## 3 Metadata Design
### Classification of Metadata Elements  
To capture the complexity of modern synchrotron-based research, FC-BENTEN organizes metadata into distinct, intuitively defined categories. These categories ensured comprehensive coverage of the experimental workflow from raw data collection to final analysis.  
**data_info:** General data descriptors, including unique identifiers, facility names, beamline details, and project information. This \"data biography\" traces how and when data were created, modified, or integrated into the system.  
**facility:** Operational conditions at the synchrotron facility and beamline encompassing the accelerator parameters, beam energy, and current. Such details allow the precise contextualization of any given dataset and support cross-experimental comparisons.  
**sample:** Information on each sample--unique ID, preparation method, chemical composition, or structural features. This category ensures that the fundamental characteristics of the studied materials are well documented.  
**measurement:** Details of the measurements performed, including methodologies, instrumentation, and acquisition time. These records enabled a clear link between the collected data and the conditions under which they were obtained.  
**dataset:** Parameters used for data calibration, preprocessing, and formatting. Storing these variables ensures the consistent application of analysis methods across multiple datasets, thus supporting a more reliable data interpretation.  
**analysis:** Analytical procedures and associated parameters, as well as references to the software or algorithms employed. By standardizing the recording of the analysis steps, this category facilitates reproducible and transparent data processing pipelines.  
entry: Attributes of individual data files (raw and processed) and their relationships with each other. Managing data in a structured list format enables researchers to track the progression from raw input to the final analyzed results, ensuring a clear lineage and reducing confusion when revisiting datasets after long periods.  
This hierarchical organization of metadata, managed using machine-readable formats such as YAML [39] or JSON (JavaScript Object Notation) [40], addresses the limitations of earlier practices such as embedding experimental details in filenames or relying on file timestamps. Instead, it paves the way for seamless data integration with external platforms, reliable links between related experiments, and improved interpretability.  
FC-BENTEN's metadata schema builds upon the foundational framework of the SPring-8 XAFS standard sample database [41] but has been extensively tailored to meet the specific requirements of the platform. These adaptations enhance the practical utility of the metadata in synchrotron-based research, thereby providing a robust foundation for advanced data management and analysis. Examples of metadata elements relevant to the XAFS measurements categorized by context are presented in Appendix A (Tables A1-A7). Each table focuses on a specific category, such as data_info (Table A1), sample (Table A2), and measurement (Table A3), with detailed attention paid to their respective metadata structures.