Cave, Knife, Features: how to design a relationship

“Why is it that when we encounter a variety of unusual natural objects, we know how to interact with them?”. That’s a question Don Norman asks in his book 'The Design of Everyday Things'. I thought about that when I was designing innovative features for the Rabo banking app. My team created ‘smart transfers’; a simple and easy-to-use feature for financially healthy living.

But how to define ‘simple and easy’? What might be easy for some could feel restrictive to others. How do we balance simplicity and possibilities? What kind of relationship can we design while people are using our product?

These are some of the questions I got from Norman, and he uses the term “affordance” to answer his question. Affordance refers to how an object could possibly be used. For instance, a chair can afford sitting and lifting for most people. But for relatively weak people who cannot lift a chair, it does not have that lifting affordance. The affordance of a design exists in the relationship between the qualities of the object and the abilities of the person interacting with it.

This principle can also be applied to digital products. In a way, to design for affordance means to design a relationship between a user and a product.

“Strong” vs “Weak” relationship design

In my experience studying and working in both Asia and Europe, I explored this idea in a bit broader sense using various design fields.

The term ‘Relationship design’ is referenced in lectures from Feng Guochuan (a Chinese architect) and Kenya Hara (one of the leading designers in Japan). I learned that we can construct a “Strong” or “Weak” relationship design. A “Strong” relationship design means it is strongly pre-determined how a product should be used. A “Weak” relationship suggests that the restriction is thin and soft – it’s up to the user to define how to use the product. Let’s look at some examples.


In architecture, the most common “Strong” relationship design is our own house. Most of our homes are designed based on functional requirements. A dining room is a place to eat, a bedroom is a place to sleep, and a living room is a place for family activities. The settings of all these spaces are purposeful and functional – their design is based on a strong pre-determined model.

With a “Weak” relationship design in buildings, you cannot clearly figure out what is the use of a particular part of the space. Imagine you were living in a natural cave: you can use the cave’s shape to create its usage. The concave surfaces can be used for sleeping, and the protruding areas could be used as benches. You can constantly define new uses of the cave.

Japanese architect Sou Fujimoto took this concept to design the ‘House NA’. The space inside of this house does not have a clearly defined function, and it depends entirely on the user’s own preferences.

Sou Fujimoto House NA with bright sunlight, and a family is living in there
Design Sou Fujimoto House NA. How it’s used depends entirely on the people’s preferences. Source: Archdaily, Photograph: Iwan Baan, Source: archdaily.


We can explain the “Strong” relationship model with another example. A German chef usually has a complete set of knives. The function of each knife is defined in the most rational and optimal way. Assorted sizes and shapes serve different purposes. Some knives even have a groove in the handle for the chef’s thumb, and even a best-defined position to hold the knife.

A Japanese chef, however, would normally use two knives at most to complete the job. This is because he can adjust the way he holds and uses the knife according to the food.

the left side is a set of German chef knives; the right side is a Japanese chef’s knife.
A German chef has a special knife for each purpose (left). A Japanese chef uses just one knife for everything (right). Source: Hinoki


We can also follow this model in digital design, for example when designing features for an app. For some people, the way to use the feature is probably highly predetermined, but for others it is not, based on their own daily experience.

So, will you design a “Strong” or “Weak” relationship? Will your design be restrictive on how people can use it? Or will you offer options to personalize it?


Sometimes predefined and highly restricted models work best. In other cases, users should have more freedom. From my experience, something in between often results in the best user experience. Take a group of input fields of an online form. All required fields need to be filled before going to the next page (“Strong”), but users can fill them in their own order (“Weak”).

a form to set a smart rule to prevent your bank account falling below a specific balance
A form to set a smart rule can have both a “Strong” and a “Weak” relationship with the user.

If it’s not critical for the technical feasibility of the design, it’s best to offer the users the possibility and freedom to explore the digital space in the way they want. So whatever you’re designing, ask yourself: what kind of relationship do I want my user to have with my design? Because in the end, design is not just about building a product. It’s about trying to create affordance, the relationship between people and the product.

About the author

Sijing Zhang
Senior Designer

Sijing is an experienced designer who has collaborated with teams in both Asia and Europe. As a thoughtful problem-solver, she brings a balance of functional and aesthetic to design. With expertise in branding and user experience design, she applies her creativity to projects across all stages.

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