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Output Layout and Naming

The layout system defines how converted outputs are named and organized on disk. It consumes structured metadata produced by specs and optionally remapped by context maps.

Layout logic is purely about paths and filenames. It does not inspect raw Bruker parameters and does not perform metadata mapping itself.

Purpose

Layouts are used to:

  • generate standardized directory structures
  • construct filenames from metadata fields
  • hide or expose metadata keys in paths
  • support project-specific naming conventions (for example BIDS-like layouts)

Layouts do not:

  • select scans (rules do that)
  • compute metadata values (specs do that)
  • remap values conditionally (context maps do that)

Data flow overview

Bruker parameters
    ↓
specs (info_spec / metadata_spec)
    ↓
context map (optional, runtime)
    ↓
layout (entries or template)
    ↓
output paths and filenames

Where layout configuration lives

Layout configuration can be defined in three places, evaluated in this order:

  1. Runtime context map (context_map.__meta__)
  2. Global config (config.yaml)
  3. Built-in defaults

The first definition found wins.

Layout configuration options

Two layout mechanisms are supported:

  • layout_entries (structured, recommended)
  • layout_template (string template)

You may use either or both, but layout_template takes precedence if defined.

layout_entries

layout_entries defines a structured path builder.

Example:

__meta__:
  layout_entries:
    - key: Study.ID
      entry: study
      sep: "/"
    - key: Subject.ID
      entry: sub
      sep: "/"
    - key: Session
      entry: ses
      sep: "/"
    - key: Modality
      hide: true

Each entry supports:

  • key
    • metadata field name
    • dotted keys are supported
  • entry
    • path label (for example sub, ses, run)
    • omitted entries are skipped
  • sep
    • separator appended after the entry
    • usually / or _
  • hide
    • if true, the key is not rendered
    • still available for template or downstream logic

Resulting path example

Given metadata:

{
  "Study": {"ID": "001"},
  "Subject": {"ID": "003"},
  "Session": "baseline",
  "Modality": "T1w"
}

Result (Modality hide: true only omits the entry label, not the value):

study-001/sub-003/ses-baseline/T1w

Example (missing values are skipped; common when a spec does not emit Modality):

{
  "Study": {"ID": "001"},
  "Subject": {"ID": "003"},
  "Session": "baseline"
}

Result:

study-001/sub-003/ses-baseline/

layout_template

layout_template defines a full path as a format string.

Example:

__meta__:
  layout_template: "study-{Study.ID}/sub-{Subject.ID}/ses-{Session}/{Modality}"

Rules:

  • {Key} placeholders are replaced with metadata values
  • missing keys raise an error unless a default exists upstream
  • template overrides layout_entries entirely

Use templates when:

  • strict compatibility is required
  • external standards mandate exact paths

Fixed keys

Some placeholders are always available, even if they are not present in mapped metadata. These are referred to as fixed keys.

  • {ScanID} / {scan_id} / {scanid}: current scan id.
  • {RecoID} / {reco_id} / {recoid}: current reconstruction id (may be empty when not applicable).
  • {Counter} / {counter}: optional run-local counter for de-duplication (used by brkraw convert --dedupe).

These fixed keys work in both:

  • layout_template placeholders
  • layout_entries via key: ScanID / key: RecoID / key: Counter

slicepack suffix

For multi-slicepack acquisitions, an optional suffix may be applied.

__meta__:
  slicepack_suffix: "_sl{index}"
  • {index} is 1-based
  • appended to filenames, not directories
  • applied only when slicepacks are present

Interaction with context maps

Context maps may define layout metadata:

__meta__:
  layout_entries: ...
  layout_template: ...

Important rules:

  • context-map layout applies only for that run
  • it does not persist or modify global config
  • layout metadata does not affect mapping rules

Filename construction

Layouts define directory structure. Filenames are built from:

  • scan ID
  • reco ID
  • modality or protocol fields
  • slicepack suffix (if applicable)

Exact filename patterns are controlled by:

  • layout configuration
  • converter behavior
  • selected converter hook (if any)

Error handling

Layout evaluation fails if:

  • a required key is missing
  • a template placeholder cannot be resolved
  • metadata contains invalid path characters

Errors are raised before any files are written.

Best practices

  • Prefer layout_entries for readability and composability
  • Use layout_template only when exact paths are required
  • Keep specs free of layout logic
  • Use context maps for project-specific naming
  • Avoid embedding scan IDs directly into specs