[MISC] Generalize rules that labels must be used consistently

src/04-modality-specific-files/01-magnetic-resonance-imaging-data.md

@@ -590,7 +590,7 @@ MUST be used to distinguish both images.
 In such a case, two files could have the following names:
 `sub-01_acq-singleband_dwi.nii.gz` and `sub-01_acq-multiband_dwi.nii.gz`.
 The user is free to choose any other label than `singleband` and
-`multiband`, as long as they are consistent across subjects and sessions.
+`multiband`.
 
 ### REQUIRED gradient orientation information
 

src/04-modality-specific-files/07-behavioral-experiments.md

@@ -24,7 +24,6 @@ rather than `_events.tsv`.
 Each task has a unique label that MUST only consist of letters and/or numbers
 (other characters, including spaces and underscores, are not allowed) with the
 [`task-<label>`](../appendices/entities.md#task) entity.
-Those labels MUST be consistent across subjects and sessions.
 
 The OPTIONAL [`acq-<label>`](../appendices/entities.md#acq) entity corresponds to a custom label to
 distinguish different conditions present during multiple runs of the same task.

src/04-modality-specific-files/09-positron-emission-tomography.md

@@ -80,7 +80,6 @@ Volumes MUST be stored in chronological order (the order they were acquired in).
 
 The OPTIONAL [`task-<label>`](../appendices/entities.md#task) is used to
 indicate a task subjects were asked to perform in the scanner.
-Those labels MUST be consistent across subjects and sessions.
 For task based PET, a corresponding [`task events`](./05-task-events.md) file MUST be provided
 (please note that this file is not necessary for resting scans).
 
@@ -91,8 +90,6 @@ but REQUIRED to distinguish between tracers if multiple are used.
 The label used is arbitrary and each file requires a separate JSON sidecar
 with details of the tracer used (see below).
 Examples are `trc-18FFDG` for fludeoxyglucose or `trc-11CPIB` for Pittsburgh compound B.
-Other labels are permitted, as long as they are consistent across subjects and sessions
-and consist only of the legal label characters.
 
 If more than one run of the same task and acquisition (tracer) are acquired during
 the same session, the [`run-<index>`](../appendices/entities.md#run) entity MUST be used:

src/04-modality-specific-files/10-microscopy.md

@@ -102,7 +102,8 @@ Consistent with other data types in BIDS, the session entity is optional.
 
 The [`sample-<label>`](../appendices/entities.md#sample) entity is REQUIRED for
 Microscopy data and is used to distinguish between different samples from the same subject.
-The label MUST be unique per subject and is RECOMMENDED to be unique throughout the dataset.
+Contrary to other labels, the `sample-<label>` MUST be unique per subject
+and is RECOMMENDED to be unique throughout the dataset.
 
 For example: Three brain slices (`sample-01` to `sample-03`) extracted from subject `sub-01`,
 imaged by scanning electron microscopy (SEM) in PNG format
@@ -133,8 +134,7 @@ MAY be used to distinguish a different set of parameters used for acquiring the
 For example, two images of the same sample acquired by bright-field microscopy (BF) in PNG format at
 different magnification of 40x and 60x.
 In such case two files could have the following names: `sub-01_sample-01_acq-40x_BF.png` and
-`sub-01_sample-01_acq-60x_BF.png`, however the user is free to choose any other label as long as
-they are consistent across subjects and sessions.
+`sub-01_sample-01_acq-60x_BF.png`.
 
 The [`stain-<label>`](../appendices/entities.md#stain) entity MAY be used to distinguish
 image files from the same sample using different stains or antibodies for contrast enhancement.

src/schema/objects/common_principles.yaml

@@ -93,6 +93,9 @@ label:
     for example, it is `rest` in `task-rest` following `task-<label>` specification.
     Note that labels MUST not collide when casing is ignored
     (see [Case collision intolerance](SPEC_ROOT/02-common-principles.md#case-collision-intolerance)).
+    For a given data type, labels MUST be consistent across subjects and sessions.
+    For example, an `acq` entity label `hires` used on the `anat` data of a given subject
+    MUST mean the same thing as `acq-hires` in `anat` files of any other subject.
 modality:
   name: Modality
   display_name: Modality

src/schema/objects/entities.yaml

@@ -13,9 +13,7 @@ acquisition:
     For example, this should be used when a study includes two T1w images -
     one full brain low resolution and one restricted field of view but high resolution.
     In such case two files could have the following names:
-    `sub-01_acq-highres_T1w.nii.gz` and `sub-01_acq-lowres_T1w.nii.gz`;
-    however, the user is free to choose any other label than `highres` and `lowres` as long
-    as they are consistent across subjects and sessions.
+    `sub-01_acq-highres_T1w.nii.gz` and `sub-01_acq-lowres_T1w.nii.gz`.
 
     In case different sequences are used to record the same modality
     (for example, `RARE` and `FLASH` for T1w)
@@ -381,8 +379,6 @@ task:
     a given task may have different sets of stimuli (for example, randomized order) and participant responses
     across subjects, sessions, and runs.
 
-    The `task-<label>` MUST be consistent across subjects and sessions.
-
     Files with the `task-<label>` entity SHOULD have an associated
     [events file](SPEC_ROOT/04-modality-specific-files/05-task-events.md#task-events),
     as well as certain metadata fields in the associated JSON file.