Three Lines Model

The Institute of Internal Auditors' 2020 update of the "three lines of defense": the governing body oversees; management holds first-line roles (delivering products and services) and second-line roles (risk expertise, support and challenge); internal audit gives independent third-line assurance 1.

Developed in
ch. 12, The three lines, applied to AI
Chapters
ch. 12, Governance Program
Source
1 numbered reference, listed below

Where it is used

3 chapters of the Body of Knowledge use the term. Each link opens the first section that does.

Three Lines Model: mentions per chapter3 mentions of the term across 3 of the 23 chapters of the Body of Knowledge; the chapters the glossary cross-references are drawn solid.Cross-referenced chapterOther chapter10 Reading List: 1 mention10 Reading List112 Governance Program: 1 mention12 Governance Program113 Risk Management: 1 mention13 Risk Management1No mentions in the other 20 chaptersSource: the Body of Knowledgev0.5.0
Three Lines Model: mentions per chapter3 mentions of the term across 3 of the 23 chapters of the Body of Knowledge; the chapters the glossary cross-references are drawn solid.Cross-referenced chapterOther chapter00010203040506070810 Reading List: 1 mention1101112 Governance Program: 1 mention11213 Risk Management: 1 mention11314151617181920212223Source: the Body of Knowledge v0.5.0
Mentions per chapter How often each chapter names the term, with the chapters the glossary cross-references drawn solid. The longest bar is where to read the term in use; bars spread across many chapters mark a term that runs through the discipline.
Mentions as a table
Mentions of Three Lines Model per chapter
ChapterMentionsCross-referenced
00 Preface0No
01 Definition0No
02 Why Now0No
03 Values & Principles0No
04 The Stack0No
05 Patterns0No
06 The Role0No
07 Maturity Model0No
08 Regulatory Map0No
10 Reading List1No
11 AI Defined0No
12 Governance Program1Yes
13 Risk Management1No
14 Development0No
15 Deployment0No
16 Fairness & XAI0No
17 Incidents0No
18 EU AI Act0No
19 Privacy & AI0No
20 Existing Law0No
21 AI Laws Worldwide0No
22 Principles & Standards0No
23 AI Agents0No

Sources

  1. [1] The IIA's Three Lines Model: an update of the Three Lines of Defense (governing body; management's first- and second-line roles; internal audit as third line; third-line independence). The Institute of Internal Auditors. 2020-07. https://www.theiia.org/en/content/position-papers/2020/the-iias-three-lines-model-an-update-of-the-three-lines-of-defense/ (verified: primary)

Definitions of legal terms paraphrase the cited text, which governs. Dated statements are as of .

Cite this term

García Aibar, J. (2026). Three Lines Model. In AI Governance Engineering: The Thesis & Body of Knowledge (v0.5.0), Glossary. https://doi.org/10.5281/zenodo.22956197. https://aigovernanceengineer.com/glossary/three-lines-model. CC BY 4.0

BibTeX

@misc{aige2026threelinesmodel,
  author  = {Jorge García Aibar},
  title   = {{Three Lines Model}},
  note    = {Glossary, AI Governance Engineering: The Thesis \& Body of Knowledge, version 0.5.0},
  year    = {2026},
  doi     = {10.5281/zenodo.22956197},
  url     = {https://aigovernanceengineer.com/glossary/three-lines-model}
}