## Materials and Methods  
### Design-Based Approach  
The design of applications for older adults has to meet one major requirement: user satisfaction. In this context, several approaches have been presented throughout the years that apply quality factors to achieve this goal. The user-centered design (UCD) consists of a methodology based on the user's interaction with an application through the development process [43; 44]. This process is composed of two stages: _discover_ (identification of requirements) and _design_ (definition of style and content). The _design_ stage also subdivides into _prototyping_ (GUI and functionality refinement) and _evaluation_ (tests with users).  
In the first stage, several separate meetings were arranged with the different stakeholders --three meetings with therapists and caregivers (four therapists and three caregivers) and three meetings with nutritionists (two nutritionists) to identify the major requirements of a food plan application, which are as follows:  
* The application should be intuitive and easy to use;
* The application should map the real concept of what a meal is and use visual markers for better identification of components;
* Make available a weekly list of meals provided by the nutritionist so that the caregiver or patient can plan and anticipate the meals for that week;
* Provide a detailed view of each meal and use visual markers for each food;
* Allow the change of food in a meal for an equivalent (with the same nutritional value);
* Register the consumption of macro-nutrients, micro-nutrients, and water consumed in each meal of the food plan;
* Provide the user with information on discrepancies between the defined nutrients and real consumption through statistics;
* Push notifications for scheduled meals.  
To acquire quantitative data, study participants were assigned several tasks to complete in the interface designed in Section 4.  
The second stage focused on the system's usability, and the users conducted tests. According to [45], four or five participants are enough to find 80% of usability problems. Based on the proposed methodology, it was essential to carry out evaluations to measure the impact on user satisfaction using two approaches: cognitive walkthrough [46; 47] and _user experience questionnaire_ (UEQ) [48]. For the first, the user receives a goal, searches in the interface, interacts with the interface, and provides feedback; in the second approach, applying the UEQ avoids extensive tests on the user interface that are time-consuming and involve costs [49]. UEQ combines attractiveness (users like or dislike the product), perspicuity (simple to become familiar with the product), dependability (the user perceives control over the interaction), efficiency (users perform their activities without exerting undue effort), novelty (uniqueness and innovation), and stimulation (fun and motivates the use of the product) measures, as well as a survey of 26 contradictory adjective pairs. The UEQ questionnaire contains a scale obtained from a benchmark that incorporates five quality levels: excellent (ranked in the top 10%), good (10-25%), above average (25-50%), below average (50-75%), and poor (\(<\)25%).  
Moreover, to link the interface to the general tendency to model and learn by analogy, we used metaphors created with conceptual models to enable users to draw on their existing knowledge to act on a non-familiar domain [50], as presented in Section 5.