After three successful versions of the Workshop on Collaborative Technologies and Data Science in Smart City Applications (CODASSCA 2018, 2020, and 2022) we are glad to present proceedings of the fourth version held at the American University of Armenia (AUA), October 3-6, 2024 in Yerevan, Armenia. Data Science and Reliable Machine Learning (ML) presents seventeen selected and carefully revised papers, which are available at the start of the workshop in the Open Access Proceedings and as a printed version. Society, technologies, and sciences are undergoing a rapid and revolutionary shift towards the integration of artificial intelligence into every system that people use in everyday life to create smart environments (SmE) through ambient intelligence (AmI) in highly connected and collaborative scenarios. The main source and asset for making smart systems is data, produced today in extraordinary large quantities. Data volumes are growing rapidly due to environmental sensor reading, sensor networks, broadband services, multimodal communication, whereas pervasive and embedded computing is enhancing the capability of everyday objects and easing collaboration among people. Data from all areas of daily life that are increasingly accessible to a broad public enable the conception, creation, calibration, and validation of a process or complex systems. However, this requires international standards for data quality and access. Mobile systems could enhance the possibilities available for designers and practitioners. Effective analysis, quality assessment and utilization of big data is a key factor for success in many business and service domains, including the domain of smart systems. Major industrial domains are on the way to perform this tectonic shift based on Big Data, Artificial Intelligence, Collaborative Technologies, Smart Environments (SmE) supporting Virtual and Mixed Reality Applications, Multimodal Interaction and Reliable Visual and Cognitive Analytics. However, many requirements must be fulfilled and complexities resolved before we can effectively and efficiently turn the huge amount of generated data into information and knowledge. The first one is to ensure data quality, which includes accuracy and integrity of the obtained data, timely delivery, suitable quantity, etc. Privacy and security requirements and thorough end-to-end rights complement realization and deployment of modern design, software development and evaluation tools. The second one is to create understandable models, which can turn data into valuable information and then into knowledge. A general challenge is the low interpretability of various artificial intelligence (AI) approaches and ML models, for which it is important that data scientists design the models, users understand results and developers debug and improve the models. The increasing complexity, limited explainability, and interpretability of the complex ML models make it difficult to address the emerging requirements for acceptance of these models and hinders their applications in industrial and mission critical scenarios. Therefore, explainability, interpretability, transparency, and accountability of ML models and systems need to be further developed for an effective use of AI technologies. They are a prerequisite for a reliable application of AI within many problem areas, e.g., natural language processing, risk prediction in healthcare, fault/anomaly detection, computer vision or classification and regression under uncertainty, which are significant ML tasks. Researchers and practitioners working on theoretical and practical aspects of data science and reliable machine learning, as well as related and fundamental topics of statistical analysis, information transfer and processing were invited to attend this workshop. The volume consists of the front matter and three thematic sections with seventeen peer-reviewed contributions. The editors would like to express their gratitude to the Foundation for Armenian Science and Technology, the German Research Foundation (DFG) and the German Academic Exchange Service (DAAD) for funding their activities; to Yanling Chen, Rubina Danilova, Amalya Hambardzumyan, Ashot Harutyanyan, and Gregor Schiele for their ongoing encouragement and support, our reviewers and to all participants for their presentations and contributions to the workshop and this proceedings volume. We are particularly grateful to the director of the Martiros Sarian HouseMuseum in Yerevan, Mrs. Rouzan Sarian, for allowing us to use her grandfather's painting of Aragats as the cover picture for this volume. Yerevan, Tsukuba, Duisburg, October 2024