ISO/IEC 19086-2:2018

INTERNATIONAL ISO/IEC
STANDARD 19086-2
First edition
2018-12
Cloud computing — Service level
agreement (SLA) framework —
Part 2:
Metric model
Informatique en nuage — Cadre de travail de l'accord du niveau de
service —
Partie 2: Modèle métrique
Reference number
©
ISO/IEC 2018
© ISO/IEC 2018
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ii © ISO/IEC 2018 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms . 2
5 Conformance . 3
6 Metrics overview . 3
6.1 General . 3
6.2 Background . 3
6.2.1 Choosing a cloud service . 3
6.2.2 Convert requirements to agreement . 4
6.2.3 Ensure the agreement is being met . 5
6.3 Metrics . 5
6.4 Cloud service metrics (CSMs) . 5
6.4.1 Major stakeholders . 6
6.4.2 CSM usage categories . 7
7 Metric model overview .10
7.1 General .10
7.2 Basic concepts .11
7.2.1 Introduction .11
7.2.2 Cloud service level objectives and cloud service qualitative objectives .11
7.2.3 Metric data format .12
8 Metric model .12
8.1 Metric model development .12
8.1.1 Metric model specification .13
8.1.2 Use of UML class diagrams and textual descriptions .13
8.1.3 Metric model description .13
8.1.4 Extending the metric .14
8.1.5 Metric model details .14
Annex A (informative) SO and SO evaluation .18
Annex B (informative) Metric — Table form .20
Annex C (informative) CSM examples .23
Annex D (normative) XML schema .36
Bibliography .39
© ISO/IEC 2018 – All rights reserved iii

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.
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 ISO documents 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 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 of 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 www .iso
.org/iso/foreword .html.
This document was prepared by Technical Committee ISO/IEC JTC1, Information technology,
Subcommittee SC 38, Cloud Computing and Distributed Platforms.
A list of all parts in the ISO 19086 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/members .html.
iv © ISO/IEC 2018 – All rights reserved

Introduction
The measurement of properties of cloud services, especially for the purpose of cloud service level
agreements (SLAs), presents many challenges, which inhibit the uptake of cloud services and inhibit
the overall effectiveness of the cloud services marketplace. Metrics in practice are usually described
using natural languages, typically in ‘plain English’, which is often difficult to understand, compare, and
implement. Such definitions of metrics lead to many problems. Typical concerns include:
— Clarity: The metric definition may be incomplete, ambiguous, illogical, self-contradictory, or not
defined at all. For example, cases exist where ‘availability’ is defined in ways which have little to do
with generally accepted definitions of ‘availability’; where the definition is such that the service can
be unavailable for the majority of the time yet the metric will show 100 % availability; where the
metric requires continuous monitoring, which is actually not possible; or where the provider is able
to determine at its sole discretion what the result is.
— Comparability: It may be impractical or effectively impossible to compare different services
in terms of their promised service levels because of the significant inconsistency in how their
respective metrics and SLOs/SQOs are defined.
— Implementation: It may be impractical or even impossible to measure the metric in practice, and
to determine whether promised service levels have been met or not.
This document has been developed to help address these and similar concerns. It includes technical
content, but the high-level concepts are expected to be understandable by non-technical individuals
who understand the business context for metrics. It provides a metric model that defines the conditions
and rules for performing a measurement and understanding the result.
A metric complying with the model defined by this document addresses the concerns above:
— Clarity: A definition of a metric eliminates the ambiguities which currently exist in natural language
descriptions.
— Comparability: The structured nature of the metric facilitates the comparison of different metrics
and SLOs/SQOs based on a metric.
— Implementation: The structured representation of the information needed to measure a
characteristic facilitates the process of developing measurement tools. Likewise, if the metric is
found not to be implementable, then the metric will need to be revised so that it can be implemented,
and the structure of the technical specification is expected to facilitate this revision process.
The focus of this document is on metrics for cloud SLAs, but it is also usable for cloud service metrics
(CSMs) that are not included in cloud SLAs [such as ones used by cloud service providers (CSPs) for their
internal performance monitoring], and may also be usable for non-CSMs.
© ISO/IEC 2018 – All rights reserved v

INTERNATIONAL STANDARD ISO/IEC 19086-2:2018(E)
Cloud computing — Service level agreement (SLA)
framework —
Part 2:
Metric model
1 Scope
This document establishes common terminology, defines a model for specifying metrics for cloud
SLAs, and includes applications of the model with examples. This document establishes a common
terminology and approach for specifying metrics.
This document is for the benefit of and use for both cloud service providers (CSPs) and cloud service
customers (CSCs). This document is intended to complement ISO/IEC 19086-1, ISO/IEC 19086-3 and
ISO/IEC 19086-4.
This document does not mandate the use of a specific set of metrics for cloud SLAs.
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 17788, | ITU-T Y.3500, Information technology — Cloud computing — Overview and vocabulary
ISO/IEC 19086-1, Information technology — Cloud computing — Service level agreement (SLA)
framework — Part 1: Overview and concepts
W3C Recommendation 28 October 2004. XML Schema Part 1: Structures Second Edition . ht t p: //w w w .w3
.org/TR/xmlschema -1/
W3C Recommendation 28 October 2004. XML Schema Part 2: Datatypes Second Edition. ht t p: //w w w .w3
.org/TR/xmlschema -2/
3 Terms and definitions
For the purposes of this document,
...