Data hierarchy
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Data hierarchy refers to the systematic organization of data, often in a hierarchical form. Data organization involves characters, fields, records, files and so on.[1][2]
A data field holds a single fact or attribute of an entity. Consider a date field, e.g. "19 September 2004". This can be treated as a single date field (e.g. birthdate), or three fields, namely, day of month, month and year.
A record is a collection of related fields. An Employee record may contain a name field(s), address fields, birthdate field and so on.
A file is a collection of related records. If there are 100 employees, then each employee would have a record (e.g. called Employee Personal Details record) and the collection of 100 such records would constitute a file (in this case, called Employee Personal Details file).
Files are integrated into a database.[3] This is done using a Database Management System.[2] If there are other facets of employee data that we wish to capture, then other files such as Employee Training History file and Employee Work History file could be created as well.
An illustration of the above description is shown in this diagram below.
The following terms are for better clarity.
With reference to the example in the above diagram.
Data field label = Employee Name or EMP_NAME
Data field value = Jeffrey Tan
The above description is a view of data as understood by a user e.g. a person working in Human Resource Department.
The above structure can be seen in the hierarchical model, which is one way to organize data in a database.[4]
In terms of data storage, data fields are made of bytes and these in turn are made up of bits.
See also
References
- ^ Blaauw, Gerrit Anne; Brooks, Jr., Frederick Phillips; Buchholz, Werner (1962), "4: Natural Data Units", in Buchholz, Werner (ed.), Planning a Computer System – Project Stretch (PDF), McGraw-Hill Book Company, Inc. / The Maple Press Company, York, PA., pp. 39–40, LCCN 61-10466, archived from the original (PDF) on 2017-04-03, retrieved 2017-04-03,
[…] Terms used here to describe the structure imposed by the machine design, in addition to bit, are listed below.
Byte denotes a group of bits used to encode a character, or the number of bits transmitted in parallel to and from input-output units. A term other than character is used here because a given character may be represented in different applications by more than one code, and different codes may use different numbers of bits (i.e., different byte sizes). In input-output transmission the grouping of bits may be completely arbitrary and have no relation to actual characters. (The term is coined from bite, but respelled to avoid accidental mutation to bit.)
A word consists of the number of data bits transmitted in parallel from or to memory in one memory cycle. Word size is thus defined as a structural property of the memory. (The term catena was coined for this purpose by the designers of the Bull GAMMA 60 computer.)
Block refers to the number of words transmitted to or from an input-output unit in response to a single input-output instruction. Block size is a structural property of an input-output unit; it may have been fixed by the design or left to be varied by the program. […]{{citation}}: Unknown parameter|dead-url=ignored (|url-status=suggested) (help) - ^ a b Laudon, Kenneth C. (2007). Management Information Systems. Upper Saddle River, USA: Pearson. pp. 226, 229. ISBN 978-0-13-157984-2.
- ^ Marston, Tony. "The Relational Data Model - Normalisation and Effective Database Design".
- ^ Cite error: The named reference
Laudon 2007was invoked but never defined (see the help page).