###### Abstract  
To address the challenges of aging societies, various information and communication technology (ICT)-based systems for older people have been developed in recent years. Currently, the evaluation of these so-called active and assisted living (AAL) systems usually focuses on the analyses of usability and acceptance, while some also assess their impact. Little is known about the actual take-up of these assistive technologies. This paper presents a framework for measuring the take-up by analyzing the actual usage of AAL systems. This evaluation framework covers detailed information regarding the entire process including usage data logging, data preparation, and usage data analysis. We applied the framework on the AAL prototype CARIMO for measuring its take-up during an eight-month field trial in Austria and Italy. The framework was designed to guide systematic, comparable, and reproducible usage data evaluation in the AAL field; however, the general applicability of the framework has yet to be validated. active and assisted living; AAL; usage data; user interaction logging; framework for usage data evaluation 2020 10 38 (2020) 17 December 2019 19 December  
with the system [5; 8; 9]. Survey data reflect self-reports from users but may lack accuracy and details due to a range of possible response biases (i.e., systematic errors in answering survey questions). Response biases, such as limitations in the ability to recall past system interactions [10] or responses reflecting overly positive self-descriptions [11], may lead to over- or under-reporting of system usage. On the other hand, automatic recording of usage is less invasive. Automatically recorded usage data measure the use of a system without users always being aware of them being tracked, which is less prone to response bias than self-reporting. Usage data collection, however, also requires careful preparation to gain meaningful data, to avoid gathering a useless mass of data, and finally, to enable researchers to answer their research questions. Thus, careful planning and preparation of log data collection and analysis is essential to achieving good data quality and reliable results [5; 12]. Previous research on automatic usage recording has either focused on technical frameworks for usage measurement [13; 14; 15] or the user grouping/classification of usage patterns [16; 17; 18]. Topics less developed in previous work on usage measurement include the selection of the logging component(s) and data source(s), the determination of logging capacity, and ethical and data privacy considerations. Only a few AAL projects report the practice of automatic usage recording. In MobileSage, a technical framework for usage measurement was developed and used to adapt user profiles [8; 19]. In Zentr AAL, the actual utilization of system components and features by different user groups was analyzed [20]. To increase the use of automatic usage measurement in AAL projects, a comprehensive usage data evaluation framework is required to guide systematic, comparable, and reproducible usage data logging, preparation, and analysis that covers technical, ethical, and data protection requirements. This paper aims to contribute to the evaluation of AAL systems by proposing a standard for usage data evaluation and applying this for the first time to an AAL prototype, called CARIMO. The suggested usage data evaluation framework comprises all steps relevant for a comprehensive usage data collection and offers options for data collection and analysis. The framework and experiences in applying the framework for assessing the take-up of the AAL-prototype CARIMO aim to better guide future usage data collection and analysis in the research field of AAL. Researchers may use this framework for evaluating the take-up of AAL systems in a systematic, comparable, and reproducible manner. The remainder of this paper is structured as follows: In Section 2, the AAL prototype CARIMO is presented.