SIST ISO 25964-2:2013

INTERNATIONAL ISO
STANDARD 25964-2
First edition
2013-03-15
Information and documentation —
Thesauri and interoperability with other
vocabularies —
Part 2:
Interoperability with other vocabularies
Information et documentation — Thésaurus et interopérabilité avec
d'autres vocabulaires —
Partie 2: Interopérabilité avec d'autres vocabulaires

Reference number
©
ISO 2013
©  ISO 2013
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,
electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or
ISO's member body in the country of the requester.
ISO copyright office
Case postale 56  CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2013 – All rights reserved

Contents Page
Foreword . v
Introduction . vi
1  Scope . 1
2  Normative references . 1
3  Terms and definitions . 1
4  Symbols, abbreviations and other conventions . 15
5  Objectives and identification . 16
5.1  Objectives of interoperability and mapping . 16
5.2  Identifying the elements to be mapped . 16
6  Structural models for mapping across vocabularies . 16
6.1  General . 16
6.2  Model 1: Structural unity . 17
6.3  Model 2: Direct-linked . 17
6.4  Model 3: Hub structure . 17
6.5  Selective mapping . 19
6.6  Choosing among the options . 20
7  Types of mapping . 20
7.1  General . 20
8  Equivalence mappings. 21
8.1  General . 21
8.2  Simple equivalence . 21
8.3  Compound equivalence . 22
9  Hierarchical mappings . 25
10  Associative mappings. 25
11  Exact, inexact and partial equivalence. 26
11.1  General . 26
11.2  Exact equivalence . 26
11.3  Inexact equivalence . 27
11.4  Partial equivalence . 27
12  Use of mappings in information retrieval . 28
12.1  General . 28
12.2  Human mediation . 28
12.3  Examples of mapping implementation . 29
12.4  Conclusions and recommendations . 30
13  Handling pre-coordination . 31
13.1  General . 31
13.2  Mapping between a thesaurus and a scheme with context-dependent captions . 32
13.3  Mapping more complex classes . 37
14  Techniques for identifying candidate mappings . 38
14.1  General procedure . 38
14.2  Computer assisted direct matching . 40
14.3  Co-occurrence mapping . 40
14.4  Other methods . 40
15  Managing the data . 41
15.1  Types of data to be recorded . 41
15.2  Storing the data . 43
15.3  Maintaining the mappings data . 43
16  Display of mapped vocabularies .45
16.1  General .45
16.2  Single record display .46
16.3  Complete displays based on one of the vocabularies .48
16.4  Crosswalks .49
17  Classification schemes .50
17.1  Key characteristics and background .50
17.2  Semantic components and relationships compared with thesaurus components .53
17.3  Recommendations for mapping between a thesaurus and a classification scheme .55
18  Classification schemes used for records management .56
18.1  Key characteristics and background .56
18.2  Semantic components and relationships compared with thesaurus components .57
18.3  Recommendations for interoperability with a thesaurus .58
19  Taxonomies .59
19.1  Key characteristics and background .59
19.2  Types of taxonomies .60
19.3  Semantic components and relationships .61
19.4  Mapping between a thesaurus and a taxonomy .63
20  Subject heading schemes .67
20.1  Key characteristics and background .67
20.2  Semantic components and relationships .68
20.3  Mapping subject headings to and from thesaurus concepts .69
21  Ontologies .72
21.1  Key characteristics and background .72
21.2  Semantic components and relationships .73
21.3  Structural comparison between thesauri and ontologies .76
21.4  Interoperability with thesauri .77
22  Terminologies .78
22.1  Key characteristics and background .78
22.2  Semantic components and relationships compared with those of a thesaurus .79
22.3  Interoperability with thesauri .81
23  Name authority lists .81
23.1  Key characteristics and background .81
23.2  Semantic components and relationships .83
23.3  Mapping between a thesaurus and a name authority list .85
24  Synonym rings .87
24.1  Key characteristics and background .87
24.2  Semantic components and relationships .88
24.3  Interoperability with thesauri .89
Annex A (informative) Management of terminological data in support of interoperability .90
Bibliography .93
Index .96

iv © ISO 2013 – All rights reserved

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 25964-2 was prepared by Technical Committee ISO/TC 46, Information and documentation,
Subcommittee SC 9, Identification and description.
ISO 25964-1:2011, Clauses 1 to 13, correspond broadly to the content of ISO 2788:1986 and ISO 5964:1985.
The remaining clauses of ISO 25964-1, and the whole of this part of ISO 25964, cover new ground not
previously covered in any International Standard.
ISO 25964 consists of the following parts, under the general title Information and documentation — Thesauri
and interoperability with other vocabularies:
— Part 1: Thesauri for information retrieval
— Part 2: Interoperability with other vocabularies
ISO 25964-1 covers the development and maintenance of thesauri, both monolingual and multilingual,
including formats and protocols for data exchange.
This part of ISO 25964 covers interoperability between different thesauri and with other types of structured
vocabulary.
ISO 25964 covers development and maintenance of thesauri rather than how to use them in indexing, which
is covered by ISO 999.
Introduction
The ability to identify and locate relevant information among vast collections and other resources is a major
and pressing challenge today, hence the need for semantic interoperability. To support this need, a variety of
web services and other tools are under active development, including (but not limited to):
 registries of vocabularies and metadata schemas,
 repositories of vocabularies and metadata schemas, and
 crosswalk services.
While registries and repositories are outside the scope, this International Standard provides guidance
fundamental to the establishment of crosswalk services. Typically these rely on mapping between different
schemas and vocabularies. Accordingly, inter-vocabulary mapping will be the principal focus of this part of
ISO 25964.
The foundation for discussion of interoperability is laid in ISO 25964-1, which describes the key characteristics
of thesauri and provides guidance on best practice. Unfortunately, however, a comparable International
Standard does not exist for the other types of vocabulary with which a thesaurus needs to interoperate. For
this reason, this second part of ISO 25964 provides some elementary description of other vocabularies such
as classification schemes, subject heading schemes, etc., before making recommendations on mapping
between these and thesauri. It does not provide guidance on the construction of vocabularies other than
thesauri.
Clauses 1 to 12 and Clauses 14 to 16 of this part of ISO 25964 deal with the principles and practicalities of
interoperability, especially mapping, that apply to most vocabularies and especially thesauri. Clause 13
provides additional guidance for handling the pre-coordinated classes that occur in classification schemes and
other vocabularies using the classification approach.
Clauses 17 to 24 are each dedicated to a different type of vocabulary. First priority is given to vocabularies
that are commonly used for classifying or indexing resources, namely classification schemes (including those
used for records management), taxonomies, subject heading schemes and name authority lists.
Notwithstanding their different purposes, terminologies, ontologies and synonym rings are also included. Each
clause provides a brief informative description of the vocabulary’s key characteristics, contrasting its semantic
components with those of a thesaurus, so as to provide context for the interoperability requirements and
recommendations that follow.
vi © ISO 2013 – All rights reserved

INTERNATIONAL STANDARD ISO 25964-2:2013(E)

Information and documentation — Thesauri and interoperability
with other vocabularies —
Part 2:
Interoperability with other vocabularies
1 Scope
This part of ISO 25964 is applicable to thesauri and other types of vocabulary that are commonly used for
information retrieval. It describes, compares and contrasts the elements and features of these vocabularies
that are implicated when interoperability is needed. It gives recommendations for the establishment and
maintenance of mappings between multiple thesauri, or between thesauri and other types of vocabularies.
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.
ISO 25964-1:2011, Information and documentation — Thesauri and interoperability with other vocabularies —
Part 1: Thesauri for information retrieval
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
array
group of sibling concepts (3.17)
EXAMPLE
In the following, the sibling concepts outerwear and underwear form an array within the concept clothing.
clothing
outerwear
overcoats
underwear
3.2
associative relationship
relationship between a pair of concepts (3.17) that are not related hierarchically but share a strong semantic
connection
3.3
broader term
preferred term (3.62) representing a concept (3.17) that is broader than the one in question
NOTE The scope of the narrower concept falls completely within the scope of the broader. The relationship between
the two is commonly indicated with the tag BT. For more explanation see ISO 25964-1:2011, 10.2.1.
3.4
caption
text label of the class (3.10) represented by a notation (3.54) in a classification scheme (3.12)
NOTE A caption is read in conjunction with its hierarchical context. It does not need to be as complete or as
self-contained as a scope note or even a preferred term in a thesaurus. Captions are sometimes known as class headings
or class names.
3.5
category
concept (3.17) or group of similar or related concepts (3.17) used as a division or subdivision in a taxonomy
(3.83)
NOTE 1 In a classification scheme, such a group is normally called a class.
NOTE 2 This definition of category should not be confused with “fundamental categories”, discussed in
ISO 25964-1:2011 (for example in Clause 12) in the context of faceted classification.
3.6
category label
text label representing a category (3.5) in a taxonomy (3.83)
NOTE The category label in a taxonomy is comparable to the caption in a classification scheme, and although a
category is often referred to as a node, a category label should not be confused with a node label.
3.7
chain index
index to a scheme that represents compound concepts (3.17) by a string of pre-coordinated (3.60) terms
(3.84), such as a classification scheme (3.12), in which entries are generated by successive left truncation
of strings of terms (3.84) representing complex concepts (3.17)
NOTE See the example in 17.2.4, Figure 12.
3.8
characteristic of division
attribute by which a concept (3.17) can be subdivided into an array (3.1) of narrower concepts (3.17) each
having a distinct value of that attribute
cf. node label (3.52)
EXAMPLE
In the following, age group is the characteristic of division applied to the concept of people.
people
(people by age group)
children
youths
adults
3.9
citation order
order in which preferred terms (3.62) or notations (3.54) are combined in a pre-coordinate (3.60) indexing
(3.36) system or a classification scheme (3.12) to form strings representing complex concepts (3.17)
2 © ISO 2013 – All rights reserved

3.10
class
concept (3.17) or group of similar or related concepts (3.17) used as a division or subdivision in a
classification scheme (3.12)
NOTE Classes are the basic units of which a classification scheme is constructed. In a taxonomy, although this is a
type of classification scheme, they are generally known as categories (see 3.5). Occasionally they are described as
“nodes”, although they should not be confused with node labels. The term “class” has a different meaning in the context of
ontologies. See 21.2.2.
3.11
classification
classifying
activity involving the components of grouping similar or related things together, separating dissimilar or
unrelated things, and arranging the resulting classes (3.10) in a logical and helpful sequence
3.12
classification scheme
schedule (3.67) of concepts (3.17) and pre-coordinated (3.60) combinations of concepts (3.17), arranged
by classification (3.11)
NOTE A classification scheme often also includes an index.
3.13
collection
set of information resources that can or could be accessed by a structured vocabulary (3.74), whether the
items in the set are collected in one place or distributed over a network
3.14
compound equivalence
relationship between terms (3.84) or mapping (3.41) between concepts (3.17) in which one term (3.84) or
concept (3.17) in one context is represented by two or more terms (3.84) or concepts (3.17) in another
3.15
compound heading
pre-coordinated heading
subject heading (3.76) formed by pre-coordination (3.60) of more than one term (3.84) into a string
EXAMPLE
The single terms Buddhism, Mass media and Religious aspects may be combined to form the compound heading
Mass media — Religious aspects — Buddhism.
3.16
compound term
term (3.84) that can be split morphologically into separate components
EXAMPLES
In English:
“copper mines” can be split into “copper” and “mines”
“lawnmowers” can be split into “lawns” and “mowers”
In French:
“mine de cuivre” can be split into “mine” and “cuivre”
“biodiversité” can be split into “biologie” and “diversité”

NOTE Compound terms can be multi-word terms, or can consist of only one word.
3.17
concept
unit of thought
NOTE Concepts can be expressed in a variety of different ways. They exist in the mind as abstract entities
independent of terms used to express them. They range from the very simple, e.g. “child”, to the very complex, e.g. “child
protection legislation”.
3.18
concept group
group of concepts (3.17) selected by some specified criterion, such as relevance to a particular subject area
3.19
controlled vocabulary
prescribed list of terms (3.84), headings or codes, each representing a concept (3.17)
NOTE Controlled vocabularies are designed for applications in which it is useful to identify each concept with one
consistent label, for example when classifying documents, indexing them and/or searching them. Thesauri, subject
heading schemes and name authority lists are examples of controlled vocabularies.
cf. terminology (3.85)
3.20
cross-language equivalence
equivalence relationship (3.28) between terms (3.84) representing the same concept (3.17) in different
languages
3.21
crosswalk
table of mappings (3.41) between the concepts (3.17) in two or more structured vocabularies (3.74)
NOTE Crosswalks support the ability of search engines to search effectively across heterogeneous databases.
3.22
data model
abstract model that describes how data is represented and used
NOTE The data model in ISO 25964-1 provides a generic definition of thesaurus structure and semantics. It can be
used as the basis for defining a database model or an exchange format for thesauri.
3.23
differentiated mapping
mapping (3.40) methodology that aims to distinguish between different types and qualities of mapping (3.41)
NOTE Types of mapping that can be distinguished include equivalence, associative and hierarchical; equivalence
can be further subdivided into simple or compound, and the degree of equivalence can be marked to support further
distinctions at the time of use.
cf. undifferentiated mapping (3.88)
3.24
document
any resource that can be classified (3.11) or indexed in order that the data or information in it may be
retrieved
NOTE This definition refers not only to written and printed materials in paper or microform versions (for example,
conventional books, journals, diagrams, maps), but also to non-printed media such as machine-readable and digitized
records, internet and intranet resources, films, sound recordings, people and organizations as knowledge resources,
buildings, sites, monuments, three-dimensional objects or realia; and collections of such items or parts of such items.
4 © ISO 2013 – All rights reserved

3.25
entry term
lead-in term
term (3.84) provided in a controlled vocabulary (3.19), not for direct use in metadata (3.45), but for the
purpose of guiding the user to another term (3.84) which may be used as a category label (3.6), subject
heading (3.76) or preferred term (3.62)
NOTE Entry terms occurring in a thesaurus are generally known as non-preferred terms.
3.26
enumerative classification scheme
classification scheme (3.12) in which all the classes (3.10) available are explicitly listed in the schedules
(3.67)
cf. synthetic classification scheme (3.80)
3.27
equivalence mapping
mapping (3.41) that states that the concept (3.17) in the target vocabulary (3.82) is considered identical in
scope to the concept (3.17) in the source vocabulary (3.72)
cf. equivalence relationship (3.28)
3.28
equivalence relationship
relationship between two terms (3.84) in a thesaurus (3.86) that both represent the same concept (3.17)
NOTE In ordinary discourse, terms that are quasi-synonyms may represent slightly different concepts. After inclusion
in the thesaurus, however, the equivalence relationship clarifies that both are regarded as representing the same concept.
When two or more such terms are in the same language within a monolingual or multilingual thesaurus, one of them is
designated a preferred term and the other(s) as non-preferred term(s); when two or more such terms are in the different
languages of a multilingual thesaurus, each of them may be a preferred term in its own language respectively, and the
relationship is known as cross-language equivalence.
3.29
exchange format
machine-readable format for representing information that is intended to facilitate exchange of the information
between different applications
NOTE The exchange format for a thesaurus often uses a markup language based on a standard such as XML
(Extensible Markup Language), and is based on a data model for thesauri. While the data model provides a generic
description of thesaurus structure and semantics, the exchange format expresses this in a formal language for the
purpose of exchanging thesauri.
3.30
facet
grouping of concepts (3.17) of the same inherent category
EXAMPLE 1
Animals, mice, daffodils and bacteria could all be members of a living organisms facet.

EXAMPLE 2
Digging, writing and cooking could all be members of an actions facet.

EXAMPLE 3
Paris, the United Kingdom and the Alps could all be members of a places facet.
NOTE Examples of high-level categories that can be used for grouping concepts into facets are: objects, materials,
agents, actions, places and times.
cf. node label (3.52)
3.31
faceted classification scheme
classification scheme in which concepts (3.17) are analysed into their constituent facets (3.30)
NOTE Schedules are compiled for each facet, and terms or notations from these are then combined according to
prescribed rules to express a complex concept. Some complex concepts are often enumerated explicitly in the schedules;
others can be synthesized by the user.
3.32
hierarchical relationship
relationship between a pair of concepts (3.17) of which one has a scope falling completely within the scope of
the other
cf. broader term (3.3), narrower term (3.51)
NOTE Several different types of hierarchical relationship exist. For more explanation see ISO 25964-1:2011, 10.2.
3.33
homograph
one of two or more words that are written in the same way, but have different meanings
EXAMPLE
In English:
The word “bank” could refer to a financial institution or the side of a river.
In French:
The word “avocat” could refer to a lawyer or to a fruit.

NOTE Homographs are sometimes referred to as homonyms, although the latter term applies more broadly, as it
also includes pairs of terms such as “weights” and “waits” in English or “mer” and “mère” in French, which sound the same
although they are spelt differently.
3.34
identifier
set of symbols, usually alphanumeric, designating a concept (3.17) or a term (3.84) or another entity for
purposes of unique identification within a determined context or resource, especially in a computer system or
network
NOTE A notation is sometimes used as an identifier.
3.35
index term
term (3.84) assigned to a document (3.24) in the process of indexing (3.36)
NOTE Sometimes index terms are referred to as indexing terms, as keywords or as tags, but the latter terms have
other meanings too. Preferred terms from a thesaurus are very often used as index terms.
6 © ISO 2013 – All rights reserved

3.36
indexing
intellectual analysis of the subject (3.75) matter of a document (3.24) to identify the concepts (3.17)
represented in it, and allocation of the corresponding index terms (3.35) to allow the information to be
retrieved
NOTE The term “subject indexing” is often used for this activity, but as ISO 25964 does not deal with the indexing of
other elements such as authors or dates, “indexing” is sufficient. Indexing can be carried out by human users or by
automated agents.
3.37
information retrieval
all the techniques and processes used to identify documents (3.24) relevant to an information need, from a
collection (3.13) or network of information resources
NOTE Selection and inclusion of items in the collection are included in this definition; likewise browsing and other
forms of information seeking.
3.38
interoperability
ability of two or more systems or components to exchange information and to use the information that has
been exchanged
NOTE Vocabularies can support interoperability by including mappings to other vocabularies, by presenting data in
standard formats and by using systems that support common computer protocols.
3.39
map, verb
establish relationships between the concepts (3.17) of one vocabulary and those of another
3.40
mapping, gerund (verbal noun)
process of establishing relationships between the concepts (3.17) of one vocabulary and those of another
3.41
mapping, noun
product of mapping process relationship between a concept (3.17) in one vocabulary and one or more
concepts (3.17) in another
NOTE 1 A mapping generally has a direction, as discussed in Clause 6.
NOTE 2 Exceptionally, a mapping may involve a combination of two or more target vocabularies, where one or more of
them act(s) as qualifier to the other (see 8.3.4).
3.42
mapping cluster
coordinated set of mappings (3.41) between the concepts (3.17) of three or more vocabularies
NOTE See examples of mapping clusters in 6.3 and 6.4. A mapping cluster is generally maintained and published
with a particular publishing or application objective. For example, a cluster of mappings between four different thesauri
might be maintained so that the user of any one of them can easily search document collections indexed with any of the
four.
3.43
markup
annotations or other type of encoding embedded in text, in conformity with a markup language (3.44)
3.44
markup language
set of encoding conventions that can be used to provide instructions for the interpretation of a text, by the use
of annotations embedded in the text itself
NOTE The interpretation often concerns issues such as content, structure or rendering of the text. Widely used
examples include HTML (Hypertext Markup Language), which is largely concerned with presentation, and XML
(Extensible Markup Language), which addresses the structure of text.
3.45
metadata
data that identify attributes of a document (3.24) typically used to support functions such as location,
discovery, documentation, evaluation and/or selection
NOTE Preferred terms or notations selected during the indexing process are commonly applied as metadata values.
3.46
microthesaurus
designated subset of a thesaurus (3.86) that is capable of functioning as a complete thesaurus (3.86)
3.47
monohierarchical structure
hierarchical arrangement of concepts (3.17), in a thesaurus (3.86) or classification scheme (3.12), in which
each concept (3.17) can have only one broader concept (3.17) at the level immediately above
cf. polyhierarchical structure (3.58)
EXAMPLE
In a monohierarchical structure, the concept of pianos cannot be listed under keyboard instruments as well as
under stringed instruments; a choice has to be made of one of these concepts to determine its placing.

3.48
multilingual thesaurus
thesaurus (3.86) in which terms (3.84) and relational structures are available in two or more natural
languages
3.49
multi-word term
term (3.84) consisting of more than one word
cf. compound term (3.16)
EXAMPLE
cost benefit analysis
3.50
name authority list
controlled vocabulary (3.19) for use in naming particular entities consistently
NOTE The entities in question are unique individuals, such as Benjamin Disraeli, Kilimanjaro or the Bayeux Tapestry,
rather than classes such as politicians, mountains or embroideries. A name authority list may also be known as a name
authority file. In this part of ISO 25964, a name authority list is sometimes referred to simply as an authority list.
8 © ISO 2013 – All rights reserved

3.51
narrower term
preferred term (3.62) representing a concept (3.17) which is narrower than the one in question
NOTE The scope of the narrower concept falls completely within the scope of the broader. The relationship between
the two is commonly indicated with the tag NT. For more explanation see ISO 25964-1:2011, 10.2.1.
3.52
node label
label inserted into a hierarchical or classified (3.11) display to show how the terms (3.84) have been
arranged
NOTE A node label is neither a preferred term nor a non-preferred term. It contains one of two different types of
information: either a) the name of a facet to which following terms belong; or b) the attribute or characteristic of division by
which an array of sibling concepts has been sorted or grouped. See examples in ISO 25964-1:2011, Clause 11.
3.53
non-preferred term
non-descriptor
term (3.84) that is not assigned to documents (3.24) but is provided as an entry point in a thesaurus (3.86)
or index
cf. entry term (3.25)
EXAMPLE
hounds
USE dogs
NOTE A non-preferred term is followed by a reference to the appropriate preferred term or preferred terms.
3.54
notation
class code
class number
classmark
set of symbols representing a concept (3.17) or class (3.10) in a structured vocabulary (3.74), especially a
classification scheme (3.12)
EXAMPLES
Notation Source vocabulary Concept
07.04.4 ILO Thesaurus Fishery policy and development
622.342 2 Dewey Decimal Classification gold mining
373.3.016:51 Universal Decimal Classification mathematics curriculum in primary schools
SBS XEJ B Bliss Bibliographic Classification endangered species law
H40-H42 International Statistical Classification of Glaucoma
Diseases and Related Health Problems

NOTE Notation is sometimes used to sort and/or locate concepts in a pre-determined systematic order and,
optionally, to display how the components of complex concepts have been structured and grouped. A notation can provide
the link between alphabetical and systematic lists in a thesaurus. In the context of classification schemes, “concepts” are
often known as “subjects”, especially when they are complex as in the examples above.
3.55
one-to-many mapping
mapping (3.41) in which a single concept (3.17) in one vocabulary is mapped (3.39) to a combination of two
or more concepts (3.17) in another vocabulary
NOTE This situation is different from one in which a concept has two or more independent mappings to concepts in
the other vocabulary.
3.56
one-to-one mapping
mapping (3.41) in which a single concept (3.17) in one vocabulary is mapped (3.39) to a single concept
(3.17) in another vocabulary
NOTE 1 The terms or notations used to label the concepts in the two vocabularies may or may not be identical.
NOTE 2 It is possible for a single concept to have two or more one-to-one mappings, if these are independent of each
other.
3.57
ontology
a formal, explicit specification of a shared conceptualization
[31] [18]
NOTE This definition is attributable to Studer et al. , extending an earlier definition by Gruber , and is adopted in
this part of ISO 25964 because it is widely accepted in the ontology development community. An ontology typically
includes definitions of concepts and specified relationships between them, set out in a formal way so that a machine can
use them for reasoning. This definition excludes thesauri, classification schemes and other structured vocabularies
described in this part of ISO 25964, even though these are sometimes described as “lightweight ontologies”.
3.58
polyhierarchical structure
hierarchical arrangement of concepts (3.17), in a thesaurus (3.86) or classification scheme (3.12), in which
each concept (3.17) can have more than one broader concept (3.17)
cf. monohierarchical structure (3.47)
EXAMPLE
In a polyhierarchical structure, organs (musical instruments) could be listed under keyboard instruments as well
as under wind instruments.
NOTE In a polyhierarchical structure, a single concept can occur at more than one place in the hierarchical structure
of the thesaurus. Its attributes and relationships, and specifically its narrower and related terms, are the same wherever it
occurs.
3.59
post-coordination
combination of preferred terms (3.62) of a controlled vocabulary (3.19) at the time of searching
cf. pre-coordination (3.60)
EXAMPLE
The post-coordinated search expression “microwaves AND radiation” can be used to retrieve documents on
microwave radiation, when these have been indexed under the separate terms “microwaves” and “radiation”
rather than a compound term.
10 © ISO 2013 – All rights reserved

3.60
pre-coordination
combination of concepts (3.17), classes (3.10) or terms (3.84) of a controlled vocabulary (3.19) at the time
of its construction or at the time of using it for indexing (3.36) or classification (3.11)
cf. post-coordination (3.59)
EXAMPLE 1
The class “general theory”, when placed within the broader class “music”, refers only to the pre-coordinated
subject “theory of music” and not to theory in general.

EXAMPLE 2
The pre-coordinated string “cardboard — recycling” might appear in a subject heading scheme, or if not
enumerated there, it might be synthesized by an indexer when needed for a particular document.

3.61
precision
measure of retrieval performance defined by R/T, where R is the number of relevant items retrieved and T is
the total number of items retrieved from the same collection (3.13)
3.62
preferred term
descriptor
term (3.84) used to represent a concept (3.17) when indexing (3.36)
cf. non-preferred term (3.53)
NOTE A preferred term is usually a noun or noun phrase.
3.63
protocol
convention that defines the syntax, semantics and synchronization of the communication process between
two computers in order to enable a particular service
3.64
quasi-synonym
near-synonym
one of two or more terms (3.84) whose meanings are generally regarded as different in ordinary usage but
which may be treated as labels for the same concept (3.17), in a given controlled vocabulary (3.19)
EXAMPLES
diseases, disorders
earthquakes, earth tremors
3.65
recall
measure of retrieval performance defined by R/N, where R is the number of relevant items retrieved and N is
the total number of relevant items in the collection (3.13)
3.66
related term
preferred term (3.62) representing a concept (3.17) which has an associative relationship (3.2) with the
one in question
NOTE The relationship between related terms is commonly indicated with the tag RT. For more explanation, see
ISO 25964-1:2011, 10.3.
3.67
schedule
term
...