# A.5 Duality of architectural decomposition, ISO 42024 ## Published contents Contents1 Scope2 Normative references3 Terms and definitions4 Architecture concepts4.1 Overview4.2 Architecture and architecting4.3 Architecture design and solution design4.4 Architecture definition and communication4.5 Stakeholder concerns and architectural aspects4.6 Architecture viewpoints and architecture views4.7 Architecture frameworks and architecture description languages4.8 Architecture descriptions and architecture models4.9 Reference architectures and reference models4.10 Life cycle and life history4.11 Architecting precepts5 Architecting principles5.1 Introduction to the principles5.2 Principles about the purpose of an architecture5.3 Principles about the focus of an architecture5.4 Principles about architecting outcomesTerms 3.2 Architecting concepts 3.2.1 Architecture3.2.2 Architecture feature3.2.3 Architecting3.2.4 Architecting principle3.2.5 Architecture principle3.2.6 Architecture framework3.2.7 Reference architecture3.3 Entity related concepts 3.3.1 Entity of interest3.3.2 Solution entity3.3.3 Environment3.3.4 Context3.3.5 Enterprise3.3.6 System3.3.7 Aspect3.3.8 Dimension3.4 Architecture design concepts 3.4.1 Design (noun)3.4.2 Architecture design3.4.3 Architecture information package3.4.4 Engineering effort3.4.5 Solution design3.4.6 Solution information package3.4.7 Stakeholder3.4.8 Stakeholder perspective3.4.9 Concern3.5 Architecture description concepts 3.5.1 Architecture description3.5.2 Solution description3.5.3 Architecture view3.5.4 Architecture viewpoint3.5.5 Model3.5.6 Metamodel3.5.7 Reference model3.6 Entity life cycle concepts 3.6.1 Life cycle3.6.2 Life cycle phase3.6.3 Life cycle stage3.6.4 Life historyAnnexes A.1 Architecture design and solution related entitiesA.2 Architecture expressed as a set of modelsA.3 Life cycle and life history conceptsA.4 Enterprise and system conceptsA.5 Duality of architectural decomposition and architectural synthesisB.1 BackgroundB.2 Aligning architecture in designB.3 Duality of architectureB.4 Pursuit of opportunities Home / Annex A Annex A, Notes on terms and concepts · A.5 # Duality of architectural decomposition and architectural synthesis The subclause is the fifth note in Annex A, on the duality of architectural decomposition and architectural synthesis. It closes the annex with the two directions of architecture work: breaking an entity into parts, and composing parts into an entity. - annex section, status not stated in the public preview - Annex section - ISO/IEC/IEEE DIS 42024 - Last updated: 2026-10-21 ## What this unit settles The duality is a warning against one way thinking. Decomposition is the familiar direction: break the system into components. Synthesis is the other: show how parts compose into a whole with the required properties. A firm that only decomposes can describe structure but cannot show that the whole has the properties it needs. ## What to do in your practice For each architecture, record the decomposition tree and a synthesis argument for the top three whole entity properties. The synthesis argument names the parts, the interactions and why the property emerges. Where it cannot be written, the property is assumed rather than designed. Ask the review panel to explain how a whole entity property is achieved without referring to the decomposition diagram. If the explanation is a list of components, the panel is describing structure, not architecture, and the property is being assumed rather than designed. ## Who it binds The architecture practice, as a note. The public preview does not state the annex status, so this page does not claim one. ## Evidence an auditor or regulator asks for - The decomposition record and the synthesis argument. An auditor asks how the whole property is achieved, not only how the parts are organised. - The interactions that produce the property. Shows the mechanism. - A list of properties with no synthesis argument. Reveals the assumptions. - The review record. Shows the arguments were tested. Ask your teamWhich whole entity property in this architecture has no synthesis argument, only a decomposition diagram? ## Common gaps this page catches - Only decomposition is documented. - Whole entity properties are asserted without a mechanism. - Reviews test structure, not composition. ## What to prepare before publication Write synthesis arguments for the top three properties of one entity. Use them in the next design review. The properties without an argument become the review agenda. ## Common questions What does Duality of architectural decomposition and architectural synthesis mean in ISO 42024? The subclause is the fifth note in Annex A, on the duality of architectural decomposition and architectural synthesis. It closes the annex with the two directions of architecture work: breaking an entity into parts, and composing parts into an entity. What evidence should we keep for A.5? The decomposition record and the synthesis argument. The interactions that produce the property. A list of properties with no synthesis argument. ## Related units - 3.2.1 - 3.3.7 - 3.3.8 Source. ISO/IEC/IEEE DIS 42024, Annex A.5, published contents. Open the official record. Retrieved 21 October 2026. https://www.iso.org/obp/ui/en/#iso:std:iso-iec-ieee:42024:dis:ed-1:v1:en ISO catalogue record 87510, the status, stage and page count. Claim level: annex section, status not stated in the public preview. The annex title and subclause title are in the public preview. The body text is not public. Last updated: 2026-10-21 · Markdown version · Check your practice Source: https://iso-42024-revision-checker.theartofservice.com/annex-a/duality-of-decomposition-and-synthesis/