Understand how work is done, and describe it in terms of flow, time, or elements. 

Functional Analysis is an umbrella term for a variety of methods that can be used early in the system development process (Nemeth, 2004). The types of questions that can be answered using function analysis include:

1. What functions need to be performed? And in what sequence? 
2. Who or what is responsible for (or best suited for) performing certain activities and functions?
3. What functions will the human perform? What functions will the system perform? 
4. How will humans and the system interact adaptively to perform functions?
5. How will information flow across multiple system elements?

Functional Analysis techniques can be sorted into three categories of methods: Flow Analysis, Time Line Analysis and Network Analysis. (Laughery and Laughery, 1987: 329-54). 

Flow Analysis can be used to reveal the functions that a product or system is intended to perform and to depict their order.  The method tracks how people or materials flow from one place to another, or from one operation to another.  

Time line analysis is used to account for the flow of functions, people, or materials over time.   

Network analysis accounts for relationships among system elements. It can include, for example, relationships among multiple operators (engineers, conductors, and dispatchers) and how information flows across those nodes. 

Results from these methods can be depicted using process charts, flow diagrams, timelines, interaction matrices, and link analysis diagrams.  Similar to activity analysis, understanding functions and operator workflow can help to identify demands on attention (Nemeth, 2004) that should be considered and addressed in system design. It can also ensure that the system meets the needs and addresses the constraints of its users -- contributing to system safety, reliability, efficiency, and resilience.

Tips for Performing Functional Analysis

• As a foundation for performing a functional analysis, the investigators should define a set of functions (i.e., What will be done by the system)
• It is important to capture and visually depict several items including: 
  • The sequence or flow of functions and activities
  • Elements of the system and how they interact with one another
  • Information needed to perform each function, action, or decision
  • How information flows across system elements and over time
• Developing visual representations of the analysis results enables investigators to detect patterns that might not otherwise be evident.