What Is Functional Decomposition? Functional Decomposition In A Nutshell

Functional decomposition is an analysis method where complex processes are examined by dividing them into their constituent parts. According to the Business Analysis Body of Knowledge (BABOK), functional decomposition “helps manage complexity and reduce uncertainty by breaking down processes, systems, functional areas, or deliverables into their simpler constituent parts and allowing each part to be analyzed independently.

Understanding functional decomposition

In business, functional decomposition is commonly used to capture project requirements. If the strategy is used properly, the organization can produce more accurate time estimates and determine whether a project is on schedule. Importantly, it can also identify smaller functions contributing to project delays and help stakeholders develop a deeper understanding of key processes.

Some of the terms unique to functional decomposition are listed below:

  • Function – simply a task that is performed by a process, system, or device. Functions are expressed as a verb-noun phrase. For example, the functions of an ATM may include “reads cards” or “dispenses cash”.
  • Decomposition – the process of breaking down.
  • General function – a function that requires other functions to work in order to take place. 
  • Subfunction – a function that has to work for a general function to take place. 
  • Functional decomposition diagram – a diagram used to illustrate the hierarchical relationships between tasks and sub-tasks. Tree diagrams are commonly used because they clearly show how a large function can be split into many smaller functions. However, nested diagrams, flow diagrams, cause-effect diagrams, mind maps, and state transition diagrams can also be used.

Performing functional decomposition

In this section, we’ll take a look at a general approach to performing functional decomposition:

  1. Determine the most general function – in other words, what is the most general task a project needs to accomplish? It is important to be concise and identify a single function that best encapsulates a goal or objective. A short description of the general function should then be placed at the top of the diagram.
  2. Determine the closest subfunctions – these are the functions that must occur immediately before the general function. Each subfunction should be connected to the general function by drawing a line between them.
  3. Move down to the next subfunction level – for the subfunctions identified in step two, find the “second-order” subfunctions that must occur immediately before each and connect them with lines. This process should be repeated until the team arrives at the most basic functions which cannot be broken down any further.

Subjects of functional decomposition

During the introduction, we mentioned a few benefits of using functional decomposition during project management.

In truth, however, the applications of the approach are numerous. Here are just a few examples of subjects that can be separated into smaller parts:

  • Business processes – where functional decomposition can be used to clarify individual process steps to measure, manage, and optimize them.
  • Business units – in this case, decomposition is used to understand how the organization works by evaluating individual business units. The diagram used in this context is the organogram, which illustrates organizational structure and shows hierarchical relationships between employees, managers, and departments.
  • Solution component – where individual elements are built to facilitate solution design, implementation, or change. This is commonly used in Agile methodologies to plan and create products.
  • Product and service development – in this case, functional decomposition is used to analyze and improve product and service design and implementation.
  • Decision-making – lastly, the decomposition process improves decision-making by encouraging practitioners to identify key inputs, underlying models, outcomes, and dependencies.

Key takeaways:

  • Functional decomposition is an analysis method where complex processes are examined by dividing them into their constituent parts.
  • Performing a functional decomposition means first defining a concise general function that aligns with project goals or objectives. Functions and subfunctions are then illustrated with connecting lines to represent their hierarchical relationship.
  • Functional decomposition is perhaps most associated with project management, but the approach is also used to decompose business processes, business units, solution components, product and service development, and decision-making.

Connected frameworks

Cynefin Framework

The Cynefin Framework gives context to decision making and problem-solving by providing context and guiding an appropriate response. The five domains of the Cynefin Framework comprise obvious, complicated, complex, chaotic domains and disorder if a domain has not been determined at all.

SWOT Analysis

SWOT Analysis is a framework used for evaluating the business’s Strengths, Weaknesses, Opportunities, and Threats. It can aid in identifying the problematic areas of your business so that you can maximize your opportunities. It will also alert you to the challenges your organization might face in the future.

Pareto Analysis

The Pareto Analysis is a statistical analysis used in business decision making that identifies a certain number of input factors that have the greatest impact on income. It is based on the similarly named Pareto Principle, which states that 80% of the effect of something can be attributed to just 20% of the drivers.

Failure Mode And Effects Analysis

A failure mode and effects analysis (FMEA) is a structured approach to identifying design failures in a product or process. Developed in the 1950s, the failure mode and effects analysis is one the earliest methodologies of its kind. It enables organizations to anticipate a range of potential failures during the design stage.

Blindspot Analysis

A Blindspot Analysis is a means of unearthing incorrect or outdated assumptions that can harm decision making in an organization. The term “blindspot analysis” was first coined by American economist Michael Porter. Porter argued that in business, outdated ideas or strategies had the potential to stifle modern ideas and prevent them from succeeding. Furthermore, decisions a business thought were made with care caused projects to fail because major factors had not been duly considered.

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