XAS Database (XASDB): FAIR Spectral Repository

• XASDB is a comprehensive, open-access repository for X-ray absorption spectroscopy data that adheres to FAIR principles.
• It integrates browser-based processing and standardized metadata to harmonize, visualize, and analyze complex spectral datasets.
• The platform enables collaborative research and advanced machine learning applications across materials, chemistry, and biological sciences.

The XAS Database (XASDB) is a comprehensive open-access spectral repository designed to store, manage, process, and disseminate high-quality X-ray absorption spectroscopy (XAS) reference data. Developed and hosted by the Canadian Light Source (CLS), XASDB addresses a critical need for robust, FAIR (Findable, Accessible, Interoperable, Reusable) data infrastructure as XAS experiments at global synchrotron facilities produce ever-larger and more complex datasets (Spasyuk, 16 Sep 2025). This platform integrates browser-based processing capabilities, standardized metadata, diverse export options, and collaborative tools, advancing both research productivity and open science in materials, chemical, and biological domains.

1. System Architecture and Data Management

XASDB is built on a client-server architecture utilizing Node.js for server-side operations and MongoDB for flexible, schema-less data storage. Node.js provides high concurrency through asynchronous, event-driven processing, well-suited for fast retrieval and robust handling of large spectral datasets typical in XAS workflows. MongoDB’s document-oriented structure enables storage of heterogeneous XAS records, including data generated by differing beamlines and experimental conventions. A data parsing module is responsible for ingesting, normalizing, and standardizing input files—regardless of their provenance—ensuring all spectral records and metadata (e.g., energy axis, μ(E), element, beamline) conform to a unified schema upon storage. This backend design is critical for systematic aggregation, harmonization, and long-term reliability of reference spectra spanning 40 elements and more than 324 chemical compounds.

2. Integrated Browser-Based Data Processing

A key innovation of XASDB is the XASproc JavaScript library, which enables high-performance, browser-based XAS data processing independent of desktop installations. XASproc supports:

• Absorption coefficient normalization and baseline correction using polynomial and B-spline fitting, interpolation, and Savitzky–Golay smoothing
• Determination of the absorption edge ($E_0$) using smoothed first derivative, first-order, and second-order derivative methods
• Automated background subtraction (spline-based or weighted polynomial-based)
• EXAFS extraction: The oscillatory part $\chi(k)$ is extracted post-background subtraction and can be k-weighted as $\chi_k^{(n)}(k) = k^n \cdot \chi(k)$ for $n=0,1,2,3$
• Fourier transformation routines translating k-space to R-space via:

$$\chi(R) \approx \sqrt{\frac{2}{\pi}} \sum_{i} \chi_k(k_i) W(k_i) e^{-2ik_iR} \Delta k$$

• Determination of $\mu(E)$ in transmission mode is performed using the Beer–Lambert law: $\mu(E) = \frac{1}{x} \ln(I_0/I_t)$

By enabling all these steps natively in the browser, the platform eliminates dependencies on traditional desktop packages used for XAS processing (e.g., Athena, Larch), democratizing access and bolstering cross-platform compatibility.

3. Visualization and User Accessibility

XASVue, the client-side spectral viewer within XASDB, delivers an installation-free, interactive experience for XAS data analysis. It is constructed using pure JavaScript (Vanilla JS) and the Bootstrap CSS framework for universal device and OS compatibility. ECharts.js is leveraged for high-performance dynamic plotting, supporting:

• Overlaying multiple spectra for preliminary linear combination fitting (LCF)
• Real-time zoom, axis adjustment, and panning
• Immediate inspection of background subtraction, normalization, and EXAFS transformations

The tool’s interface design explicitly mimics popular desktop XAS packages, lowering the cognitive load for expert users while making advanced analysis features accessible without installation barriers.

4. Metadata, Export, and FAIR Principles

XASDB is fully aligned with FAIR data standards. Each spectral entry is accompanied by standardized, rich metadata which includes sample ID, beamline details, elemental composition, preparation method, and measurement conditions. Dual data export is supported:

• Native beamline output format, preserving original data structure for traceability
• XDI (X-ray Data Interchange) format, a standardized and interoperable schema facilitating analysis across diverse software environments

All data are distributed under the Creative Commons CC BY 4.0 license, promoting unrestricted reuse, remixing, and redistribution with proper attribution. The parsing module’s normalization/standardization routines are essential for harmonizing records ingested from heterogeneous sources.

5. Analytical Applications and Scientific Impact

The platform’s reference data and browser-integrated analysis tools enable:

• Linear Combination Fitting (LCF): The provision of standardized, baseline-corrected spectra allows users to perform LCF directly in the browser, aiding phase identification and quantitative analysis.
• Machine Learning: The extensive, well-annotated database—encompassing both spectral and metadata—constitutes a resource for ML-driven tasks such as automated phase identification and oxidation state assignment.
• Educational Resources: The browser-based, installation-free interface is designed for instructional use, supporting didactic exploration for students and educators.
• Multidisciplinary Reach: The ready availability of high-quality, reference spectra accelerates research in materials science, chemistry, environmental science, and biology by serving as a benchmark for experimental and computational investigations.

6. Innovations and Future Development

XASDB refactors the conventional desktop XAS analysis paradigm to a fully web-centric, scalable approach. The key innovations include:

• High-performance, in-browser XAS data processing via XASproc, obviating the latency and access issues of desktop tools.
• Automatic control for advanced operations (windowing functions, adaptive spline-fitting, background quality metrics) natively implemented in JavaScript.
• A modular backend (Node.js/MongoDB) that readily ingests and normalizes disparate file formats from a spectrum of synchrotron facilities.

Future development tracks cited in the work are:

• Evolution into a community-driven repository, enabling external user contributions via secure upload
• Greater automation in preprocessing routines, including adaptive fitting and background evaluation
• Deeper integration with machine learning and advanced fitting algorithms to support real-time, intelligent phase or state identification
• Expansion of browser-based analytics, potentially incorporating routines historically confined to specialized desktop packages

7. Role in the Global XAS Data Ecosystem

XASDB’s open access, interoperable, and web-accessible infrastructure situates it as a central resource for the global XAS community. By harmonizing reference spectra, metadata, and analytical workflows under a FAIR and open model, it facilitates cross-laboratory collaboration, reproducible research, and accelerated discovery science (Spasyuk, 16 Sep 2025). Its design anticipates and serves the growing needs of user bases in data-driven XAS research, high-throughput machine learning, in situ/operando analytics, and educational initiatives.