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Next Generation XAFS Data Library

This page is a Work-in-Progress Proposal for how to build a ''Next Generation XAFS Data Library'' The main idea is to allow XAFS Data Library that

1. facilitate the exchange XAFS spectra, particularly on model compounds, such as found in Model Compound Libraries.
2. store and manage multiple spectra, but still easily export to plain ASCII files.
3. allow users to have public and private libraries of spectra.
4. make it easy to share sets of XAFS spectra.

To date, there have been several Web-based Databases. While these all organize XAFS spectra on model compounds, they all have shortcomings such as incomplete data, difficulty of adding new data, and incompatible formats.

The aim here is to create a way to store multiple XAFS spectra in a manner that can be used within dedicated applications and embedded into existing data processing software with minimal effort. This will also alleviate many of the problems associated with the current databases.

• Motivation
• Implementation Overview
  • Development Code and Data
  • Why SQLite
  • Challenges Using SQL Tables for Numerical Array
  • Using JSON to store array data
  • Other Challenges When Using SQLite
• Tables and Database Schema
  • Spectra Table
    • Data storage
    • Encoding calculations
    • Energy units
  • Sample Table
  • Crystal_Structure Table
  • Ligand Table
  • Person Table
  • Citation Table
  • Format Table
  • Suite Table
  • Rating Table
  • Monochromator and Mode Tables
  • Beamline and Facility Tables
  • Element and Edge Tables

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Supported Low-Level Data Formats

Initially, the principle data format for the XAS Data library will be Internally Stored, JSON-encoded data arrays. Storing data internally has the advantage of preserving the database as a single file. JSON-encoded arrays have the advantage of being readily useful to many languages and environments. Alternate internal formats could be allowed, but no such formats are yet identified.

External data

Example Queries

Programming Interface(s)

References, External Links

• XAS Data Interchange format
• Talks from January, 2010 Workshop on HDF5 for Synchrotron Data
• Workshop (April 2011) on Improving Data for XAFS