary alphabet, that is, an alphabet of two characters, typically denoted "0" and "1". More familiar representations, such as numbers or letters, are then constructed from the binary alphabet.

Some special forms of data are distinguished. A computer program is a collection of data, which can be interpreted as instructions. Most computer languages make a distinction between programs and the other data on which programs operate, but in some languages, notably Lisp and similar languages, programs are essentially indistinguishable from other data. It is also useful to distinguish metadata, that is, a description of other data. A similar yet earlier term for metadata is "ancillary data." The prototypical example of metadata is the library catalog, which is a description of the contents of books.

Experimental data refers to data generated within the context of a scientific investigation by observation and recording. Field data refers to raw data collected in an uncontrolled in situ environment.

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(source:wikipedia)