Functional needs analysis
Why carry out a functional needs analysis?
Before embarking on the design or redesign of a product or service, it is essential to question the real needs of its future users. This is where the functional analysis of the need comes in. By clarifying and prioritizing the expected functions, we reduce the risks of misunderstandings and gain in efficiency .
Simple definition : Functional analysis of the need consists of describing what a system (website, application, product, etc.) must do to fulfill its role, without going into technical details.
Main objective : Align all stakeholders around a common vision and avoid omissions.
Benefits :
- Better targeted features
- Fewer backtracking and costly corrections
- Greater user satisfaction
In the following sections, we will see two simple methods for conducting this analysis: the octopus diagram and the FAST method .
The OCTOPUS diagram
The octopus diagram (also called an “interaction diagram”) is a visual tool to quickly identify:
- External elements : everything that interacts with your future product (customers, suppliers, other systems, etc.).
- Core service and control features : what your product “must do” to serve these external elements.
How to build it?
1. Place the product in the center : Imagine a circle in the middle of your sheet or software.
2. Draw the “tentacles” : around the circle, each tentacle represents an actor or an external system (e.g.: client, third-party software, delivery service).
3. List the interactions : for each tentacle, ask yourself the question: The product must allow the external element to…
The external element must allow the product to…
Write down each function with a verb : for example, “place an order”, “provide bank details”, “send a notification”.
Example :
- The e-commerce site must allow the customer to select products , place an order , pay online , etc.
- The customer must allow the site to collect their payment information , identify their preferences , etc.
Benefits
- Visual clarity : At a glance, you see all stakeholders and their interactions.
- Rapid inventory of needs: Each interaction translates directly into one or more functionalities.
- Collaborative : The diagram is easily developed in a group, which encourages the exchange of ideas and cross-validations.
The FAST method
The FAST (Function Analysis System Technique) method is based on systematic questioning to clarify and prioritize needs. It focuses on two key questions: Why? and How?
Principle of “Why?” and “How?”
-
For what ?
For each feature or need identified, we ask ourselves why it is necessary. This approach allows us to verify the real usefulness of a function, or even to discover a more global need or a broader strategic objective. -
How ?
Once the why is defined, we ask ourselves how to satisfy this need. This leads to listing sub-functionalities or technical solutions.
Example :
- To create a personalized account, gain loyalty, and facilitate access to certain services.
- By integrating a registration form, an email verification system and a secure database.
Putting into practice
1. Start a brainstorming session :
Bring together the project team (marketing, technical, design, etc.) and list the main functions expected.
Question each function : Why is it important?
2. Prioritize the answers and ask the question How can we answer them?:
- The main functions (those which directly respond to the major need).
- Secondary or service functions (which enhance the experience or meet additional needs).
- Constraint functions (legal obligations, security constraints, standards, etc.).
Advantages of the FAST method
- Clarity and relevance : Asking “Why? How?” eliminates unnecessary features and highlights those that are truly essential.
- Global vision : The approach makes it possible to organize needs in the form of a tree structure, facilitating their reading and understanding.
- Constructive dialogue : Discussions around “Why?” and “How?” engage the team in a participatory approach, avoiding misunderstandings and promoting better cohesion.
With the FAST method, you get a precise map of your priorities and obligations. You can then consolidate this analysis with the Octopus diagram , which offers a more “visual” view of the interactions between your system and its environment.
