representation term A representation term is a word, or a combination of words, that semantically represent the data type (value domain) of a data element. A representation term is commonly referred to as a ''class word'' by those familiar with data dictionaries. ISO ...

is a word, or a combination of words, used as part of a

data element name A data element name is a name given to a data element in, for example, a data dictionary or metadata registry. In a formal data dictionary, there is often a requirement that no two data elements may have the same name, to allow the data element na ...

. ''Representation class'' is sometimes used as a

synonym A synonym is a word, morpheme, or phrase that means exactly or nearly the same as another word, morpheme, or phrase in a given language. For example, in the English language, the words ''begin'', ''start'', ''commence'', and ''initiate'' are all ...

for representation term. In

ISO/IEC 11179 The ISO/IEC 11179 Metadata Registry (MDR) standard is an international ISO/IEC standard for representing metadata for an organization in a metadata registry. It documents the standardization and registration of metadata to make data understandabl ...

, a ''representation class'' provides a way to classify or group

data element In metadata, the term data element is an atomic unit of data that has precise meaning or precise semantics. A data element has: # An identification such as a data element name # A clear data element definition # One or more representation terms # ...

s. A ''representation class'' is effectively a specialized

classification scheme In information science and ontology, a classification scheme is the product of arranging things into kinds of things (classes) or into ''groups'' of classes; this bears similarity to categorization, but with perhaps a more theoretical bent, as cla ...

. Hence, there is currently some discussion in ISO over the merits of keeping representation class as a separate entity in 11179, versus collapsing it into the general classification scheme facility. A clear distinction between the two mechanisms, however, is that 11179 allows a data element to be classified by only one representation class, whereas there is no such restriction on other classification schemes. ISO/IEC 11179 does not specify that ''representation terms'' should be drawn from the values of ''representation class'', though it would make sense to do so, nor does it provide any mechanism to ensure any sort of consistency (whatever that might mean) between the representation terms used to name a data element, and the representation class used to classify it. The term ''representation class'' has been used in metadata registry standards for many years. Today it has a combination of meanings and now goes well beyond how a

is represented in a

computer system A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations (computation) automatically. Modern digital electronic computers can perform generic sets of operations known as programs. These progr ...

. In practice this term is used to shed light on the

semantics Semantics (from grc, σημαντικός ''sēmantikós'', "significant") is the study of reference, meaning, or truth. The term can be used to refer to subfields of several distinct disciplines, including philosophy Philosophy (f ...

or meaning of the data element.

Definitions of "representation class"

There are several alternate definitions for ''representation class''. Some of these are taken from the ISO documents. Note that these documents are copyrighted and extracts can only be taken under the fair use rules.

ISO Definitions of representation class

From ISO/IEC TR 20943-1 First edition 2003-08-01 pdf page 91

B.2.3 Representation class Representation class is the value domain for representation. The set of classes make it easy to distinguish among the elements in the registry. For instance, a data element categorized with the representation class amount is different from an element categorized as number. It probably will not make sense to compare the contents of these elements, or perform calculations using them together. Representation class is a mechanism by which the functional and/or presentational category of an item may be conveyed to the user.

From ISO/IEC 11179-3 Second edition 2003-02-15

3.3.51 data element representation class the class of representation of a data element

Notes

# {{note, Issue114
Link to the ISO bugzilla discussion of Representation class

External links

ISO/IEC TR 20943-1:2003(E) Procedures for Achieving Metadata Registry Content Consistency — Part 1: Data elements
br>(page 84) (700K zip file)
ISO/IEC 11179-1 Metadata registries (MDR) — Part 1: Framework
(233K zip file)
ISO/IEC 11179-3 Metadata registries (MDR) — Part 3: Registry metamodel and basic attributes
(546K zip file)
ISO/IEC 11179-5 Metadata registries (MDR) — Part 5: Naming and identification principles
(238K zip file)
DOJ and GJXDM training slides on naming
ISO/IEC 11179 Metadata Metadata registry