ISO/IEC 26580:2021

INTERNATIONAL ISO/IEC
STANDARD 26580
First edition
2021-04
Software and systems engineering —
Methods and tools for the feature-
based approach to software and
systems product line engineering
Ingénierie du logiciel et des systèmes — Méthodes et outils pour
l'approche basée sur les caractéristiques dans l'ingénierie de lignes de
produits logiciels et systèmes
Reference number
©
ISO/IEC 2021
© ISO/IEC 2021
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ii © ISO/IEC 2021 – All rights reserved

Contents Page
Foreword .vi
Introduction .vii
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Overview of feature-based product line engineering . 4
4.1 General . 4
4.2 Shared assets . 5
4.3 Features . 6
4.4 Automated means of production . 7
5 A feature-based specialization of software and systems product line engineering .7
6 Reference model for the feature-based approach to software and systems product
line engineering .11
6.1 General .11
6.2 Key elements of the feature-based PLE factory .12
6.2.1 General.12
6.2.2 Feature catalogue .13
6.2.3 Bill-of-features and bill-of-features portfolio .13
6.2.4 Shared asset supersets .14
6.2.5 PLE factory configurator .14
6.2.6 Product asset instances . .14
6.3 Relationships among the key elements of the factory .15
6.3.1 General.15
6.3.2 Feature-based abstractions: feature catalogue and bill-of-features portfolio .15
6.3.3 Domain supersets: feature catalogue and shared asset supersets .16
6.3.4 Assets: shared asset supersets and product asset instances .17
6.3.5 Product instances: bill-of-features portfolio and product asset instances .18
6.4 Reference model layers .19
6.5 Feature language .20
6.6 Support for a hierarchical product line of product lines .20
6.7 Other concerns .21
6.7.1 General.21
6.7.2 Configuration management concern .21
6.7.3 Traceability concern .21
6.7.4 Change management concern .22
6.7.5 Access control concern .22
7 Technology layer .22
7.1 General .22
7.2 Feature language .22
7.3 Feature catalogue .25
7.4 Bill-of-features portfolio .25
7.5 Shared asset supersets .25
7.6 Product asset instances .26
7.7 PLE factory configurator.26
7.8 PLE factory development environment .26
8 Technical organization management layer .27
8.1 General .27
8.2 Relationship to ISO/IEC 26550 technical management process group and ISO/IEC
26556 .28
8.3 Feature catalogue engineering .29
8.3.1 Purpose .29
© ISO/IEC 2021 – All rights reserved iii

8.3.2 Role .29
8.3.3 Outcomes .29
8.3.4 Inputs .29
8.3.5 Tasks .29
8.3.6 Tools .30
8.4 Bill-of-features portfolio engineering .31
8.4.1 Purpose .31
8.4.2 Role .31
8.4.3 Outcomes .31
8.4.4 Inputs .31
8.4.5 Tasks .31
8.4.6 Tools .32
8.5 Shared asset superset engineering .32
8.5.1 Purpose .32
8.5.2 Role .33
8.5.3 Outcomes .33
8.5.4 Inputs .33
8.5.5 Tasks .33
8.5.6 Tools .34
8.6 Automated configuration of the product asset instances .35
8.6.1 Purpose .35
8.6.2 Role .35
8.6.3 Outcomes .35
8.6.4 Inputs .35
8.6.5 Task — Configure the shared asset supersets using the PLE factory
configurator.35
8.6.6 Tools .35
8.7 Verification, validation, and product delivery of the product asset instances .35
8.7.1 Purpose .35
8.7.2 Role .36
8.7.3 Outcomes .36
8.7.4 Inputs .36
8.7.5 Tasks .36
8.7.6 Tools .36
8.8 Configuration management .37
8.8.1 Purpose .37
8.8.2 Role .37
8.8.3 Outcomes .37
8.8.4 Inputs .37
8.8.5 Tasks .37
8.8.6 Tools .38
8.9 Traceability management .38
8.9.1 Purpose .38
8.9.2 Role .38
8.9.3 Outcomes .38
8.9.4 Inputs .39
8.9.5 Tasks .39
8.9.6 Tools .39
8.10 Change management .40
8.10.1 Purpose .40
8.10.2 Role .40
8.10.3 Outcomes .40
8.10.4 Inputs .40
8.10.5 Tasks .40
8.10.6 Tools .41
9 Business organization management layer .41
9.1 General .41
9.2 Incorporation of ISO/IEC 26550, ISO/IEC 26556 and ISO/IEC 26562 processes .42
iv © ISO/IEC 2021 – All rights reserved

9.3 Fund the PLE factory .44
9.3.1 Purpose .44
9.3.2 Outcomes .44
9.3.3 Inputs .44
9.3.4 Task — Establish and execute a funding policy for the PLE factory .44
9.3.5 Tools .45
Annex A (informative) Terminology specialization from ISO/IEC 26550 to this document .46
Annex B (informative) UML 2.0 Diagrams for the feature-based PLE factory .50
Bibliography .51
© ISO/IEC 2021 – All rights reserved v

Foreword
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The procedures used to develop this document and those intended for its further maintenance are
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_experts/ refdocs).
Attention is drawn to the possibility that some of the elements of this document may be the subject
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This document was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 7, Software and systems engineering.
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complete listing of these bodies can be found at www .iso .org/ members .html and www .iec .ch/ national
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vi © ISO/IEC 2021 – All rights reserved

Introduction
Feature-based software and systems product line engineering (“feature-based PLE” for short) is
a specialization of software and systems product line (SSPL) engineering and management that is
described in ISO/IEC 26550. ISO/IEC 26550 describes a very generalized approach to SSPL, focusing on
the benefits of exploiting a common platform of reusable assets for a product family. Each organization
that adopts SSPL under ISO/IEC 26550 is free to do so using their preferred techniques and methods.
What is the motivation for creating a standard for a specialization of SSPL? As the SSPL field has
matured and achieved widespread attention in the industry, a specific and repeatable approach to SSPL
has emerged that takes advantage of commercial off-the-shelf industrial-strength tools and technology,
along with robust best practices for methods and processes, that automate and formalize many of the
processes in domain and application engineering. The result is that less upfront analysis, design, and
implementation effort is required prior to gaining the benefits from the approach.
While SSPL in general provides significant benefits, it also requires a significant investment of time and
effort to adopt and to ultimately achieve those benefits. The feature-based PLE specialization is a more
narrowly defined solution that can be supported by off-the-shelf tools and methods, which has resulted
in lower investments when an organization adopts SSPL. Feature-based PLE embodies lessons learned
about SSPL practices that have been shown to provide some of the highest benefits and returns (see, for
example, References [2] and[8]).
This document provides a reference model consisting of an abstract representation of the key technical
elements, tools, and methods of feature-based PLE. The predominant specializations of general SSPL
that characterize feature-based PLE are:
a) a mapping from features to asset variation points that is sufficient to drive a fully automated
configurator that produces assets specific to member products;
b) a methodological shift of all design and implementation effort, change management, and
configuration management to domain engineering, so that application engineering is reduced to
automated configuration of member product instances and testing of configured member products
and member-product-specific assets.
This document embodies a distinct separation of concerns between the feature-based PLE technology
providers and feature-based technology users. For each of these stakeholder concerns, the scope of this
document is to define only what is necessary and sufficient to enable feature-based PLE practice. For
technology providers, this imparts flexibility in how the necessary and sufficient technical capabilities
are provided, as well as the opportunity to offer more expansive capabilities that are possible in an
ideal solution. For technology users, this provides flexibility to select among the technology providers
and to apply the methods that best match their technical and business objectives for feature-based PLE.
© ISO/IEC 2021 – All rights reserved vii

INTERNATIONAL STANDARD ISO/IEC 26580:2021(E)
Software and systems engineering — Methods and tools
for the feature-based approach to software and systems
product line engineering
1 Scope
This document is a specialization of the more general reference model for software and systems
product line engineering and management described in ISO/IEC 26550. The specialization defined
herein addresses a class of methods and tools referred to as feature-based software and systems
product line engineering, or feature-based PLE, which has emerged as a proven and repeatable product
line engineering and management (PLE) practice supported by commercial tool providers.
This document:
— provides the terms and definitions specific to feature-based PLE;
— defines how feature-based PLE is a specialization within the general ISO/IEC 26550 reference model
for product line engineering and management;
— defines a reference model for the overall structure and processes of feature-based PLE and describes
how the elements of the reference model fit together;
— defines interrelationships and methods for applying the elements and tools of the product line
reference model;
— defines required and supporting tool capabilities.
In this document, products of feature-based PLE include digital work products that support the
engineering of a system. Some of the artefacts are actually part of the delivered products, while other
artefacts can be non-deliverable, such as physical or digital design models.
The intended audience for this document comprises:
— technology providers who wish to provide automated tool support for the reference model and
processes described in this document;
— champions within an organization who wish to introduce feature-based PLE throughout that
organization;
— IT staff within a PLE organization who will introduce and maintain the necessary technology to
support feature-based PLE;
— practitioner stakeholders who will use the provided technology to practice feature-based PLE;
— technical and business managers who will sponsor and direct the methods necessary to practice
feature-based PLE;
— university professors, researchers, corporate trainers, and other educators who will create and
share pedagogical materials about feature-based PLE and its benefits.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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/IEC 2021 – All rights reserved 1

ISO/IEC/IEEE 12207, Systems and software engineering — Software life cycle processes
ISO/IEC/IEEE 15288, Systems and software engineering — System life cycle processes
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC/IEEE 12207,
ISO/IEC/IEEE 15288, and the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
NOTE 1 For additional terms and definitions in the field of systems and software engineering, see
ISO/IEC/IEEE 24765, which is published periodically as a “snapshot” of the SEVOCAB (Systems and software
engineering – Vocabulary) database and is publicly accessible at www .computer .org/ sevocab.
NOTE 2 Because feature-based PLE is a specialization of the more general product line engineering approach
described in ISO/IEC 26550, some of the terminology used herein is noted as a specialization of the terminology
from ISO/IEC 26550, with further details provided in Annex A.
3.1
bill-of-features
specification for a member product (3.8) in the product line (3.16), rendered in terms of the specific
features (3.4) from the feature catalogue (3.5) that are chosen for that member product
3.2
bill-of-features portfolio
collection comprising the bill-of-features (3.1) for each member product (3.8) in a product line (3.16)
3.3
domain supersets
collection comprising the feature catalogue (3.5) and shared asset supersets (3.18)
3.4
feature
characteristic of a member product (3.8) in a product line (3.16) that distinguishes it from other member
products in the product line
Note 1 to entry: Features can a) express the customer-visible or end-user-visible variability among the member
products in a product line, or b) distinguish implementation variability not directly visible to a customer or end
user except through non-functional differences such as price, performance, noise, weight, energy and more.
Note 2 to entry: In feature-based PLE, features express differences among member products. A capability or
other characteristic common to all member products in the product line is not modelled as a feature.
Note 3 to entry: See Annex A for the definition of this term in ISO/IEC 26550.
3.5
feature catalogue
model of the collection of all the feature (3.4) options and feature constraints (3.6) available across the
entire product line (3.16)
3.6
feature constraint
formal relationship between two or more features (3.4) that is necessarily satisfied for all member
products (3.8)
2 © ISO/IEC 2021 – All rights reserved

3.7
feature language
syntax and semantics for the formal representation, structural taxonomy, and relationships among the
concepts and constructs in the feature catalogue (3.5), bill-of-features portfolio (3.2), and shared asset
superset (3.18) variation points (3.20)
3.8
member product
product belonging to the product line (3.16)
[SOURCE: ISO/IEC 26550:2015, 3.15, modified — The preferred term "application" has been removed.]
3.9
mutually exclusive
alternatives from which at most one is selected
3.10
mutually inclusive
alternatives from which zero or more are selected
3.11
PLE factory
technological, organizational, and business infrastructure and processes to support a PLE factory
configurator (3.12) producing product asset instances (3.14) from shared asset supersets (3.18) based on
a bill-of-features (3.1) for a member product (3.8)
3.12
PLE factory configurator
automated mechanism that produces assets for a specific member product (3.8) by processing the bill-
of-features (3.1) for that member product, and exercising the shared assets’ (3.17) variation points (3.20)
in light of the feature (3.4) selections made in that bill-of-features
3.13
PLE factory development environment
toolset for creating, organizing, assembling, and maintaining a collection of elements in a feature
catalogue (3.5), bill-of-features portfolio (3.2), shared asset supersets (3.18), and a hierarchy of a product
line (3.16) of product lines
3.14
product asset instance
instantiation of a shared asset (3.17) specific to a member product (3.8), automatically produced by the
PLE factory configurator (3.12), corresponding to a bill-of-features (3.1) for that member product
Note 1 to entry: A product asset instance is analogous to an application asset (ISO/IEC 26550) with the proviso
that it is produced by the PLE factory configurator.
3.15
product instances
collection comprising the bill-of-features portfolio (3.2) and product asset instances (3.14)
3.16
product line
family of similar products with variations in features (3.4)
Note 1 to entry: See Annex A for the definition of this term in ISO/IEC 26550.
3.17
shared asset
software and systems engineering lifecycle digital artefacts that compose a part of a delivered member
product (3.8) or support the engineering process to create and maintain a member product
Note 1 to entry: A shared asset is analogous to a domain asset (ISO/IEC 26550).
© ISO/IEC 2021 – All rights reserved 3

Note 2 to entry: Typical shared assets are requirements, design specifications or models for mechanical, electrical,
and software, source code, build files or scripts, test plans and test cases, user documentation, repair manuals
and installation guides, project budgets, schedules, and work plans, product calibration and configuration files,
mechanical bills-of-materials, electrical circuit board and wiring harness designs, engineering management
plans, engineering drawings, training plans and training materials, skill set requirements, manufacturing plans
and instructions, and shipping manifests.
3.18
shared asset superset
representation of a shared asset (3.17) that includes all content needed by any of the member products (3.8)
3.19
variant
alternative that can be used to realize a particular variation point (3.20)
[SOURCE: ISO/IEC 26550:2015, 3.28, modified — the word "one" at the beginning of the definition has
been removed; "may" has been changed to "can"; "particular variation points" has been changed to "a
particular variation point"; note 1 to entry has been removed.]
3.20
variation point
identification of a specific piece of shared asset superset (3.18) content and a mapping from feature (3.4)
selection(s) to the form of that content that appears in a product asset instance (3.14)
Note 1 to entry: In this document, all features express characteristics that differ among member products (3.8),
which according to ISO/IEC 26550 would also make every feature a variation point. To avoid this redundancy,
this document does not call out features as variation points.
Note 2 to entry: See Annex A for the definition of this term in ISO/IEC 26550. The definition in this document is
more specific to feature-based PLE and the PLE factory configurator (3.12) approach of producing product asset
instances from shared asset supersets.
4 Overview of feature-based product line engineering
4.1 General
This clause gives a brief informational overview of feature-based product line engineering, as a way
of introducing key concepts that are important for understanding the purpose and content of this
document.
Software and systems product line engineering emerged some time ago as way to engineer a portfolio
of related products in an efficient manner, taking full advantage of the products’ similarities while
respecting and managing their differences. Here “engineer” means all of the activities involved in
planning, producing, delivering, deploying, sustaining, and retiring products. Born in the software
engineering field in the 1970s and 1980s and based largely on the concept of software reuse, PLE has
long been known for delivering significant improvements in development time, cost, and quality of
[1]
products in a product line .
Early attempts to capture and codify best practices recognized a dichotomy between two sides: product
content that applies to multiple products and product content specific to a single product. Some referred
to the two sides as domain engineering and application engineering, respectively, while others referred
[1]
to core asset development vs. product development . Application engineering was often said to include
creating any content that happened to be used only in a single product, and promoting that content to
domain status only if subsequently used in more. Application engineering included the obligation to
choose and carry out a production strategy – that is, a way to turn the shared assets into products –
that was potentially different for each type of shared asset, and was often manual and therefore labour-
intensive and error-prone. Whatever they were called, the two sides stood on roughly equal footing in
terms of the effort required to execute.
4 © ISO/IEC 2021 – All rights reserved

However, starting in the early 2000s, the advent of industrial-strength and commercially available
technology designed specifically to support PLE enabled the rapid emergence of a specialization of PLE
[5]
practices. This approach is called feature-based software and systems product line engineering .
Under this approach, the technology just mentioned allows application engineering, which was so
important under the “classic” PLE approach, to shrink to almost nothing. Products are produced through
the use of high-end industrial-strength automation that configures the shared assets appropriately
for each product. Feature-based PLE explicitly declines to configuration-manage or change-manage
product versions. Instead, the shared assets (and not the individual products or systems) are managed
under CM (configuration management). A new version of a product is not derived from a previous
version of the same product, but from the shared asset supersets themselves. Additionally, any defects
are fixed in the shared assets, not the products. The affected products will then be regenerated, into
a form suitable for testing and deployment. Since regeneration has a low and fixed cost, it matters
very little whether 2 or 200 or 2000 products need to be regenerated. Thus, fixing a defect, making a
systematic enhancement, or carrying out any other kind of multi-product change becomes much more
[4]
economical .
4.2 to 4.4 describe a few more of the key ways that feature-based PLE differs from its antecedents.
4.2 Shared assets
Shared assets are the “soft” artefacts associated with the engineering lifecycle of the products,
the building blocks of the products in the product line. Assets can be whatever artefacts that are
representable digitally and either compose a product or support the engineering process to create a
product. Examples include, but are not limited to, the following:
— requirements;
— design specifications and design models for mechanical, electrical, and software;
— software source code and build files;
— test plans and test cases;
— user documentation, repair manuals, and installation guides;
— project budgets, schedules, and work plans;
— product calibration and configuration files;
— data models;
— process descriptions;
— parts lists and mechanical bills-of-materials;
— engineering drawings;
— electrical circuit board and wiring harness designs;
— training plans and training materials;
— skill set requirements;
— manufacturing plans and instructions;
— shipping manifests;
— marketing brochures;
— product descriptions;
— contract proposals.
© ISO/IEC 2021 – All rights reserved 5

Shared assets are engineered to be used (shared) across the product line. All of this was true before,
but in feature-based PLE, shared assets take the form of supersets, meaning that any asset content used
in any product is included. For example, a shared asset of requirements contains all of the requirements
across the product line; a shared asset of computer software source code contains all of the source
code; and so forth.
The virtue of this approach is that every piece of content for the product line, no matter in which
products it is used, is only created, stored, and maintained once. There is no duplication or replication
of asset content at all. This elimination of duplication (and elimination of replication of work across
[5]
duplicates) is where feature-based PLE derives its savings .
The shared asset supersets include variation points, which are places in the asset that denote content
that is configured according to the feature selections made for the product being built. When a product
is built, a statement of the product’s distinguishing characteristics – its features – is applied to “exercise”
these variation points (that is, cause the content associated with each variation point to be configured
in a way to meet the needs of the product).
Co
...