What's concretely the designer's mental model?

Question

In the book "The UX Book: Process and Guidelines for Ensuring a Quality User Experience", the authors mention in chapter 8.2 designer's mental model (also called conceptual model). They first define it as

DMM is a vision of how a system works as held by the designer.

and then

DMM is the designer's conceptualization of the envisioned system.

They say that the designer's mental model can be seen from three perspectives: ecological, interaction and emotional. However, IMHO, their definitions are a bit vague. They also do not give examples in the context of designing UI for web and mobile applications, which happens to be my case.

Suppose I am the designer of a UI for a mobile application whose purpose is to allow people to exchange, share and give away goods or items they no longer need. Given that I am the designer, then, I suppose, the designer's mental model is my mental model of how my mobile application works or should work.

But how would you define the designer's mental model if you were the designer of this specific application (i.e. what's your mental model about this application)? What would be your ecological, interaction and emotional perspectives of this application?

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Note: I am looking for a concrete answer to this specific example. I am not looking for other vague and general answers.

Answer 1

I have not read the text you reference, so I may have an incomplete understanding of the authors’ thoughts, but I have a few comments that hopefully help to clarify the questions you have. I think it is important to note that the designer’s mental model should not be defined by their own personal understanding of the app they are designing, but rather the understanding of the people who will be using the app.

The ecological, interaction and emotional perspectives of the mental model should be framed by the users’ experience in the real world situation (the transfer of goods). For example, how does emotion play a role when someone decides to exchange something they own? What stories would they tell about the item before they exchange it with someone else?

The authors may not have included detail on mental models in the context of UI design because the mental model should describe the users’ understanding of the real world situation. I see the mental model and UI as separate, but complimentary, areas. The UI should provide users with the ability to perform actions within the app that correspond to their mental model of the real world situation.