ISO/IEC Guide 77-2:2008
(Main)Guide for specification of product properties and classes — Part 2: Technical principles and guidance
Guide for specification of product properties and classes — Part 2: Technical principles and guidance
ISO/IEC Guide 77 provides general advice and guidance for the description of products and their characteristics by the use of the ISO 13584 and IEC 61360 series of standards for the creation of computer-processable reference dictionaries. This description will provide the details of the products and their properties in an unambiguous manner capable of computer communication, in a form that is independent from any proprietary application software. ISO/IEC Guide 77 is intended to assist the objective of enabling the flow of technical information between internal and external business partners in a cost-effective and timely manner. The guidance given in ISO/IEC Guide 77-2:2008 contains technical recommendations intended to assist standardization committees and technical experts contributing their knowledge to the development of standard reference dictionaries compliant with the common ISO 13584/IEC 61360 dictionary model. It might also be useful for information experts responsible for the exchange of technical information between business partners or for the generation of applications of ISO 13584 and IEC 61360. ISO/IEC Guide 77-2:2008 is intended to support the achievement of industrial benefits of applications of the common ISO 13584/IEC 61360 dictionary model. The following are within the scope of ISO/IEC Guide 77-2:2008: general principles of product description and characterization; presentation of the concepts of product characterization classes, product properties, product ontology and reference dictionaries for products; universal identification of classes and properties; presentation of the modelling constructs that can be used for building reference dictionaries conforming to the common ISO 13584/IEC 61360 dictionary model; rules and principles for developing standard reference dictionaries; rules and principles for connecting standard reference dictionaries to avoid duplication and overlap; rules and principles for developing user-defined reference dictionaries and for connecting user-defined reference dictionaries to standard reference dictionaries; formats and mechanisms for exchanging reference dictionaries; mechanisms for connecting reference dictionaries to classification systems. The following are outside the scope of ISO/IEC Guide 77-2:2008: an overview for ISO and IEC Technical Committees and industrial managers for the development of computer-processable product libraries, reference dictionaries and catalogues; case studies from experiences in the creation of reference dictionaries of product information in industrial practice; categorization of products for purposes other than product characterization.
Guide pour la spécification des classes et des propriétés du produit — Partie 2: Principes techniques et directives
General Information
Standards Content (Sample)
GUIDE 77-2
Guide for specification of
product properties and classes
Part 2:
Technical principles and
guidance
First edition 2008
©
ISO/IEC 2008
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ISO/IEC GUIDE 77-2:2008(E)
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ISO/IEC GUIDE 77-2:2008(E)
Contents Page
Foreword .iv
Introduction.v
1 Scope.1
2 Terms and definitions .2
3 General principles .7
3.1 The common ISO 13584/IEC 61360 dictionary model.7
3.2 Simultaneous description of product characterization classes and product properties.9
3.3 Attribute and relationship-based definitions.12
3.4 Universal identification of classes and properties .12
3.5 Modularity .14
4 Specifying properties.17
4.1 Properties to be defined .17
4.2 Properties and associated attributes .17
4.3 Properties and associated values .19
4.4 Properties and context of evaluation .20
4.5 Product assemblies and their properties .21
4.6 Properties and features .23
5 Designing product characterization class hierarchies.24
5.1 Product characterization classes to be defined.24
5.2 Product characterization classes and associated attributes.25
5.3 Connecting classes and properties: visibility and applicability of properties .25
5.4 Double inheritance mechanism for properties.27
5.5 Class selectors .28
5.6 Product characterization versus product categorization.28
5.7 Product characterization and engineering models.29
6 Exchanging reference dictionaries.30
Bibliography.31
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ISO/IEC GUIDE 77-2:2008(E)
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.
Draft Guides adopted by the responsible Committee or Group are circulated to the member bodies for voting.
Publication as a Guide 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/IEC Guide 77-2 was prepared by the Joint Technical Advisory Group of the ISO Technical Management
Board and the IEC Standardization Management Board on product properties and families.
ISO/IEC Guide 77 consists of the following parts, under the general title Guide for specification of product
properties and classes:
⎯ Part 1: Fundamental benefits
⎯ Part 2: Technical principles and guidance
⎯ Part 3: Experience gained
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ISO/IEC GUIDE 77-2:2008(E)
Introduction
The capability to characterize products in an abstract way, independently of any particular manufacturer, is a
fundamental aspect of engineering knowledge. Such a characterization is done by the name of a category of
products that fulfils the same function, e.g. ball bearing, screw, capacitor. Such a category is called a
characterization class. This first level of characterization is further detailed by means of some property-value
pairs, which describe more precisely the target product within its characterization class. Examples of such
properties are inner diameter, threaded length and capacitance.
Depending upon the context, products need to be characterized at various levels of accuracy. For example, in
a preliminary engineering design phase, the need for a bearing with a particular inner diameter could be
defined, with other properties of the bearing left unspecified. At a latter stage, it could be decided to use a ball
bearing with a particular outside diameter and ball diameter; finally, a thrust angular contact ball bearing could
be selected with contact angle equal to 80.
Consequently, characterization classes need to be defined at various levels of generality. A specialized class
makes it possible to refine a requirement described in terms of a more general class. This
generalization/specialization relationship between characterization classes builds up a hierarchy of
characterization classes where each general class is refined into more specialized classes. The most
specialized classes, called the leaf classes, are at the bottom of the hierarchy. In such a hierarchy, each class
is associated with properties that can be used to characterize all the products belonging to this class. Note
that a ball bearing being a bearing, all the properties applying to a bearing also apply to a ball bearing.
Properties defined for more general classes can therefore also be used for all their specialized classes.
Applicability of properties to classes is said to be inherited over the hierarchy.
Neither product characterization classes nor product properties are single words. They are concepts that
belong to the engineering knowledge of specific engineering domains. These concepts exist independently of
any particular language, and they can be referenced in various languages and technical jargons using various
words. Usual word dictionaries are therefore inappropriate for describing such multilingual knowledge and for
making it computer interpretable.
The goal of ISO/IEC Guide 77 is to describe how this knowledge can be modelled in a language-independent
and computer interpretable way.
For each technical domain, the target result essentially consists of:
⎯ a hierarchy (or a set of hierarchies) of characterization classes, each associated with a language-
independent identifier and with a number of information elements, called attributes, that describe the
corresponding concept, and
⎯ a set of properties, each associated with a characterization class, that are inherited over the class
hierarchy, and that have also language-independent identifier and descriptive attributes (name in various
languages, domain of allowed values, etc.).
Such a structure is called a product ontology (see 2.17), to emphasize that it is a knowledge model that
defines concepts and not words. In ISO/IEC Guide 77, each particular product ontology addressing a
particular product domain that is designed in compliance with the common ISO 13584/IEC 61360 dictionary
model for product ontology is called a reference dictionary (see 2.20) for that domain, keeping in mind that it
is not a dictionary of words but a dictionary of concepts.
When an attempt is made to design or to use a reference dictionary for a particular domain (e.g. fasteners), a
number of issues appear, notably including the following:
⎯ which data to use for modelling characterization classes and product properties;
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⎯ how to represent characterization class hierarchies and relationships between classes and properties;
⎯ how to avoid redefining properties that are already defined in other reference dictionaries;
⎯ how to avoid a combinatorial blow-up when one tries to describe all the various categories of, for
example, bolts and screws;
⎯ how to extract from a standard reference dictionary only those properties that are useful for a particular
company.
To answer these questions, a common information model for product ontologies, called the common
ISO 13584/IEC 61360 dictionary model (see 2.6), has been developed as a joint effort of ISO/TC 184,
Automation systems and integration, SC 4, Industrial data, WG 2, Standard for the neutral representation of
standard parts, and of IEC/TC 3, Information structures, documentation and graphical symbols, SC 3D, Data
sets for libraries.
This model has been defined in a formal data modelling language called EXPRESS. Thus, a number of
software tools have been developed that support all the concepts of this model. These tools can be used by
domain experts for building their own reference dictionaries without any knowledge about EXPRESS, while
ensuring that the data representation of these reference dictionaries will be exchangeable in a standard way.
The only prerequisite is to understand the concepts and mechanisms defined in the model: this part of
ISO/IEC Guide 77 aims to provide this background.
Due to the diversity of industrial sectors and of engineering disciplines, creating reference dictionaries that
cover the whole technical domain is a huge task that can only be performed by a number of parallel groups
and projects. To ensure interoperability of the developed reference dictionaries, it is crucial that the same data
model be used. It is also crucial that some mechanisms be used to connect the various reference dictionaries
and to reuse in each reference dictionary the relevant properties that are already defined in some other
reference dictionary. For these reasons, the ISO Technical Management Board and the IEC Standards
Management Board decided to establish ISO/IEC/JWG 1. Its role has been to produce a guide for
specification of product properties and families on the basis of the common ISO 13584/IEC 61360 dictionary
model, and to produce recommendations and guidelines on how to monitor consistency of the work items
produced in accordance with the guide across all ISO/IEC Technical Committees. These guidelines are
documented in this multi-part ISO/IEC Guide 77. ISO/IEC Guide 77 is not only of interest to ISO and IEC
Technical Committees for developing standard reference dictionaries, it can also be useful to any group,
consortium or industrial organization that needs to develop interoperable reference dictionaries.
Developing reference dictionaries is a design task. It is based on a number of design choices and decisions
that need to be agreed upon in a consensual way to ensure acceptability of the developed reference
dictionary. These choices are largely domain-dependent, therefore no universal and systematic methodology
can be built. To help domain experts in the process, ISO/IEC Guide 77-3 provides some reports of previous
experience in the use of the common ISO 13584/IEC 61360 dictionary model in reference dictionary design.
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ISO/IEC GUIDE 77-2:2008(E)
Guide for specification of product properties and classes
Part 2:
Technical principles and guidance
1 Scope
ISO/IEC Guide 77 provides general advice and guidance for the description of products and their
characteristics by the use of the ISO 13584 and IEC 61360 series of standards for the creation of computer-
processable reference dictionaries. This description will provide the details of the products and their properties
in an unambiguous manner capable of computer communication, in a form that is independent from any
proprietary application software.
NOTE 1 The term “product” is taken to include devices, processes, systems, installations, etc.
ISO/IEC Guide 77 is intended to assist the objective of enabling the flow of technical information between
internal and external business partners in a cost-effective and timely manner.
The guidance given in this part of ISO/IEC Guide 77 contains technical recommendations intended to assist
standardization committees and technical experts contributing their knowledge to the development of standard
reference dictionaries compliant with the common ISO 13584/IEC 61360 dictionary model.
It might also be useful for information experts responsible for the exchange of technical information between
business partners or for the generation of applications of ISO 13584 and IEC 61360.
This part of ISO/IEC Guide 77 is intended to support the achievement of industrial benefits of applications of
the common ISO 13584/IEC 61360 dictionary model. The following are within the scope of this part of
ISO/IEC Guide 77:
⎯ general principles of product description and characterization;
⎯ presentation of the concepts of product characterization classes, product properties, product ontology and
reference dictionaries for products;
⎯ universal identification of classes and properties;
⎯ presentation of the modelling constructs that can be used for building reference dictionaries conforming to
the common ISO 13584/IEC 61360 dictionary model;
⎯ rules and principles for developing standard reference dictionaries;
⎯ rules and principles for connecting standard reference dictionaries to avoid duplication and overlap;
⎯ rules and principles for developing user-defined reference dictionaries and for connecting user-defined
reference dictionaries to standard reference dictionaries;
⎯ formats and mechanisms for exchanging reference dictionaries;
⎯ mechanisms for connecting reference dictionaries to classification systems.
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ISO/IEC GUIDE 77-2:2008(E)
The following are outside the scope of this part of ISO/IEC Guide 77:
⎯ an overview for ISO and IEC Technical Committees and industrial managers for the development of
computer-processable product libraries, reference dictionaries and catalogues;
NOTE 2 An overview of the development of computer-processable product libraries, reference dictionaries and
catalogues is provided in ISO/IEC Guide 77-1.
⎯ case studies from experiences in the creation of reference dictionaries of product information in industrial
practice;
NOTE 3 Experience gained in the creation of reference dictionaries of product information in industrial practice is
provided in ISO/IEC Guide 77-3.
⎯ categorization of products for purposes other than product characterization.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
applicable property of a class
property relevant for any product belonging to a product characterization class and that can be used for
characterizing it
NOTE 1 All the applicable properties of a superclass are also applicable properties for its subclasses.
NOTE 2 Only properties defined or inherited as visible and imported properties of a class can become applicable
properties.
2.2
attribute
data element for the computer-sensible description of a property, a relation or a class
NOTE An attribute describes only one single detail of a property, of a class or of a relation.
EXAMPLE The name of a property, the code of a class, the measure unit in which values of a property are provided
are examples of attributes.
2.3
class
class of products
abstraction of a set of similar products
NOTE 1 A product that complies with the abstraction defined by a class is called a class member (see 2.5).
NOTE 2 A class is an intentional concept that can take different extensional meanings in different contexts.
EXAMPLE The set of parts used by a particular enterprise and the set of all ISO-standardized parts are two
examples of contexts. In these two contexts, the set of products that are considered as members of the single ball bearing
class might be different, notably because employees of each enterprise ignore a number of existing single ball bearing
products.
NOTE 3 Classes are structured by class inclusion relationships.
NOTE 4 A class of product is a general concept as defined in ISO 1087-1. It is therefore advisable that the rule defined
in ISO 704 be used for defining the designation and definition attributes of classes of product.
NOTE 5 In the context of this part of ISO/IEC Guide 77, a class is either a product characterization class, associated
with properties and usable for characterizing products, or a product categorization class, not associated with properties
and not usable for characterizing products.
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2.4
class inclusion relationship
relationship between classes that means inclusion of class members
NOTE 1 Therefore, if A is a superclass of A1, this means that, in any context, any member of A1 is also member of A.
EXAMPLE 1 The set of parts used by a particular enterprise and the set of all ISO-standardized parts are two
examples of contexts.
EXAMPLE 2 In any context, the class capacitor includes the class electrolytic capacitor.
NOTE 2 Class inclusion defines a hierarchical structure between classes.
NOTE 3 Class inclusion is a conceptual relationship that does not prescribe anything at the data representation level;
consequently, it does not prescribe any particular database schema or data model.
NOTE 4 In the common ISO 13584/IEC 61360 dictionary model, the is-a relationship (see 2.9) ensures class
inclusion. This part of ISO/IEC Guide 77 also recommends that the case-of (see 2.10) relationship also ensure class
inclusion.
NOTE 5 Class inclusion relationship is a case of generic relation as defined in ISO 1087-1.
NOTE 6 Class inclusion relationship is also called subsumption.
2.5
class member
product that complies with the abstraction defined by a class
2.6
common ISO 13584/IEC 61360 dictionary model
data model for product ontology, using the information modelling language EXPRESS, resulting from a joint
effort between ISO/TC 184/SC 4/WG 2 and IEC/SC 3D
NOTE 1 In ISO/IEC Guide 77, a product ontology that addresses a particular product domain, based on the common
ISO 13584/IEC 61360 dictionary model, is called a reference dictionary (see 2.20) for that domain.
NOTE 2 The current version of the common ISO 13584/IEC 61360 dictionary model recommended by
ISO/IEC Guide 77 is documented in EXPRESS in both IEC 61360-5 and ISO 13584-25 (conformance classes 1,2, 3 and
4). It is also documented in UML, together with its XML exchange format, in ISO 13584-32, OntoML.
NOTE 3 The common ISO 13584/IEC 61360 dictionary model is used in a number of ISO and IEC standards, including
IEC 61360-4-DB, ISO 13584-501, ISO 13399, ISO 13584-511, ISO 23584, IEC 61987-2, ISO/TS 23768.
2.7
feature
aspect of a product that can be described by a characterization class and a set of property-value pairs
NOTE In the common ISO 13584/IEC 61360 dictionary model, features and products are both represented by
product characterization classes. The concept of feature is only a useful design concept to be considered when designing
the class hierarchy and the associated properties of a reference dictionary.
EXAMPLE Screws can be described as consisting of different features, such as screw head, screw thread, screw
shank, and screw end. Such a description, used in ISO 13584-511:2006, makes it possible to describe a huge number of
different screws by a smaller number of screw classes that reference a small number of feature classes.
2.8
imported property
property defined in a class that is selected by another class of the same or of a different reference dictionary,
by means of the case-of relationship, to become applicable to the latter class
NOTE 1 Only properties that are visible and/or applicable in a class can be imported from this class.
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NOTE 2 Importation between classes of different reference dictionaries enables properties, e.g. properties defined for
example in a standard reference dictionary, to be reused without having to be redefined.
NOTE 3 Importation between classes of the same reference dictionary acknowledges the fact that some products can
perform several functions, requiring the capability to import properties from several higher level classes.
NOTE 4 When a property is imported in a new class, it keeps its original identifier; consequently, it is not necessary to
duplicate all the attributes.
2.9
is-a relationship
class inclusion relationship associated with inheritance
NOTE 1 Therefore, if A1 is-a A, then each product belonging to A1 belongs to A, and all class properties described in
the context of A are also automatically described in the context of A1.
NOTE 2 This mechanism is usually called inheritance.
NOTE 3 In the common ISO 13584/IEC 61360 dictionary model, the is-a relationship can only be defined between
characterization classes. It is advisable that it defines a single hierarchy, and it ensures that both visible and applicable
properties are inherited.
2.10
is-case-of relationship
case-of
property importation mechanism
NOTE 1 Therefore, if A1 is-case-of A, then the definition of A products also covers A1 products, thus A1 can import any
property from A.
NOTE 2 The goal of the is-case-of relationship is to allow the connecting together of several class inclusion
hierarchies, while ensuring that referenced hierarchies may be updated independently.
NOTE 3 There is no constraint that the is-case-of relationship define a single hierarchy.
NOTE 4 In the common ISO 13584/IEC 61360 dictionary model, the is-case-of relationship can notably be used in four
cases:
a) to link a characterization class to a product characterization,
b) to import, in the context of some standardized reference dictionaries some properties already defined in other
standardized reference dictionaries,
c) to connect a user reference dictionary to one or several standardized reference dictionaries, and
d) to describe a part using the properties of different classes.
When parts of class A1 fulfil two different functions, and thus are logically described by properties associated with two
different classes, A and B, A1 can be connected by is-a to A, and by is-case-of to B.
2.11
leaf characterization class
leaf class
characterization class that is not further subdivided into more precise characterization classes
EXAMPLE Countersunk flat head screw with cross recess (type Y) and hexagon socket head cap screw with metric
fine pitch thread are leaf characterization classes defined in ISO 13584-511.
NOTE A characterization class that is further subdivided into more precise characterization classes is called a “non-
leaf characterization class” (e.g. externally-threaded component and metric threaded bolt/screw are non-leaf
characterization classes defined in ISO 13584-511).
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2.12
product
thing or substance produced by a natural or artificial process
NOTE In ISO/IEC Guide 77, the term “product” is taken in its broadest sense to include devices, systems and
installations, as well as material, software and services.
2.13
product categorization
recursive partition of a collection of products into subsets for a specific purpose
NOTE 1 Subsets which appear in a product categorization are called product categorization classes, or product
categories (see 2.14).
NOTE 2 A product categorization is not a product ontology. It cannot be used for characterizing products.
NOTE 3 No property is associated with categorizations.
NOTE 4 Several categorizations of the same set of parts are possible, depending on their target usage.
EXAMPLE The United Nations Standard Products and Services Code (UNSPSC) classification, defined by the
United Nations, is an example of product categorization that has been developed for spend analysis.
NOTE 5 Using the is-case-of relationship, several product characterization class hierarchies can be connected to a
categorization hierarchy to generate a single structure.
2.14
product categorization class
product category
class of products that constitutes an element of a classification
EXAMPLE Manufacturing Components and Supplies, and Industrial Optics are examples of product categories
defined in the UNSPSC.
NOTE 1 No rule is given in this part of ISO/IEC Guide 77 about how to select categorization classes. This concept is
introduced both to clarify its difference from characterization class, and to explain that the same characterization class can
be connected to any number of categorizations.
NOTE 2 There is no property associated with a product category.
2.15
product characterization
description of a product by means of a product characterization class, to which it belongs, and a set of
property value pairs
EXAMPLE Hexagon_head_bolts_ISO_4014 (product grades = A, thread type = M, length = 50, diameter = 8) is an
example of product characterization.
NOTE In the above example, Hexagon_head_bolts_ISO_4014 stands for the identifier of the Hexagon head bolts
product characterization class defined by ISO 4014. The names in italics between parentheses stand for the bolt
properties defined in ISO 4014.
2.16
product characterization class
class of products that fulfil the same function and that share common properties
NOTE Product characterization classes can be defined at various levels of details, thus defining a class inclusion
hierarchy.
EXAMPLE Metric threaded bolt/screw and hexagon head bolt are examples of product characterization classes
defined in ISO 13584-511. The first characterization class is included in the second one. Transistor and bipolar power
© ISO/IEC 2008 – All rights res
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