ISO/IEC 26559:2017

INTERNATIONAL ISO/IEC
STANDARD 26559
First edition
2017-07
Software and systems engineering —
Methods and tools for variability
traceability in software and systems
product line
Ingénierie des systèmes et du logiciel — Méthodes et outils pour
modéliser la traçabilité dans les gammes de produits des logiciels et
systèmes
Reference number
ISO/IEC 26559:2017(E)
©
ISO/IEC 2017

---------------------- Page: 1 ----------------------
ISO/IEC 26559:2017(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO/IEC 2017, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
Ch. de Blandonnet 8 • CP 401
CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO/IEC 2017 – All rights reserved

---------------------- Page: 2 ----------------------
ISO/IEC 26559:2017(E)

Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Abbreviated terms . 2
5 Reference model for variability traceability in software and systems product line .2
5.1 Overview . 2
5.2 Reference model for variability traceability in software and systems product line . 4
6 Variability tracing management . 7
6.1 General . 7
6.2 Variability tracing planning . 7
6.2.1 Purpose of variability tracing planning . 7
6.2.2 Design variability tracing strategy . 8
6.2.3 Define quality assurance measures for variability tracing . 8
6.2.4 Assign responsibility for variability tracing . 9
6.2.5 Record variability tracing plan . 9
6.3 Variability tracing enabling .10
6.3.1 Purpose of variability tracing enabling .10
6.3.2 Provide guidance for variability tracing .10
6.3.3 Mobilize roles and responsibilities for variability tracing .11
6.3.4 Enable variability tracing management .11
6.3.5 Enable variability tracing operations.11
6.3.6 Enable quality assurance measurement for variability tracing .12
6.4 Variability tracing managing .12
6.4.1 Purpose of variability tracing managing .12
6.4.2 Review the plan versus actual result of variability tracing .13
6.4.3 Control issues on domain/application variability tracing .13
6.4.4 Control issues on variability traceability management .13
6.4.5 Control issues on variability tracing support .14
6.4.6 Support corrective actions for variability tracing .14
6.4.7 Make improvement actions for variability tracing .15
7 Variability tracing .15
7.1 General .15
7.2 Traceability between domain variability model and domain artefacts .15
7.2.1 Purpose of traceability between domain variability model and
domain artefacts .15
7.2.2 Identify relations between variation point and domain artefact .16
7.2.3 Identify relations between variant and domain artefact .16
7.2.4 Define the trace links between domain variability model and domain artefacts .17
7.3 Traceability between application variability model and application artefacts .17
7.3.1 Purpose of traceability between application variability model and
application artefacts .17
7.3.2 Identify relations between variation point and application artefact .18
7.3.3 Identify relations between variant and application artefact .18
7.3.4 Define the trace links between application variability model and
application artefacts .19
7.4 Traceability between domain and application variability model .19
7.4.1 Purpose of traceability between domain and application variability model .19
7.4.2 Identify relations between domain and application variability model .20
7.4.3 Define trace links in accordance with binding results .20
7.5 Traceability among variability related artefacts within a stage .20
© ISO/IEC 2017 – All rights reserved iii

---------------------- Page: 3 ----------------------
ISO/IEC 26559:2017(E)

7.5.1 Purpose of traceability between variability related artefacts within a stage .20
7.5.2 Identify relations among domain artefacts within the same stage .21
7.5.3 Define trace links among domain artefacts within the same stage .21
7.5.4 Instantiate trace links in line with binding results.22
7.6 Traceability between variability related artefacts in adjacent stages .22
7.6.1 Purpose of traceability between variability related artefacts in different
adjacent stages .22
7.6.2 Identify relations between domain artefacts in adjacent stages .23
7.6.3 Define trace links between domain artefacts in adjacent stages .23
7.6.4 Instantiate trace links in line with binding results.24
8 Variability tracing support.24
8.1 General .24
8.2 Relating tracing to variability model.24
8.2.1 Purpose of relating tracing to variability model . .24
8.2.2 Identify variability tracing conflicts .25
8.2.3 Harmonize variability traceability with product line traceability .25
8.3 Quality assurance for variability tracing .26
8.3.1 Purpose of quality assurance for variability tracing .26
8.3.2 Objectively evaluate variability tracing activities .26
8.3.3 Objectively evaluate variability tracing work products .27
8.3.4 Communicate and resolve noncompliance issues.27
8.3.5 Establish records of tracing quality assurance activities .28
8.4 Variability tracing algorithm .28
8.4.1 Purpose of variability tracing algorithm .28
8.4.2 Identify algorithms for variability tracing .29
8.4.3 Evaluate defined variability tracing algorithms .29
8.4.4 Measure the performance of algorithms .30
8.4.5 Optimize traceability algorithms .30
Annex A (informative) Variability traceability dimension .31
Annex B (informative) Types of variability traceability relations .32
Annex C (informative) Variability traceability attributes.34
Bibliography .35
iv © ISO/IEC 2017 – All rights reserved

---------------------- Page: 4 ----------------------
ISO/IEC 26559:2017(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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for
the different types of document should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
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. Details of any patent rights identified during the development of the document will be in the
Introduction and/or on the ISO list of patent declarations received (see www .iso .org/ patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO’s adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: w w w . i s o .org/ iso/ foreword .html.
This document was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 7, Software and systems engineering.
© ISO/IEC 2017 – All rights reserved v

---------------------- Page: 5 ----------------------
ISO/IEC 26559:2017(E)

Introduction
Software and Systems Product Line (SSPL) engineering and management creates, exploits and manages
a common platform to develop a family of products (e.g. software products, systems architectures) at
lower cost, reduced time to market and with better quality. As a result, it has gained increasing global
attention since the 1990s.
Variability, which differentiates a member product from other products within a product line, plays an
important role in SSPL; and hundreds of variabilities are introduced throughout the whole SSPL domain
engineering stages. Those variabilities are defined, refined, newly added as domain engineering stages
go forward. Variabilities thus are modelled carefully so as to manage and control them in a systematic
way. This document deals with methods and tools capability for supporting variability modelling using
consistent notations and for managing and/or utilizing variability models in domain and application
engineering lifecycle processes.
This document can be used in the following modes:
— by the users of this document: to benefit people who want to adopt SSPL for producing their products
by guiding how to model variabilities among member products;
— by a product line organization: to provide guidance in the evaluation and selection for methods and
tools for variability modelling;
— by providers of tools and methods: to provide guidance in implementing or developing methods and
tools by providing a comprehensive set of methods and tools capabilities for supporting variability
modelling.
The ISO/IEC 26550 family of standards addresses both engineering and management processes and
capabilities of methods and tools in terms of the key characteristics of product line development. This
document provides processes and capabilities of methods and tools for variability modelling in product
lines. Other ISO/IEC 26550 family of standards are as follows:
— processes and capabilities of methods and tools for domain requirements engineering and
application requirements engineering are provided in ISO/IEC 26551;
— processes and capabilities of methods and tools for domain design and application design are
provided in ISO/IEC 26552;
— processes and capabilities of methods and tools for domain realization and application realization
are provided in ISO/IEC 26553;
— processes and capabilities of methods and tools for domain testing and application testing are
provided in ISO/IEC 26554;
— processes and capabilities of methods and tools for technical management are provided in
ISO/IEC 26555;
— processes and capabilities of methods and tools for organizational management are provided in
ISO/IEC 26556;
— processes and capabilities of methods and tools for variability mechanisms are provided in
ISO/IEC 26557;
— processes and capabilities of methods and tools for variability traceability are provided in
ISO/IEC 26559;
— processes and capabilities of methods and tools for product management are provided in
ISO/IEC 26560;
— processes and capabilities of methods and tools for technical probe are provided in ISO/IEC 26561;
vi © ISO/IEC 2017 – All rights reserved

---------------------- Page: 6 ----------------------
ISO/IEC 26559:2017(E)

— processes and capabilities of methods and tools for transition management are provided in
ISO/IEC 26562;
— processes and capabilities of methods and tools for configuration management of asset are provided
in ISO/IEC 26563;
— others (ISO/IEC 26564 to ISO/IEC 26599): to be developed.
ISO/IEC 26550, ISO/IEC 26551 and ISO/IEC 26555 are published. ISO/IEC 26557 and ISO/IEC 26559
are to be published. ISO/IEC 26552, ISO/IEC 26553, ISO/IEC 26554, ISO/IEC 26556, ISO/IEC 26560,
ISO/IEC 26561, ISO/IEC 26562, ISO/IEC 26563 are planned International Standards.
© ISO/IEC 2017 – All rights reserved vii

---------------------- Page: 7 ----------------------
INTERNATIONAL STANDARD ISO/IEC 26559:2017(E)
Software and systems engineering — Methods and tools for
variability traceability in software and systems product line
1 Scope
This document, within the context of the tools and methods of variability traceability for software and
system product lines:
— provides the terms and definitions specific to variability traceability for software and systems
product lines;
— defines process groups and their processes for establishing and managing variability traceability at
product line lifecycle processes. Those processes are described in terms of purpose, inputs, tasks,
and outcomes;
— defines method capabilities to support the defined tasks of each process;
— defines tool capabilities to automate/semi-automate tasks or defined method capabilities.
This document does not concern processes and capabilities of tools and methods for a single system but
rather deals with those for a family of products.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— IEC Electropedia: available at http:// www .electropedia .org/
— ISO Online browsing platform: available at http:// www .iso .org/ obp
3.1
aspect
special consideration within product line engineering process groups and tasks to which we can
associate specialized methods and tools
3.2
instantiated trace link
trace link (3.6) derived by applying binding in a member product
3.3
texture
architectural texture
collection of common development rules and constraints for realising the applications of a product line
3.4
traceability
discernible association among two or more logical entities, such as requirements, system elements,
verifications, or tasks
© ISO/IEC 2017 – All rights reserved 1

---------------------- Page: 8 ----------------------
ISO/IEC 26559:2017(E)

3.5
traceability with different abstraction level
level of detail for established traceability (3.4)
EXAMPLE The finer level of detail, the more general level.
3.6
trace link
association between two trace artefacts or between an element of variability model and a development
artefact
3.7
trace link semantics
purpose or meaning of the trace link (3.6), specified in the trace link types
EXAMPLE ‘Implements’, ‘refines’, ‘requires’ and ‘excludes’.
3.8
variability traceability
traceability (3.4) among variability definition, variability implementation in domain engineering and
application engineering, and thereafter tracing impacts due to variability changes
3.9
variant
instance or value of a variation point (3.10)
3.10
variation point
indication of product differentiation based on particular variable characteristics of products, domain
assets, and application assets in the context of a product line
4 Abbreviated terms
CRUD create, read, update, delete
OVM orthogonal variability model
SSPL software and systems product line
5 Reference model for variability traceability in software and systems
product line
5.1 Overview
Variability is a key differentiator between single-system engineering and management and product
line engineering and management. Product line engineering and management has to take explicitly
into account the variations within and between multiple products. The product line variabilities are
introduced and defined during product management, domain engineering and application engineering
processes defined in ISO/IEC 26550. Explicitly defined variability is represented or implemented
by different development artifacts, and it should be traced for the proper management. Variability
traceability enables tracing variabilities defined in variability models from their introduction stage to
binding stage. Variability tracing should be able to trace variability with all of relevant development
artefacts of domain engineering and application engineering processes of ISO/IEC 26550.
SSPL traceability provides a set of linkages of artefacts in a product line. Compared to the traceability
of single product development, SSPL traceability is more complex because SSPL has two separate
but intimately related development processes, i.e. domain engineering and application engineering.
SSPL traceability includes trace links between artefacts within the same stages, trace links between
2 © ISO/IEC 2017 – All rights reserved

---------------------- Page: 9 ----------------------
ISO/IEC 26559:2017(E)

artefacts produced in different stages, trace links between domain and application artefacts, and trace
links among variability-related artefacts. This document deals with trace links among variability-
related artefacts, i.e. variability traceability.
Variability traceability enables the establishment and maintenance of trace links among variabilities
described in the various forms of domain assets, application assets, and variability models.
Variability traceability is important for the consistent maintenance and evolution of variabilities
implemented/described in those various forms. Trace links can be simple relationships between
different variability-related artefacts or they can be comprehensive and sophisticated trace information
including trace link semantics. Because having too much (comprehensive) or too little (simple)
traceability is costly or insufficient, an economic analysis for the abstraction level of traceability should
be conducted in order to make decision on the appropriate level of details for traceability establishment
and management.
The variability of a product line is spread all over development artefacts, so it is difficult to trace
variability, for example, between the sources of variability and the corresponding artefacts. An
orthogonal variability model (OVM), a separated model defining the variability of a product line, provides
a cross-sectional view of the variability across all development artefacts. It relates the elements of a
variability defined to different development artefacts such as feature models, requirements artefacts,
architecture, detailed designs, codes, test artefacts, and after compile time artefacts (e.g. makefile).
Thus, the variability of different development artefacts can be traced through an OVM. Figure 1
illustrates the concept of OVM-based variability traceability in domain engineering.
Figure 1 — OVM-based variability tracing in domain engineering
Variability relating to several domain development artefacts can be traced through the OVM. As shown
in Figure 1, a variation point or variant can relate to different development artefacts of different stages.
They can relate to a use case, corresponding sub-systems, and corresponding components. Therefore,
relations among artefacts corresponding to the same variability either located in the same stage or
different stages can be traced through the links from the elements of the OVM. Because the trace links
from the OVM to development artefacts include links from a variation point to its representing artefacts
© ISO/IEC 2017 – All rights reserved 3

---------------------- Page: 10 ----------------------
ISO/IEC 26559:2017(E)

and links from the variants to their realizing artefacts, impacts on the corresponding artefacts due to
the variability changes or evolution can be completely and easily analysed.
The OVM, namely the domain variability model, relates with the application variability model in
accordance with binding decisions and the corresponding trace links are also instantiated along with
binding. Member product specific variability is defined through the application variability model and
it relates to the corresponding application artefacts. From introduction time through binding time,
variability traceability is achieved through the instantiated trace links, trace links between the OVM
and application variability model, and member product specifically established trace links. Figure 2
illustrates OVM based variability tracing in a product line.
Domain artefact Application artefact
Figure 2 — OVM based variability tracing within a product line
The thick broken line means instantiated trace links in accordance with binding decisions in application
engineering. There exists a newly added variability (e.g. CfgDisplay in Figure 2) and its trace link with
application artefacts is defined.
5.2 Reference model for variability traceability in software and systems product line
The reference model specifies the structure of supporting processes and subprocesses for variability
traceability in product line. As shown in Figure 3, variability traceability in product line can be
structured into three processes: variability tracing management, variability tracing and variability
tracing support. In the rest of this document, tasks, methods and tools are described in terms of
processes and subprocesses defined in the reference model.
Each process is divided into subprocesses and each subprocess is described in terms of the following
attributes:
— the title of the subprocess;
— the purpose of the subprocess;
4 © ISO/IEC 2017 – All rights reserved

---------------------- Page: 11 ----------------------
ISO/IEC 26559:2017(E)

— the inputs to produce the outcomes;
— the tasks to achieve the outcomes;
— the outcomes of the subprocess;
— the capabilities of tools and methods are a list of the required support of tools and methods for
performing the tasks properly.
Figure 3 — Variability traceability in SSPL
The variability tracing management process supports for establishing plans for establishing
and maintaining variability traceability with the different levels of detail, for providing enabling
environments for realizing the planned variability traceability, and for managing plans versus actual
variability traceabili
...