ISO/IEC TR 20943-3:2004
(Main)Information technology — Procedures for achieving metadata registry content consistency — Part 3: Value domains
Information technology — Procedures for achieving metadata registry content consistency — Part 3: Value domains
The purpose of this technical report is to describe a set of procedures for the consistent registration of value domains and their attributes in a registry. This technical report is not a data entry manual, but a user's guide for conceptualizing a value domain and its components for the purpose of consistently establishing good quality metadata. An organization may adapt and/or add to these procedures as necessary.
Technologies de l'information — Procédures pour réaliser la consistance du contenu de l'enregistrement des métadonnées — Partie 3: Domaines de valeur
General Information
Standards Content (Sample)
TECHNICAL ISO/IEC
REPORT TR
20943-3
First edition
2004-03-01
Information technology — Procedures for
achieving metadata registry content
consistency —
Part 3:
Value domains
Technologies de l'information — Procédures pour réaliser
la consistance du contenu de l'enregistrement des métadonnées —
Partie 3: Domaines de valeur
Reference number
ISO/IEC TR 20943-3:2004(E)
©
ISO/IEC 2004
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ISO/IEC TR 20943-3:2004(E)
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ISO/IEC TR 20943-3:2004(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope. 1
1.1 Background. 1
1.2 Purpose. 1
1.3 Limits of this Technical Report . 1
1.4 Registration approach — value domains and data elements. 1
2 Normative references. 1
3 Terms and definitions. 2
4 Understanding value domains. 2
4.1 Introduction. 2
4.2 General principles. 3
4.2.1 Introduction. 3
4.2.2 Choice of codes . 4
4.2.3 Number of permissible values. 4
4.2.4 Conceptual domain hierarchies . 4
4.2.5 Sharing value meanings across permissible values. 5
4.2.6 Sharing value domains across data elements. 5
4.2.7 Associating value domains with concepts (data element concepts and conceptual
domains) . 5
4.2.8 Value domains not associated with data elements .6
4.2.9 Contrasting conceptual domains and data element concepts. 6
4.2.10 Non-enumerated value domains . 6
4.2.11 Value domains with enumerated and non-enumerated components. 7
4.2.12 Semantic restriction of use of value domains . 8
4.2.13 Rapidly changing enumerated value domains (UPC example). 8
4.3 Structure in value domains. 9
4.3.1 Introduction. 9
4.3.2 International Standard Industrial Classification (ISIC). 9
4.3.3 Logical Observation Identifiers Names and Codes (LOINC) . 11
4.4 Code sets as value domains. 12
4.5 Classification schemes as value domains . 13
4.6 Data types and value domains . 15
4.6.1 Basics. 15
4.6.2 Value domains with more than one data type — limitations of value meaning . 15
4.7 Units of measure . 16
4.8 Dimensionality. 18
4.9 Classifying value domains. 19
5 Registering value domains . 20
5.1 Introduction. 20
5.2 Rules for registering value domains. 20
5.3 Strategies. 23
5.4 Examples. 23
5.4.1 Enumerated value domain . 24
5.4.2 Non-enumerated value domain . 30
Annex A Metamodel for value domains and conceptual domains . 33
Bibliography . 35
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ISO/IEC TR 20943-3:2004(E)
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are members of
ISO or IEC participate in the development of International Standards through technical committees
established by the respective organization to deal with particular fields of technical activity. ISO and IEC
technical committees collaborate in fields of mutual interest. Other international organizations, governmental
and non-governmental, in liaison with ISO and IEC, also take part in the work. In the field of information
technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of the joint technical committee is to prepare International Standards. Draft International
Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as
an International Standard requires approval by at least 75 % of the national bodies casting a vote.
In exceptional circumstances, the joint technical committee may propose the publication of a Technical Report
of one of the following types:
— type 1, when the required support cannot be obtained for the publication of an International Standard,
despite repeated efforts;
— type 2, when the subject is still under technical development or where for any other reason there is the
future but not immediate possibility of an agreement on an International Standard;
— type 3, when the joint technical committee has collected data of a different kind from that which is normally
published as an International Standard (“state of the art”, for example).
Technical Reports of types 1 and 2 are subject to review within three years of publication, to decide whether
they can be transformed into International Standards. Technical Reports of type 3 do not necessarily have to
be reviewed until the data they provide are considered to be no longer valid or useful.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights.
ISO/IEC TR 20943-2, which is a Technical Report of type 3, was prepared by Joint Technical Committee
ISO/IEC JTC 1, Information technology, Subcommittee SC 32, Data management and interchange.
ISO/IEC 20943 consists of the following parts, under the general title Information technology — Procedures
for achieving metadata registry content consistency:
Part 1: Data elements [Technical Report]
Part 3: Value domains [Technical Report]
The following parts are under preparation:
Part 2: XML structured data
Part 4: Overview
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ISO/IEC TR 20943-3:2004(E)
Introduction
The exchange of metadata between metadata registries based on ISO/IEC 11179, Information technology —
Metadata registries (all parts), depends not only on registry software that conforms to the standard, but also
on metadata contents that are comparable between registries. While the standard has provisions for data
specification and registration, there are pragmatic issues pertaining to populating the registries with content.
Based on the experiences of organizations that are implementing the standard, technical reports to explore
content issues will help current and future users.
Metadata registries can be used to register data elements, value domains, other objects, and associated
attributes for many kinds of organizational data resource collections. Metadata registries can store information
describing value domains used to specify the allowed values of a data element, the codes in a standard list,
and classification schemes.
This technical report is based on ISO/IEC 11179-3:2003 of the six-part ISO/IEC 11179 International Standard
that describes the organization of a registry for managing the semantics of data. The standard specifies the
structure of a registry in the form of a conceptual model. The conceptual model is not intended to be a logical
or physical data model for a computer system.
ISO/IEC 11179-3:2003, models a value domain and an associated conceptual domain. Conceptualization and
articulation of rules and relationships are needed in the creation of conceptual domains and value domains.
Reuse of value domains should be enabled and regularized. Elementarily equivalent domains have a
relationship between their values that needs to be captured in a metadata registry. Some conceptually
equivalent domains have relationships between their values, too. These also need to be captured. This
Technical Report describes how this can be accomplished.
While metadata registries can be used for storing information about a variety of metadata items, this Technical
Report addresses only value domains, conceptual domains, and their associated attributes and relationships.
The goal of this paper is to ensure that there is a common understanding of the content of the value domain
attributes so that metadata can be shared between registries, despite their differences.
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TECHNICAL REPORT ISO/IEC TR 20943-3:2004(E)
Information technology — Procedures for achieving metadata
registry content consistency —
Part 3:
Value domains
1 Scope
1.1 Background
An ISO/IEC 11179 metadata registry (MDR) is a tool for the management of shareable data; a comprehensive,
authoritative source of reference information about data. It supports the standardization and harmonization
processes by recording and disseminating descriptions of data, which facilitates data sharing among
organizations and users. It provides links to documents that refer to specific data elements, value domains,
and classification schemes and to information systems where those objects are used. When used in
conjunction with a database, the registry enables users to understand any information obtained from the
database better.
A registry does not contain data itself. It contains the metadata that is necessary to clearly describe, inventory,
analyse, and classify data. It provides an understanding of the meaning, representation, and identification of
units of data. This International Standard identifies the information elements that need to be available for
determining the meaning of data to be shared between systems.
1.2 Purpose
The purpose of this Technical Report is to describe a set of procedures for the consistent registration of value
domains and their attributes in a registry. This Technical Report is not a data entry manual, but a user’s guide
for conceptualizing a value domain and its components for the purpose of consistently establishing good
quality metadata. An organization may adapt and/or add to these procedures as necessary.
1.3 Limits of this Technical Report
The scope of this Technical Report is limited to value domains, conceptual domains, and their associated
attributes and relationships. Examples are used throughout the TR to illustrate the concepts described.
1.4 Registration approach — value domains and data elements
There is a choice when registering value domains in an MDR. Some Registration Authorities treat these sets
as value domains, and others treat them as data elements. For the purposes of this Technical Report, the
choice will always be to treat the sets as value domains unless explicitly stated. This choice is made to help
illustrate the way to register many different kinds of value domains.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
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ISO/IEC TR 20943-3:2004(E)
ISO/IEC 11179-1, Information technology — Metadata registries (MDR) — Part 1: Framework for the
specification and standardization of data elements
ISO/IEC 11179-2, Information technology — Specification and standardization of data elements — Part 2:
Classification for data elements
ISO/IEC 11179-3, Information technology — Metadata registries — Part 3: Registry metamodel and basic
attributes
ISO/IEC 11179-4, Information technology — Metadata registries (MDR) — Part 4: Rules and guidelines for the
formulation of data definitions
ISO/IEC 11179-5, Information technology — Specification and standardization of data elements — Part 5:
Naming and identification principles for data elements
ISO/IEC 11179-6, Information technology — Metadata registries (MDR) — Part 6: Registration of data
elements
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC 11179 and the following apply.
3.1
conceptually equivalent domains
value domains that represent the same conceptual domain
3.2
elementarily equivalent domains
domains that are elementarily equivalent if there exists a one-to-one correspondence between their
permissible values such that given any pair of corresponding permissible values their value meanings are
equal
NOTE 1 See Example in 4.2.5.
NOTE 2 All elementarily equivalent domains are conceptually equivalent. This follows from the fact that elementarily
equivalent domains have the same set of value meanings, therefore they represent the same conceptual domain.
NOTE 3 Elementarily equivalence is an equivalence relation on the set of all enumerated value domains. So, any
number of enumerated value domains may be elementarily equivalent to each other. See Examples in 5.4.1.
4 Understanding value domains
4.1 Introduction
This section is devoted to describing several things about value domains:
1) Some general principles about value domains
2) The structure or relationships that exist in some value domains
3) Code sets as value domains
4) Classification schemes as value domains
5) The relationship of data types to value domains
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ISO/IEC TR 20943-3:2004(E)
6) Use of units of measure
7) The importance of dimensionality
8) Classifying value domains
Examples are used throughout to illustrate the ideas. See Annex A for a detailed model (from
ISO/IEC 11179-3) illustrating the relationships among all the constructs described herein.
4.2 General principles
4.2.1 Introduction
A Value Domain is a set of permissible values. A Permissible Value is a combination of some value and the
meaning for that value. The associated meaning is called the Value Meaning. A permissible value is
represented in this Technical Report as an ordered pair delimited by angle brackets as follows:
meaning>. A value domain is the set of valid values for one or more data elements. It is used for validation of
data in information systems and in data exchange. It is also an integral part of the metadata needed to
describe a data element. In particular, a value domain is a guide to the content, form, and structure of the data
represented by a data element.
Value domains come in two main types: enumerated and non-enumerated. An Enumerated Value Domain is a
value domain where all the permissible values are listed explicitly. Examples of types of enumerated value
domains include code sets, standard classifications, and categorizations. A Non-enumerated Value Domain is
a value domain where the permissible values are expressed using a rule, called a Non-enumerated Value
Domain Description. Thus, the permissible values are listed implicitly. This rule specifies precisely which
values belong to the value domain and which do not. Examples of types of non-enumerated value domains
include intervals of numbers, character strings, and bit maps.
A Conceptual Domain is a set of value meanings. It is a concept for which the extension is a collection of
value domains. Conceptual domains, too, come in two main types: enumerated and non-enumerated. The
value meanings for an Enumerated Conceptual Domain are listed explicitly. This type of conceptual domain
corresponds to the enumerated type for value domains. The value meanings for a Non-enumerated
Conceptual Domain are expressed using a rule, called a Non-enumerated Conceptual Domain Description.
Thus, the value meanings are listed implicitly. This rule describes the meaning of permissible values in a non-
enumerated value domain. This type of conceptual domain corresponds to the non-enumerated type for value
domains.
Every value domain represents two kinds of concepts: data element concept (indirectly) and conceptual
domain (directly). The Data Element Concept is the concept associated with a data element. The value
domain is the representation for the data element, and, therefore, indirectly represents the data element
concept, too. However, the value domain is directly associated with a conceptual domain, so represents that
concept, independent of any data element.
An example will help to illustrate the distinctions in the discussion, which is shown below:
EXAMPLE
Data element name: Sex of employee – code
Data element concept name: Sex of employee
Data element concept definition: The sex of the employee of an organization.
Conceptual domain name: Human sex categories
Conceptual domain definition: Enumerations of human sexes.
Value domain name: Human sex codes (1)
Value domain definition: Codes for the human sexes.
Permissible values: <1, Male>
<2, Female>
<0, Unknown>
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ISO/IEC TR 20943-3:2004(E)
The codes used in the value domain above are taken from ISO/IEC 5218. Using standardized codes ensures
interoperability between metadata registries and application systems. However, in general, the choice of
codes for a value domain may be arbitrary. In this case, the MDR is the source for obtaining the values and
their meanings for a non-standard value domain.
Several points about value domains need to be made here.
4.2.2 Choice of codes
The choice of codes used in the value domain above is arbitrary. Another code set might work just as well, but
the set is a different value domain. Which value domain to use is determined by the needs of the application
and the organization. The following example is another code set for human sex codes:
EXAMPLE
Value domain name: Human sex codes (2)
Value domain definition: Codes for the human sexes.
Permissible values:
4.2.3 Number of permissible values
The number of permissible values (3 in our example) may also be different. We might want a code for
representing hermaphrodites or a code for representing transsexuals. Each time new permissible values are
added or subtracted, a new value domain, or value domain version, is created. Determining whether a change
to a value domain merits the creation of a new value domain or just a new version of an existing value domain
is up to the individual registration authority. The following example shows an expanded value domain
considered as a new one, not a version of an old one, as in the example in 4.2.2.
EXAMPLE
Value domain name: Human sex codes (3)
Value domain definition: Codes for the human sexes.
Permissible values:
4.2.4 Conceptual domain hierarchies
All the value domains for human sex codes can be viewed as being conceptually equivalent. There is no
requirement that each of the value meanings in a conceptual domain be associated with a value. However,
some Registration Authorities may decide that to adequately differentiate the concept, for example, of using
five categories of human sex codes instead of three, separate conceptual domains must be created. See
example below. At the highest level, all the value domains (examples in 4.2.1, 4.2.2, and 4.2.3) represent the
idea of categories of human sexes. So, the super-ordinate conceptual domain captures the concept
represented by a class of value domains (e.g., human sex codes) needed within a registry. The subordinate
conceptual domains provide the enumeration of value meanings to be mapped to the corresponding value
domains.
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ISO/IEC TR 20943-3:2004(E)
EXAMPLE
Super-ordinate conceptual domain (non-enumerated)
Conceptual domain name: Human sex categories
Conceptual domain definition: Categorizations of human sexes.
Subordinate conceptual domain (1) (enumerated)
Conceptual domain name: Human sex categories: 3 values
Conceptual domain definition: Enumerations of human sexes with 3 categories.
Subordinate conceptual domain (2) (enumerated)
Conceptual domain name: Human sex categories: 5 values
Conceptual domain definition: Enumerations of human sexes with 5 categories
4.2.5 Sharing value meanings across permissible values
The value meaning is used to link equivalent permissible values across conceptually equivalent domains. In elementarily
equivalent domains, each value meaning links equivalent codes between a unique pair of permissible values, one from
each value domain, as the following example illustrates:
EXAMPLE
Conceptual domain name: Human sex categories
Conceptual domain definition: Enumerations of human sexes.
Value domain names: Human sex codes (1) (See Example, 4.2.1)
Human sex codes (2) (See Example, 4.2.2)
Value domain definition: Codes for the human sexes.
A one-to-one correspondence that preserves value meanings between these two enumerated value domains is defined as
follows:
HSC(1) |Æ HSC(2)
<1, Male> ↔
<2, Female> ↔
<0, Unknown> ↔
Each pair of corresponding permissible values has the same value meaning. So, these two enumerated value domains
are elementarily equivalent and, therefore, conceptually equivalent.
Each permissible value in one of the two value domains listed above shares its value meaning with that of a
permissible value in the other value domain. So, through the use of value meanings, equivalence of values
across value domains is achievable, e.g., the values 1 and M mean Male or the values 2 and F mean Female.
These two value domains are elementarily equivalent domains.
4.2.6 Sharing value domains across data elements
Sex of employee (the idea that employees are classified or characterized by sex) and sex of student (the idea
that students are classified or characterized by sex) are different data element concepts, but they could use
the same value domain to represent them. So, a value domain (e.g., Human Sex Codes (1)) may be
associated with many data element concepts, and, therefore, data elements.
4.2.7 Associating value domains with concepts (data element concepts and conceptual domains)
A data element concept is associated with different value domains as needed to describe similar, but different,
data elements, and those value domains are conceptualized by the same conceptual domain (e.g., Human
Sex Codes (1), Human Sex Codes (2), Human Sex Codes (3) in the examples). However, the converse is not
true: two value domains under the same conceptual domain do not need to be associated with the same data
element concept. The following two examples (1 and 2) are of this type:
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ISO/IEC TR 20943-3:2004(E)
EXAMPLE 1
Conceptual domain name: Human sex categories
Conceptual domain definition: Enumerations of human sexes.
Value domain name: Human sex codes (1) (See Example in 4.2.1)
Value domain definition: Codes for the human sexes.
Data element concept name: Sex of employee
Data element concept definition: The biological sex of the employee of an organization.
EXAMPLE 2
Conceptual domain name: Human sex categories
Conceptual domain definition: Enumerations of human sexes.
Value domain name: Human sex codes (2) (See Example in 4.2.2)
Value domain definition: Codes for the human sexes.
Data element concept name: Sex of student
Data element concept definition: The biological sex of the student of an educational institution.
4.2.8 Value domains not associated with data elements
Value domains
...
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