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Validity & metadata

LEGEND uses a validity-based metadata model to describe which files are active for a given category and time. This tutorial explains the structure of validity entries and how to apply them in practice.

Validity entry structure

Each validity entry contains the following fields:

  • valid_from: timestamp indicating when the change becomes effective.
  • category: metadata category, e.g., "cal", "phy", or "all". The value "all" is its own category; it does not mean that the entry applies to every category.
  • mode: operation type, one of reset, append, remove, or replace.
  • apply: list of files affected by the operation.

Example:

- valid_from: "20221118T000000Z"
  category: "cal"
  mode: "append"
  apply:
    - /data/l200/partition1/cal/fileA.h5
    - /data/l200/partition1/cal/fileB.h5

Modes

  • reset: replaces the entire active file list with the entries in apply.
  • append: adds the listed files to the current active list.
  • remove: deletes the listed files from the current active list.
  • replace: substitutes one file for another.