## 1 Introduction  
In today's rapidly urbanizing world, cities are expanding at an unprecedented rate, becoming home to an ever-growing population. This transformation presents significant challenges for policy-makers, urban planners, and local communities, with the central issue being how to ensure a high quality of life for all citizens. The United Nations' Sustainable Development Goal 11 (SG11) emphasizes the importance of creating cities and human settlements that are inclusive, safe, resilient, and sustainable [1, 2]. As cities evolve, the concept of \"smart cities\" has emerged as a promising framework for addressing these challenges [3, 4, 5, 6]. Smart cities leverage technology and data-driven solutions to enhance various aspects of urban living, aiming not only to improve infrastructure and services but also to promote an elevated quality of life (QoL) for residents. Qualityof life is central to smart city initiatives, serving as a critical measure of a city's success in meeting inhabitants' needs and expectations. There are two primary approaches for measuring quality of life at the local level: the objective approach and the subjective approach [7; 8; 9; 10; 11]. The objective approach relies on quantifiable indicators derived from publicly available statistical data. It focuses on measurable aspects of living conditions, such as income levels, employment rates, access to education, and healthcare facilities. By analyzing these indicators, researchers can assess the actual state of living standards within various communities, offering a comprehensive overview of societal conditions. In contrast, the subjective approach emphasizes individual perceptions and experiences regarding quality of life [12; 13; 14; 15; 16; 17; 18]. It gathers insights through surveys and questionnaires that capture respondents' opinions on various aspects of their lives, including satisfaction with personal circumstances, social relationships, and overall well-being. This approach recognizes that quality of life is inherently personal and can vary significantly among individuals based on their values, desires, and expectations. Subjective indicators are often assessed through satisfaction ratings in different life domains, offering a more nuanced understanding of well-being. Both approaches provide valuable insights into the factors influencing quality of life but from different perspectives. The objective approach delivers a concrete overview based on statistical data, while the subjective approach captures the complexities of personal experiences and satisfaction, making both approaches complementary in understanding QoL comprehensively. The use of questionnaire-based surveys is essential for measuring subjective quality of life (SQoL) in cities, providing a direct means of assessing residents' experiences and perceptions. A prominent example is the 'Quality of Life in European Cities' survey, which has been conducted every three years since 2004. This survey uses ordinal scales to evaluate key areas of urban living, yielding insights into satisfaction with employment, public transport, healthcare, education, recreation, and pollution levels. The primary aim is to monitor citizens' feelings about different facets of urban life, which is crucial given that cities generate the largest share of the EU's GDP, and drive economic growth and social policy development. Survey responses are collected on a 5-point measurement scale (e.g., 4--Very satisfied, 3--Rather satisfied, 2--Rather unsatisfied, 1--Very unsatisfied, with an additional category \"Don't know /No Answer/Refused\"). The ordinal scale from 1 to 4 captures ranked responses without assuming precise intervals between levels, providing insight into respondents' attitudes and preferences. However, during later analysis, responses are frequently simplified by merging categories, such as combining \"very satisfied\" with \"rather satisfied\", which may obscure subtle differences in satisfaction.