data hierarchy

The system of data objects which provide the methods for

information storage and retrieval. Broadly, a data

hierarchy may be considered to be either natural, which arises

from the alphabet or syntax of the language in which the

information is expressed, or machine, which reflects the

facilities of the computer, both hardware and software.

A natural data hierarchy might consist of bits,

characters, words, phrases, sentences, paragraphs, and

chapters. One might use components bound to an application,

such as field, record, and file, and these would ordinarily be

further specified by having data descriptors such as name

field, address field, etc. On the other hand, a machine or

software system might use bit, byte, word, block,

partition, channel, and port.

Programming languages often provide types or objects which

can create data hierarchies of arbitrary complexity, thus

allowing software system designers to model language

structures described by the linguist to greater or lesser

degree.

The distinction between the natural form of data and the

facilities provided by the machine may be obscure, because

users force their needs into the molds provided, and

programmers change machine designs. As an example, the

natural data type "character" and the machine type "byte" are

often used interchangably, because the latter has evolved to

meet the need of representing the former.

(1995-11-03)