ISO/IEC TR 23951:2025

Technical
Report
ISO/IEC TR 23951
Second edition
Information technology — Cloud
2025-04
computing — Best practices for
using the cloud service level
agreement (SLA) metric model
Technologies de l'information — Informatique en nuage —
Bonnes pratiques pour l'utilisation du modèle métrique d'accord
de niveau de service (SLA) dans le Cloud
Reference number
© ISO/IEC 2025
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Published in Switzerland
© ISO/IEC 2025 – All rights reserved
ii
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms. 1
5 Structure of this document . 2
6 Motivation . 2
6.1 Preamble .2
6.2 Audience and some user categories .2
6.2.1 General .2
6.2.2 Cloud service customer (CSC) . .3
6.2.3 Cloud service provider (CSP) .3
6.2.4 Cloud service partner (CSN) .3
6.2.5 Regulators and policy makers .3
6.3 Usage patterns .4
6.3.1 General .4
6.3.2 Extract and clarify an existing metric description from an SLA . .4
6.3.3 Create and share a metric description .4
6.3.4 Compare metric descriptions .4
6.3.5 Share a common foundation for a set of metrics .5
6.3.6 Build a metrics catalogue .5
6.4 Examples of scenarios and roles involved in sharing metric definitions .5
7 The metric model in practice: templates . 6
7.1 A brief reminder of the metric model .6
7.2 A tabular representation .7
7.2.1 General .7
7.2.2 The tabular representation for the Metric element .8
7.2.3 The tabular representation for the Expression elements .9
7.2.4 The tabular representation for the Rule elements .10
7.2.5 The tabular representation for the Parameter elements .10
8 An example of metric definition: the cloud service mean response time metric .11
8.1 The cloud service mean response time metric: informal variant .11
8.1.1 Extracting metric elements from an SLA narrative .11
8.1.2 Using the tabular representation . 12
8.1.3 Overall structure of the metric . 13
8.2 The cloud service mean response time metric: more formal variant .14
8.2.1 A more formal variant of the metric .14
8.2.2 Adding a parameter .14
8.2.3 The metric rules . 15
8.2.4 The metric expressions . 15
8.2.5 Overall structure of the metric .16
8.2.6 Using constants .17
9 Guidelines for using the metric model with the tabular representation . 19
9.1 General .19
9.2 Guideline 1 about defining expression and rule languages .19
9.3 Guideline 2 about associating rules with expressions .19
9.4 Guideline 3 about relating expressions to each other . 20
9.5 Guideline 4 about the identifiers of metric elements . 20
9.6 Guideline 5 about rules specifically designed to support an expression . 20
9.7 Guideline 6 about the role of parameters .21

© ISO/IEC 2025 – All rights reserved
iii
9.8 Guideline 7 about representing constants .21
10 The simple cloud service availability metric.22
10.1 Measuring cloud service availability . 22
10.1.1 General . 22
10.1.2 Overall design approach . 22
10.1.3 SLA rules and metric rules . 22
10.2 The simple cloud service availability metric variant Simple_SAM_1 . 23
10.2.1 The Metric element . . 23
10.2.2 The metric rules .24
10.2.3 The metric expressions . 25
10.2.4 The metric parameters . 26
10.2.5 Overall structure of the metric . 26
10.3 The simple cloud service availability metric variant Simple_SAM_2 .27
10.3.1 Differences in metric design and assumptions .27
10.3.2 The Metric element . . 28
10.3.3 The metric rules . 28
10.3.4 The metric parameters . 29
10.3.5 The metric expressions . 30
10.3.6 Overall structure of the metric .31
10.3.7 An alternative metric design using the Configuration element option .32
Bibliography .33

© ISO/IEC 2025 – All rights reserved
iv
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 technica
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