Purpose

Functional Decomposition helps manage complexity and reduce 

uncertainty by breaking down processes, systems, functional areas, or deliverable into their simpler constituent parts and allowing each part to be analyzed independently.

Business Analysis Body of Knowledge® (BABOK®)

Functional Decomposition is the method of analysis that breaks the complex process to show its individual elements. A function is task in a process whereby decomposition refers to breaking down a process in to smaller sections. IT is used to facilitate the understanding and management of large and complex processes. Functional decomposition helps to solve the complex problems and also in the development of business operations, computer programming, machine learning, and a variety of other fields. It refers to the process of analyzing the links and relationships between all the components that create a functional relationship so that the original function can be understood easily and clearly. The decomposition of the process in to smaller sub-functions can help the project managers to determine how the individual function helps to achieve the project goal.

Functional decomposition approaches the analysis of complex systems and concepts by considering them as a set of collaborating functions, effects, and components. The depth of decomposition may vary depending on the nature of the components and objectives. The process of breaking down larger components into smaller sub-components allows scaling, tracking, and measuring work effort for each of the components. Functional decomposition assumes that the sub-components can completely describe their parent components. It also facilitates evaluation of the success of each sub-component as it relates to other larger or the smaller components. The sub-component in the functional decomposition can have only one parent component when developing the functional hierarchy.

Some of the articles related to Functional Decomposition techniques are as follows,

• Functional Decomposition - https://www.tutorialspoint.com/software_testing_dictionary/functional_decomposition.htm
• Overview of Functional Decomposition - https://www.sciencedirect.com/topics/engineering/functional-decomposition
• Uses of Functional Decomposition - https://ndiastorage.blob.core.usgovcloudapi.net/ndia/2011/system/13165_MinchalaWednesday.pdf
• Making of Functional Decomposition - https://sourcemaking.com/antipatterns/functional-decomposition
• Value of Functional Decomposition - http://web.cecs.pdx.edu/~mperkows/PerkowskiGoogle/III-1.pdf
• System Based Approach to Functional Decomposition - https://www.aviationsystemsdivision.arc.nasa.gov/publications/2013/AIAA-2013-4241.pdf
• Fundamental of Decomposition - https://ocw.mit.edu/courses/aeronautics-and-astronautics/16-842-fundamentals-of-systems-engineering-fall-2015/lecture-notes/MTI16_842F15_Ses4_Con_Syn.pdf
• Advances in Functional Decomposition - https://core.ac.uk/download/pdf/11433411.pdf
• Event Based Functional Decomposition - https://www.researchgate.net/publication/336765369_Event-based_functional_decomposition
• Micro services using Functional Decomposition - https://www.researchgate.net/publication/326901590_Identifying_Microservices_Using_Functional_Decomposition
• Regional Approach to Functional Decomposition - https://arxiv.org/pdf/cs/0611024.pdf
• Functional Decomposition Process - https://apps.dtic.mil/dtic/tr/fulltext/u2/a543217.pdf
• Role of Functional Decomposition - https://pdfs.semanticscholar.org/abc2/c9698a2b520e453a6e5bd89c702c8ee8399a.pdf

The purpose of Functional Decomposition diagram is to show on a single page the capabilities of an organization that are relevant to the consideration of an architecture. By examining the capabilities of an organization from a functional perspective, it is possible to quickly develop the models to understand the process easily. The main elements of the functional decomposition technique includes,

• Decomposition Objectives - Objectives of the functional decomposition both the process of decomposition and define what to decompose, how to decompose and how deeply to decompose.
• Measuring and Managing - To isolate specific manageable factors that contribute to the overall result.
• Designing - To simplify a design problem by reducing and isolating the object of design
• Analyzing - To study the essential properties and behaviour of the artifact.
• Estimating and Forecasting - To decrease the level of uncertainty by breaking down a complex value in to its constituent factors.
• Reusing - To create a reusable solution building block that serves a specific function for various processes.
• Optimization - To reduce the function cost and improves the process quality.
• Substitution - A Function that is easily replaceable without impacting the system as a whole.
• Encapsulation - Combing elements to make one element
• Subjects of Decomposition
• Business Outcomes - The outcome of the income, profit, expenses, volume of services, volume of production.
• Work to be Done - It will break the functions into phases, tasks, work activities, work items and deliverable.
• Business Process - To identify its constituent parts for the purpose of measuring, managing, optimizing its components.
• Functions - To enable its optimization or the implementation.
• Business Unit - To enable its reverse engineering and its design
• Solution Component - To enable its design, implementation or change.
• Activity - To enable its implementation, optimization, modification, measurement, and estimation
• Products and Services - To design, implement, and improve them
• Decisions - For enabling them by identifying their inputs, underlying models, dependencies, and outcomes.
• Levels of Decomposition - The appropriate level of functional decomposition defines where, why, and when to stop decomposing the subject in order to meet the analysis objectives.
• Representation of Decomposition Results - It allows the business analysts to both validate and verify the results and to use them to solve other tasks.
• Tree Diagrams - Represent the hierarchical partitioning of work and activities
• Nested Diagrams - Illustrate the hierarchical part-to-whole relationships between decomposition results.
• Use case Diagrams - Represent the decomposition of a higher level use case
• Flow Diagrams - Depict the results of the process or functional decomposition
• State Transition Diagram - Explain the behaviour of the object inside its composite state
• Cause Effect Diagram - Elaborate on events, condition, and effects involved in producing a complex outcome.
• Decision Trees - Detail the structure of the complex decision and its potential outcome
• Mind Map - Represent information in categorizes
• Component Diagram - Depicts how the components are wired together to form a larger components

Business Analysis Body of Knowledge® (BABOK®)

Some of the books for Functional Decomposition techniques are,

• Functional Decomposition: Breaking the things down into their components | Paul F. Kisak | https://www.amazon.com/Functional-Decomposition-Breaking-Fundamental-Components/dp/1517772923/ref=sr_1_1?dchild=1&keywords=functional+decomposition+books&qid=1592201345&sr=8-1
• Functional Decomposition with Application | Christoph School | https://www.amazon.com/Functional-Decomposition-Applications-FPGA-Synthesis/dp/0792375858/ref=sr_1_12?dchild=1&keywords=functional+decomposition+books&qid=1592201513&sr=8-12