diff --git a/src/metaschema.json b/src/metaschema.json
index e5d4c7b400..49d0f8cab7 100644
--- a/src/metaschema.json
+++ b/src/metaschema.json
@@ -71,6 +71,9 @@
             "additionalProperties": false
           }
         },
+        "templates": {
+          "type": "object"
+        },
         "versions": {
           "type": "array",
           "items": {
diff --git a/src/schema/README.md b/src/schema/README.md
index 3505ea1b04..075151f476 100644
--- a/src/schema/README.md
+++ b/src/schema/README.md
@@ -167,21 +167,43 @@ references (the cases in which they are used will be presented later):
     (which are in turn references to individual values), and the references inside `GeneticLevel.anyOf` indicate that there may be a single
     such value or a list of values.
 
-1.  In [`rules.files.deriv.preprocessed_data`][preprocessed_data]:
+1.  In [`rules.files.deriv.imaging`](./rules/files/deriv/imaging.yaml):
     ```YAML
-    anat_nonparametric_common:
-      $ref: rules.files.raw.anat.nonparametric
+    anat_parametric_volumetric:
+      $ref: rules.files.raw.anat.parametric
       entities:
-        $ref: rules.files.raw.anat.nonparametric.entities
-        space: optional
-        description: optional
+        $ref:
+          - meta.templates.deriv.volumetric.entities
+          - rules.files.raw.anat.parametric.entities
     ```
     Here, the derivative datatype rule starts by copying the raw datatype rule
     `rules.files.raw.anat.nonparametric`.
     It then *overrides* the `entities` portion of that rule with a new object.
-    To *extend* the original `entities`, it again begins
-    by referencing `rules.files.raw.anat.nonparametric.entities`,
-    and adding the new entities `space` and `description`.
+    To *extend* the original `entities`, it composes
+    `meta.templates.deriv.volumetric.entities`
+    and `rules.files.raw.anat.nonparametric.entities`.
+    When multiple references are aggregated, the first reference takes
+    precedence.
+
+    Note also that `value: null` can be used to "delete" a key from a template.
+    For example, in `rules.files.raw.events`:
+
+    ```YAML
+    events__pet:
+      $ref: rules.files.raw.events.events
+      datatypes:
+        - pet
+      entities:
+        $ref: meta.templates.raw.task.entities
+        tracer: optional
+        reconstruction: optional
+        # Most events allow acquisition, PET doesn't
+        acquisition: null
+    ```
+
+    This technique should be used judiciously, preferring semantic clarity to brevity.
+    Templates should be expected to grow as BIDS evolves,
+    and should thus be used only where those changes should propagate.
 
 ### Expressions
 
@@ -1071,5 +1093,4 @@ ensuring consistency across the entire schema directory. Validation of the schem
 incorporated into the CI, so any changes that are inconsistent will be flagged before
 inclusion.
 
-[preprocessed_data]: https://github.com/bids-standard/bids-specification/tree/master/src/schema/rules/files/deriv/preprocessed_data.yaml
 [tabular files]: https://bids-specification.readthedocs.io/en/stable/common-principles.html#tabular-files
diff --git a/src/schema/meta/templates.yaml b/src/schema/meta/templates.yaml
new file mode 100644
index 0000000000..f9db50d33d
--- /dev/null
+++ b/src/schema/meta/templates.yaml
@@ -0,0 +1,148 @@
+---
+# This section is unstructured, for inclusion in rules by reference
+
+# Entities that apply to most raw files
+# Include thus:
+#
+# filerule:
+#   entities:
+#     $ref: meta.templates.raw.base.entities
+#     task: optional
+#     ...
+#   datatypes:
+#     ...
+raw:
+  base:
+    entities:
+      subject: required
+      session: optional
+
+  recording:
+    entities:
+      $ref: meta.templates.raw.base.entities
+      acquisition: optional
+      run: optional
+
+  task:
+    entities:
+      $ref: meta.templates.raw.recording.entities
+      task: required
+
+  mri:
+    entities:
+      $ref: meta.templates.raw.recording.entities
+      ceagent: optional
+      reconstruction: optional
+      chunk: optional
+
+  epi:
+    entities:
+      $ref: meta.templates.raw.mri.entities
+      direction: optional
+      part: optional
+
+  pet:
+    entities:
+      $ref: meta.templates.raw.base.entities
+      task: optional
+      tracer: optional
+      reconstruction: optional
+      run: optional
+
+  mrs:
+    entities:
+      $ref: meta.templates.raw.recording.entities
+      task: optional
+      nucleus: optional
+      volume: optional
+      reconstruction: optional
+
+# Entities that apply to most derivative files
+# Include thus:
+#
+# filerule:
+#   entities:
+#     $ref: meta.templates.deriv.base.entities
+#     task: optional
+#     ...
+#   datatypes:
+#     ...
+deriv:
+  base:
+    selectors:
+      - dataset.dataset_description.DatasetType == 'derivative'
+    entities:
+      subject: optional
+      session: optional
+      description: optional
+
+  spatial:
+    $ref: meta.templates.deriv.base
+    entities:
+      $ref: meta.templates.deriv.base.entities
+      space: optional
+
+  # Imaging derivatives
+  volumetric:
+    $ref: meta.templates.deriv.spatial
+    extensions:
+      - .nii.gz
+      - .nii
+      - .json
+    entities:
+      $ref: meta.templates.deriv.spatial.entities
+      resolution: optional
+
+  surface:
+    $ref: meta.templates.deriv.spatial
+    entities:
+      $ref: meta.templates.deriv.spatial.entities
+      hemisphere: optional
+      density: optional
+
+  mask:
+    $ref: meta.templates.deriv.volumetric
+    suffixes:
+      - mask
+    entities:
+      $ref: meta.templates.deriv.volumetric.entities
+      label: optional
+
+  dseg:
+    $ref: meta.templates.deriv.volumetric
+    extensions:
+      - .nii.gz
+      - .nii
+      - .tsv
+      - .json
+    suffixes:
+      - dseg
+    entities:
+      $ref: meta.templates.deriv.volumetric.entities
+      segmentation: optional
+
+  probseg:
+    $ref: meta.templates.deriv.volumetric
+    extensions:
+      - .nii.gz
+      - .nii
+      - .json
+    suffixes:
+      - probseg
+    entities:
+      $ref: meta.templates.deriv.volumetric.entities
+      segmentation: optional
+      label: optional
+
+  dseg_surface:
+    $ref: meta.templates.deriv.surface
+    extensions:
+      - .label.gii
+      - .dlabel.nii
+      - .tsv
+      - .json
+    suffixes:
+      - dseg
+    entities:
+      $ref: meta.templates.deriv.surface.entities
+      segmentation: optional
diff --git a/src/schema/rules/files/deriv/imaging.yaml b/src/schema/rules/files/deriv/imaging.yaml
index 819654b4e5..d2ce8a451d 100644
--- a/src/schema/rules/files/deriv/imaging.yaml
+++ b/src/schema/rules/files/deriv/imaging.yaml
@@ -1,280 +1,327 @@
+# This document implements general imaging derivatives.
+#
+# The _volumetric rules cover supersets of files that would be covered by the
+# common derivatives spec, namely, the space and description entities.
 ---
+# Preprocessed and/or resampled volumes
 anat_parametric_volumetric:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.anat.parametric
+  $ref:
+    - meta.templates.deriv.volumetric
+    - rules.files.raw.anat.parametric
   entities:
-    $ref: rules.files.raw.anat.parametric.entities
-    space: optional
-    resolution: optional
-    density: optional
-    description: optional
+    $ref:
+      - meta.templates.deriv.volumetric.entities
+      - rules.files.raw.anat.parametric.entities
 
 anat_nonparametric_volumetric:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.anat.nonparametric
-  entities:
-    $ref: rules.files.raw.anat.nonparametric.entities
-    space: optional
-    resolution: optional
-    density: optional
-    description: optional
-
-dwi_volumetric:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.dwi.dwi
-  entities:
-    $ref: rules.files.raw.dwi.dwi.entities
-    space: optional
-    resolution: optional
-    density: optional
-    description: optional
+  $ref:
+    - meta.templates.deriv.volumetric
+    - rules.files.raw.anat.nonparametric
+  entities:
+    $ref:
+      - meta.templates.deriv.volumetric.entities
+      - rules.files.raw.anat.nonparametric.entities
+
+anat_defacemask_volumetric:
+  $ref:
+    - meta.templates.deriv.volumetric
+    - rules.files.raw.anat.defacemask
+  entities:
+    $ref:
+      - meta.templates.deriv.volumetric.entities
+      - rules.files.raw.anat.defacemask.entities
+
+anat_mese_volumetric:
+  $ref:
+    - meta.templates.deriv.volumetric
+    - rules.files.raw.anat.mese
+  entities:
+    $ref:
+      - meta.templates.deriv.volumetric.entities
+      - rules.files.raw.anat.mese.entities
+
+anat_megre_volumetric:
+  $ref:
+    - meta.templates.deriv.volumetric
+    - rules.files.raw.anat.megre
+  entities:
+    $ref:
+      - meta.templates.deriv.volumetric.entities
+      - rules.files.raw.anat.megre.entities
+
+anat_multiflip_volumetric:
+  $ref:
+    - meta.templates.deriv.volumetric
+    - rules.files.raw.anat.multiflip
+  entities:
+    $ref:
+      - meta.templates.deriv.volumetric.entities
+      - rules.files.raw.anat.multiflip.entities
+
+anat_multiinversion_volumetric:
+  $ref:
+    - meta.templates.deriv.volumetric
+    - rules.files.raw.anat.multiinversion
+  entities:
+    $ref:
+      - meta.templates.deriv.volumetric.entities
+      - rules.files.raw.anat.multiinversion.entities
+
+anat_mp2rage_volumetric:
+  $ref:
+    - meta.templates.deriv.volumetric
+    - rules.files.raw.anat.mp2rage
+  entities:
+    $ref:
+      - meta.templates.deriv.volumetric.entities
+      - rules.files.raw.anat.mp2rage.entities
+
+anat_vfamt_volumetric:
+  $ref:
+    - meta.templates.deriv.volumetric
+    - rules.files.raw.anat.vfamt
+  entities:
+    $ref:
+      - meta.templates.deriv.volumetric.entities
+      - rules.files.raw.anat.vfamt.entities
+
+anat_mtr_volumetric:
+  $ref:
+    - meta.templates.deriv.volumetric
+    - rules.files.raw.anat.mtr
+  entities:
+    $ref:
+      - meta.templates.deriv.volumetric.entities
+      - rules.files.raw.anat.mtr.entities
+
+dwi_dwi_volumetric:
+  $ref:
+    - meta.templates.deriv.volumetric
+    - rules.files.raw.dwi.dwi
+  entities:
+    $ref:
+      - meta.templates.deriv.volumetric.entities
+      - rules.files.raw.dwi.dwi.entities
+
+dwi_sbref_volumetric:
+  $ref:
+    - meta.templates.deriv.volumetric
+    - rules.files.raw.dwi.sbref
+  entities:
+    $ref:
+      - meta.templates.deriv.volumetric.entities
+      - rules.files.raw.dwi.sbref.entities
 
 dwi_scannerderivatives:
-  $ref: rules.files.raw.dwi.ScannerDerivatives
+  $ref:
+    - meta.templates.deriv.volumetric
+    - rules.files.raw.dwi.ScannerDerivatives
   entities:
-    $ref: rules.files.raw.dwi.ScannerDerivatives.entities
-    space: optional
-    resolution: optional
-    density: optional
-    description: optional
+    $ref:
+      - meta.templates.deriv.volumetric.entities
+      - rules.files.raw.dwi.ScannerDerivatives.entities
 
 func_volumetric:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.func.func
-  entities:
-    $ref: rules.files.raw.func.func.entities
-    space: optional
-    resolution: optional
-    density: optional
-    description: optional
-
-anat_parametric_mask:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.anat.parametric
-  suffixes:
-    - mask
-  entities:
-    $ref: rules.files.raw.anat.parametric.entities
-    space: optional
-    resolution: optional
-    label: optional
-    description: optional
-
-anat_nonparametric_mask:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.anat.nonparametric
-  suffixes:
-    - mask
-  entities:
-    $ref: rules.files.raw.anat.nonparametric.entities
-    space: optional
-    resolution: optional
-    label: optional
-    description: optional
+  $ref:
+    - meta.templates.deriv.volumetric
+    - rules.files.raw.func.func
+  entities:
+    $ref:
+      - meta.templates.deriv.volumetric.entities
+      - rules.files.raw.func.func.entities
+
+func_phase_volumetric:
+  $ref:
+    - meta.templates.deriv.volumetric
+    - rules.files.raw.func.phase
+  entities:
+    $ref:
+      - meta.templates.deriv.volumetric.entities
+      - rules.files.raw.func.phase.entities
+
+fmap_fieldmaps_volumetric:
+  $ref:
+    - meta.templates.deriv.volumetric
+    - rules.files.raw.fmap.fieldmaps
+  entities:
+    $ref:
+      - meta.templates.deriv.volumetric.entities
+      - rules.files.raw.fmap.fieldmaps.entities
+
+fmap_pepolar_volumetric:
+  $ref:
+    - meta.templates.deriv.volumetric
+    - rules.files.raw.fmap.pepolar
+  entities:
+    $ref:
+      - meta.templates.deriv.volumetric.entities
+      - rules.files.raw.fmap.pepolar.entities
+
+fmap_pepolar_m0scan:
+  $ref:
+    - meta.templates.deriv.volumetric
+    - rules.files.raw.fmap.pepolar_m0scan
+  entities:
+    $ref:
+      - meta.templates.deriv.volumetric.entities
+      - rules.files.raw.fmap.pepolar.entities
+
+fmap_TB1DAM_volumetric:
+  $ref:
+    - meta.templates.deriv.volumetric
+    - rules.files.raw.fmap.TB1DAM
+  entities:
+    $ref:
+      - meta.templates.deriv.volumetric.entities
+      - rules.files.raw.fmap.TB1DAM.entities
+
+fmap_TB1EPI_volumetric:
+  $ref:
+    - meta.templates.deriv.volumetric
+    - rules.files.raw.fmap.TB1EPI
+  entities:
+    $ref:
+      - meta.templates.deriv.volumetric.entities
+      - rules.files.raw.fmap.TB1EPI.entities
+
+fmap_RFFieldMaps_volumetric:
+  $ref:
+    - meta.templates.deriv.volumetric
+    - rules.files.raw.fmap.RFFieldMaps
+  entities:
+    $ref:
+      - meta.templates.deriv.volumetric.entities
+      - rules.files.raw.fmap.RFFieldMaps.entities
+
+fmap_TB1SRGE_volumetric:
+  $ref:
+    - meta.templates.deriv.volumetric
+    - rules.files.raw.fmap.TB1SRGE
+  entities:
+    $ref:
+      - meta.templates.deriv.volumetric.entities
+      - rules.files.raw.fmap.TB1SRGE.entities
+
+fmap_parametric_volumetric:
+  $ref:
+    - meta.templates.deriv.volumetric
+    - rules.files.raw.fmap.parametric
+  entities:
+    $ref:
+      - meta.templates.deriv.volumetric.entities
+      - rules.files.raw.fmap.parametric.entities
+
+perf_asl_volumetric:
+  $ref:
+    - meta.templates.deriv.volumetric
+    - rules.files.raw.perf.asl
+  entities:
+    $ref:
+      - meta.templates.deriv.volumetric.entities
+      - rules.files.raw.perf.asl.entities
+
+pet_pet_volumetric:
+  $ref:
+    - meta.templates.deriv.volumetric
+    - rules.files.raw.pet.pet
+  entities:
+    $ref:
+      - meta.templates.deriv.volumetric.entities
+      - rules.files.raw.pet.pet.entities
+
+# Masks
+anat_mask:
+  $ref:
+    - meta.templates.deriv.mask
+    - rules.files.raw.anat.nonparametric
+  entities:
+    # The nonparametric entities are a superset of parametric entities,
+    # so no need to duplicate.
+    $ref:
+      - meta.templates.deriv.mask.entities
+      - rules.files.raw.anat.nonparametric.entities
 
 dwi_mask:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.dwi.dwi
-  suffixes:
-    - mask
-  extensions:
-    - .nii.gz
-    - .nii
-    - .json
-  entities:
-    $ref: rules.files.raw.dwi.dwi.entities
-    space: optional
-    resolution: optional
-    label: optional
-    description: optional
+  $ref:
+    - meta.templates.deriv.mask
+    - rules.files.raw.dwi.dwi
+  entities:
+    $ref:
+      - meta.templates.deriv.mask.entities
+      - rules.files.raw.dwi.dwi.entities
 
 func_mask:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.func.func
-  suffixes:
-    - mask
-  entities:
-    $ref: rules.files.raw.func.func.entities
-    space: optional
-    resolution: optional
-    label: optional
-    description: optional
-
-anat_parametric_discrete_segmentation:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.anat.parametric
-  suffixes:
-    - dseg
-  entities:
-    $ref: rules.files.raw.anat.parametric.entities
-    space: optional
-    segmentation: optional
-    resolution: optional
-    description: optional
-  extensions:
-    - .nii.gz
-    - .nii
-    - .json
-    - .tsv
-
-anat_nonparametric_discrete_segmentation:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.anat.nonparametric
-  suffixes:
-    - dseg
-  entities:
-    $ref: rules.files.raw.anat.nonparametric.entities
-    space: optional
-    segmentation: optional
-    resolution: optional
-    description: optional
-  extensions:
-    - .nii.gz
-    - .nii
-    - .json
-    - .tsv
+  $ref:
+    - meta.templates.deriv.mask
+    - rules.files.raw.func.func
+  entities:
+    $ref:
+      - meta.templates.deriv.mask.entities
+      - rules.files.raw.func.func.entities
+
+# Discrete and probabilistic segmentations
+anat_discrete_segmentation:
+  $ref:
+    - meta.templates.deriv.dseg
+    - rules.files.raw.anat.nonparametric
+  entities:
+    # ibid
+    $ref:
+      - meta.templates.deriv.dseg.entities
+      - rules.files.raw.anat.nonparametric.entities
 
 func_discrete_segmentation:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.func.func
-  suffixes:
-    - dseg
-  entities:
-    $ref: rules.files.raw.func.func.entities
-    space: optional
-    segmentation: optional
-    resolution: optional
-    description: optional
-  extensions:
-    - .nii.gz
-    - .nii
-    - .json
-    - .tsv
+  $ref:
+    - meta.templates.deriv.dseg
+    - rules.files.raw.func.func
+  entities:
+    $ref:
+      - meta.templates.deriv.dseg.entities
+      - rules.files.raw.func.func.entities
 
 dwi_discrete_segmentation:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.dwi.dwi
-  suffixes:
-    - dseg
-  entities:
-    $ref: rules.files.raw.dwi.dwi.entities
-    space: optional
-    resolution: optional
-    description: optional
-  extensions:
-    - .nii.gz
-    - .nii
-    - .json
-    - .tsv
-
-anat_parametric_probabilistic_segmentation:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.anat.parametric
-  suffixes:
-    - probseg
-  entities:
-    $ref: rules.files.raw.anat.parametric.entities
-    space: optional
-    segmentation: optional
-    resolution: optional
-    label: optional
-    description: optional
-
-anat_nonparametric_probabilistic_segmentation:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.anat.nonparametric
-  suffixes:
-    - probseg
-  entities:
-    $ref: rules.files.raw.anat.nonparametric.entities
-    space: optional
-    segmentation: optional
-    resolution: optional
-    label: optional
-    description: optional
+  $ref:
+    - meta.templates.deriv.dseg
+    - rules.files.raw.dwi.dwi
+  entities:
+    $ref:
+      - meta.templates.deriv.dseg.entities
+      - rules.files.raw.dwi.dwi.entities
+
+anat_probabilistic_segmentation:
+  $ref:
+    - meta.templates.deriv.probseg
+    - rules.files.raw.anat.nonparametric
+  entities:
+    # ibid
+    $ref:
+      - meta.templates.deriv.probseg.entities
+      - rules.files.raw.anat.nonparametric.entities
 
 func_probabilistic_segmentation:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.func.func
-  suffixes:
-    - probseg
-  entities:
-    $ref: rules.files.raw.func.func.entities
-    space: optional
-    segmentation: optional
-    resolution: optional
-    label: optional
-    description: optional
+  $ref:
+    - meta.templates.deriv.probseg
+    - rules.files.raw.func.func
+  entities:
+    $ref:
+      - meta.templates.deriv.probseg.entities
+      - rules.files.raw.func.func.entities
 
 dwi_probabilistic_segmentation:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.dwi.dwi
-  suffixes:
-    - probseg
-  entities:
-    $ref: rules.files.raw.dwi.dwi.entities
-    space: optional
-    segmentation: optional
-    resolution: optional
-    label: optional
-    description: optional
-  extensions:
-    - .nii.gz
-    - .nii
-    - .json
-
-anat_parametric_discrete_surface:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.anat.parametric
-  suffixes:
-    - dseg
-  extensions:
-    - .label.gii
-    - .dlabel.nii
-    - .json
-    - .tsv
-  entities:
-    $ref: rules.files.raw.anat.parametric.entities
-    hemisphere: optional
-    space: optional
-    segmentation: optional
-    resolution: optional
-    density: optional
-    description: optional
-
-anat_nonparametric_discrete_surface:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.anat.nonparametric
-  suffixes:
-    - dseg
-  extensions:
-    - .label.gii
-    - .dlabel.nii
-    - .json
-    - .tsv
-  entities:
-    $ref: rules.files.raw.anat.nonparametric.entities
-    hemisphere: optional
-    space: optional
-    segmentation: optional
-    resolution: optional
-    density: optional
-    description: optional
+  $ref:
+    - meta.templates.deriv.probseg
+    - rules.files.raw.dwi.dwi
+  entities:
+    $ref:
+      - meta.templates.deriv.probseg.entities
+      - rules.files.raw.dwi.dwi.entities
+
+anat_discrete_surface:
+  $ref:
+    - meta.templates.deriv.dseg_surface
+    - rules.files.raw.anat.nonparametric
+  entities:
+    # ibid
+    $ref:
+      - meta.templates.deriv.dseg_surface.entities
+      - rules.files.raw.anat.nonparametric.entities
diff --git a/src/schema/rules/files/deriv/preprocessed_data.yaml b/src/schema/rules/files/deriv/preprocessed_data.yaml
index 48ca1bccc6..0a1029b348 100644
--- a/src/schema/rules/files/deriv/preprocessed_data.yaml
+++ b/src/schema/rules/files/deriv/preprocessed_data.yaml
@@ -1,378 +1,175 @@
+# This document implements the common derivatives specification,
+# generally adding space and description entities to most raw data.
+#
+# Imaging files are generally omitted, due to redundancy with imaging.yaml
 ---
-anat_nonparametric_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.anat.nonparametric
-  entities:
-    $ref: rules.files.raw.anat.nonparametric.entities
-    space: optional
-    description: optional
-
-anat_parametric_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.anat.parametric
-  entities:
-    $ref: rules.files.raw.anat.parametric.entities
-    space: optional
-    description: optional
-
-anat_defacemask_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.anat.defacemask
-  entities:
-    $ref: rules.files.raw.anat.defacemask.entities
-    space: optional
-    description: optional
-
-anat_megre_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.anat.megre
-  entities:
-    $ref: rules.files.raw.anat.megre.entities
-    space: optional
-    description: optional
-
-anat_mese_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.anat.mese
-  entities:
-    $ref: rules.files.raw.anat.mese.entities
-    space: optional
-    description: optional
-
-anat_multiflip_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.anat.multiflip
-  entities:
-    $ref: rules.files.raw.anat.multiflip.entities
-    space: optional
-    description: optional
-
-anat_multiinversion_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.anat.multiinversion
-  entities:
-    $ref: rules.files.raw.anat.multiinversion.entities
-    space: optional
-    description: optional
-
-anat_mp2rage_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.anat.mp2rage
-  entities:
-    $ref: rules.files.raw.anat.mp2rage.entities
-    space: optional
-    description: optional
-
-anat_vfamt_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.anat.vfamt
-  entities:
-    $ref: rules.files.raw.anat.vfamt.entities
-    space: optional
-    description: optional
-
-anat_mtr_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.anat.mtr
-  entities:
-    $ref: rules.files.raw.anat.mtr.entities
-    space: optional
-    description: optional
-
 beh_noncontinuous_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.beh.noncontinuous
+  $ref:
+    - meta.templates.deriv.base
+    - rules.files.raw.beh.noncontinuous
   entities:
-    $ref: rules.files.raw.beh.noncontinuous.entities
-    space: optional
-    description: optional
+    $ref:
+      - meta.templates.deriv.base.entities
+      - rules.files.raw.beh.noncontinuous.entities
 
 channels_channels_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.channels.channels
+  $ref:
+    - meta.templates.deriv.base
+    - rules.files.raw.channels.channels
   entities:
-    $ref: rules.files.raw.channels.channels.entities
-    description: optional
+    $ref:
+      - meta.templates.deriv.base.entities
+      - rules.files.raw.channels.channels.entities
 
 channels_channels__meg_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.channels.channels__meg
+  $ref:
+    - meta.templates.deriv.base
+    - rules.files.raw.channels.channels__meg
   entities:
-    $ref: rules.files.raw.channels.channels__meg.entities
-    description: optional
+    $ref:
+      - meta.templates.deriv.base.entities
+      - rules.files.raw.channels.channels__meg.entities
 
 channels_channels__motion_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.channels.channels__motion
+  $ref:
+    - meta.templates.deriv.base
+    - rules.files.raw.channels.channels__motion
   entities:
-    $ref: rules.files.raw.channels.channels__motion.entities
-    description: optional
+    $ref:
+      - meta.templates.deriv.base.entities
+      - rules.files.raw.channels.channels__motion.entities
 
 channels_coordsystem_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.channels.coordsystem
+  $ref:
+    - meta.templates.deriv.base
+    - rules.files.raw.channels.coordsystem
   entities:
-    $ref: rules.files.raw.channels.coordsystem.entities
-    description: optional
+    $ref:
+      - meta.templates.deriv.base.entities
+      - rules.files.raw.channels.coordsystem.entities
 
 channels_coordsystem__eeg_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.channels.coordsystem__eeg
+  $ref:
+    - meta.templates.deriv.base
+    - rules.files.raw.channels.coordsystem__eeg
   entities:
-    $ref: rules.files.raw.channels.coordsystem__eeg.entities
-    description: optional
+    $ref:
+      - meta.templates.deriv.base.entities
+      - rules.files.raw.channels.coordsystem__eeg.entities
 
 channels_electrodes_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.channels.electrodes
+  $ref:
+    - meta.templates.deriv.base
+    - rules.files.raw.channels.electrodes
   entities:
-    $ref: rules.files.raw.channels.electrodes.entities
-    description: optional
+    $ref:
+      - meta.templates.deriv.base.entities
+      - rules.files.raw.channels.electrodes.entities
 
 channels_electrodes__meg_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.channels.electrodes__meg
-  entities:
-    $ref: rules.files.raw.channels.electrodes__meg.entities
-    description: optional
-
-channels_electrodes_optodes_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.channels.optodes
-  entities:
-    $ref: rules.files.raw.channels.optodes.entities
-    description: optional
-
-dwi_dwi_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.dwi.dwi
+  $ref:
+    - meta.templates.deriv.base
+    - rules.files.raw.channels.electrodes__meg
   entities:
-    $ref: rules.files.raw.dwi.dwi.entities
-    space: optional
-    description: optional
+    $ref:
+      - meta.templates.deriv.base.entities
+      - rules.files.raw.channels.electrodes__meg.entities
 
-dwi_sbref_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.dwi.sbref
+channels_optodes_common:
+  $ref:
+    - meta.templates.deriv.base
+    - rules.files.raw.channels.optodes
   entities:
-    $ref: rules.files.raw.dwi.sbref.entities
-    space: optional
-    description: optional
+    $ref:
+      - meta.templates.deriv.base.entities
+      - rules.files.raw.channels.optodes.entities
 
 eeg_eeg_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.eeg.eeg
+  $ref:
+    - meta.templates.deriv.spatial
+    - rules.files.raw.eeg.eeg
   entities:
-    $ref: rules.files.raw.eeg.eeg.entities
-    space: optional
-    description: optional
-
-fmap_fieldmaps_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.fmap.fieldmaps
-  entities:
-    $ref: rules.files.raw.fmap.fieldmaps.entities
-    space: optional
-    description: optional
-
-fmap_pepolar_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.fmap.pepolar
-  entities:
-    $ref: rules.files.raw.fmap.pepolar.entities
-    space: optional
-    description: optional
-
-fmap_pepolar_m0scan:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.fmap.pepolar_m0scan
-  entities:
-    $ref: rules.files.raw.fmap.pepolar.entities
-    space: optional
-    description: optional
-
-fmap_TB1DAM_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.fmap.TB1DAM
-  entities:
-    $ref: rules.files.raw.fmap.TB1DAM.entities
-    space: optional
-    description: optional
-
-fmap_TB1EPI_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.fmap.TB1EPI
-  entities:
-    $ref: rules.files.raw.fmap.TB1EPI.entities
-    space: optional
-    description: optional
-
-fmap_RFFieldMaps_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.fmap.RFFieldMaps
-  entities:
-    $ref: rules.files.raw.fmap.RFFieldMaps.entities
-    space: optional
-    description: optional
-
-fmap_TB1SRGE_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.fmap.TB1SRGE
-  entities:
-    $ref: rules.files.raw.fmap.TB1SRGE.entities
-    space: optional
-    description: optional
-
-fmap_parametric_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.fmap.parametric
-  entities:
-    $ref: rules.files.raw.fmap.parametric.entities
-    space: optional
-    description: optional
-
-func_func_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.func.func
-  entities:
-    $ref: rules.files.raw.func.func.entities
-    space: optional
-    description: optional
-
-func_phase_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.func.phase
-  entities:
-    $ref: rules.files.raw.func.phase.entities
-    space: optional
-    description: optional
+    $ref:
+      - meta.templates.deriv.spatial.entities
+      - rules.files.raw.eeg.eeg.entities
 
 ieeg_ieeg_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.ieeg.ieeg
+  $ref:
+    - meta.templates.deriv.spatial
+    - rules.files.raw.ieeg.ieeg
   entities:
-    $ref: rules.files.raw.ieeg.ieeg.entities
-    space: optional
-    description: optional
+    $ref:
+      - meta.templates.deriv.spatial.entities
+      - rules.files.raw.ieeg.ieeg.entities
 
 meg_meg_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.meg.meg
+  $ref:
+    - meta.templates.deriv.spatial
+    - rules.files.raw.meg.meg
   entities:
-    $ref: rules.files.raw.meg.meg.entities
-    space: optional
-    description: optional
+    $ref:
+      - meta.templates.deriv.spatial.entities
+      - rules.files.raw.meg.meg.entities
 
 meg_calibration_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.meg.calibration
+  $ref:
+    - meta.templates.deriv.spatial
+    - rules.files.raw.meg.calibration
   entities:
-    $ref: rules.files.raw.meg.calibration.entities
-    space: optional
-    description: optional
+    $ref:
+      - meta.templates.deriv.spatial.entities
+      - rules.files.raw.meg.calibration.entities
 
 meg_crosstalk_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.meg.crosstalk
+  $ref:
+    - meta.templates.deriv.spatial
+    - rules.files.raw.meg.crosstalk
   entities:
-    $ref: rules.files.raw.meg.crosstalk.entities
-    space: optional
-    description: optional
+    $ref:
+      - meta.templates.deriv.spatial.entities
+      - rules.files.raw.meg.crosstalk.entities
 
 meg_headshape_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.meg.headshape
+  $ref:
+    - meta.templates.deriv.spatial
+    - rules.files.raw.meg.headshape
   entities:
-    $ref: rules.files.raw.meg.headshape.entities
-    space: optional
-    description: optional
+    $ref:
+      - meta.templates.deriv.spatial.entities
+      - rules.files.raw.meg.headshape.entities
 
 meg_markers_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.meg.markers
+  $ref:
+    - meta.templates.deriv.spatial
+    - rules.files.raw.meg.markers
   entities:
-    $ref: rules.files.raw.meg.markers.entities
-    space: optional
-    description: optional
+    $ref:
+      - meta.templates.deriv.spatial.entities
+      - rules.files.raw.meg.markers.entities
 
 micr_microscopy_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.micr.microscopy
-  entities:
-    $ref: rules.files.raw.micr.microscopy.entities
-    space: optional
-    description: optional
-
-perf_asl_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.perf.asl
-  entities:
-    $ref: rules.files.raw.perf.asl.entities
-    space: optional
-    description: optional
-
-pet_pet_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.pet.pet
+  $ref:
+    - meta.templates.deriv.spatial
+    - rules.files.raw.micr.microscopy
   entities:
-    $ref: rules.files.raw.pet.pet.entities
-    space: optional
-    description: optional
+    $ref:
+      - meta.templates.deriv.spatial.entities
+      - rules.files.raw.micr.microscopy.entities
 
 pet_blood_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.pet.blood
+  $ref:
+    - meta.templates.deriv.spatial
+    - rules.files.raw.pet.blood
   entities:
-    $ref: rules.files.raw.pet.blood.entities
-    space: optional
-    description: optional
+    $ref:
+      - meta.templates.deriv.spatial.entities
+      - rules.files.raw.pet.blood.entities
 
 task_events_common:
-  selectors:
-    - dataset.dataset_description.DatasetType == 'derivative'
-  $ref: rules.files.raw.events.events
+  $ref:
+    - meta.templates.deriv.base
+    - rules.files.raw.events.events
   entities:
-    $ref: rules.files.raw.events.events.entities
-    description: optional
+    $ref:
+      - meta.templates.deriv.base.entities
+      - rules.files.raw.events.events.entities
diff --git a/src/schema/rules/files/raw/anat.yaml b/src/schema/rules/files/raw/anat.yaml
index d1b83f17d9..ba751c0253 100644
--- a/src/schema/rules/files/raw/anat.yaml
+++ b/src/schema/rules/files/raw/anat.yaml
@@ -20,16 +20,10 @@ nonparametric:
   datatypes:
     - anat
   entities:
-    subject: required
-    session: optional
+    $ref: meta.templates.raw.mri.entities
     task: optional
-    acquisition: optional
-    ceagent: optional
-    reconstruction: optional
-    run: optional
     echo: optional
     part: optional
-    chunk: optional
 
 parametric:
   suffixes:
@@ -56,14 +50,8 @@ parametric:
   datatypes:
     - anat
   entities:
-    subject: required
-    session: optional
+    $ref: meta.templates.raw.mri.entities
     task: optional
-    acquisition: optional
-    ceagent: optional
-    reconstruction: optional
-    run: optional
-    chunk: optional
 
 defacemask:
   suffixes:
@@ -75,15 +63,9 @@ defacemask:
   datatypes:
     - anat
   entities:
-    subject: required
-    session: optional
+    $ref: meta.templates.raw.mri.entities
     task: optional
-    acquisition: optional
-    ceagent: optional
-    reconstruction: optional
-    run: optional
     modality: optional
-    chunk: optional
 
 megre:
   suffixes:
@@ -95,16 +77,10 @@ megre:
   datatypes:
     - anat
   entities:
-    subject: required
-    session: optional
+    $ref: meta.templates.raw.mri.entities
     task: optional
-    acquisition: optional
-    ceagent: optional
-    reconstruction: optional
-    run: optional
     echo: required
     part: optional
-    chunk: optional
 
 mese:
   suffixes:
@@ -116,17 +92,11 @@ mese:
   datatypes:
     - anat
   entities:
-    subject: required
-    session: optional
+    $ref: meta.templates.raw.mri.entities
     task: optional
-    acquisition: optional
-    ceagent: optional
-    reconstruction: optional
     direction: optional
-    run: optional
     echo: required
     part: optional
-    chunk: optional
 
 multiflip:
   suffixes:
@@ -138,17 +108,11 @@ multiflip:
   datatypes:
     - anat
   entities:
-    subject: required
-    session: optional
+    $ref: meta.templates.raw.mri.entities
     task: optional
-    acquisition: optional
-    ceagent: optional
-    reconstruction: optional
-    run: optional
     echo: optional
     flip: required
     part: optional
-    chunk: optional
 
 multiinversion:
   suffixes:
@@ -160,16 +124,10 @@ multiinversion:
   datatypes:
     - anat
   entities:
-    subject: required
-    session: optional
+    $ref: meta.templates.raw.mri.entities
     task: optional
-    acquisition: optional
-    ceagent: optional
-    reconstruction: optional
-    run: optional
     inversion: required
     part: optional
-    chunk: optional
 
 mp2rage:
   suffixes:
@@ -181,18 +139,12 @@ mp2rage:
   datatypes:
     - anat
   entities:
-    subject: required
-    session: optional
+    $ref: meta.templates.raw.mri.entities
     task: optional
-    acquisition: optional
-    ceagent: optional
-    reconstruction: optional
-    run: optional
     echo: optional
     flip: optional
     inversion: required
     part: optional
-    chunk: optional
 
 vfamt:
   suffixes:
@@ -205,18 +157,12 @@ vfamt:
   datatypes:
     - anat
   entities:
-    subject: required
-    session: optional
+    $ref: meta.templates.raw.mri.entities
     task: optional
-    acquisition: optional
-    ceagent: optional
-    reconstruction: optional
-    run: optional
     echo: optional
     flip: required
     mtransfer: required
     part: optional
-    chunk: optional
 
 mtr:
   suffixes:
@@ -228,13 +174,7 @@ mtr:
   datatypes:
     - anat
   entities:
-    subject: required
-    session: optional
+    $ref: meta.templates.raw.mri.entities
     task: optional
-    acquisition: optional
-    ceagent: optional
-    reconstruction: optional
-    run: optional
     mtransfer: required
     part: optional
-    chunk: optional
diff --git a/src/schema/rules/files/raw/beh.yaml b/src/schema/rules/files/raw/beh.yaml
index 6193015295..df6f9dac06 100644
--- a/src/schema/rules/files/raw/beh.yaml
+++ b/src/schema/rules/files/raw/beh.yaml
@@ -1,6 +1,7 @@
 ---
 # Non-continuous data
 noncontinuous:
+  $ref: meta.templates.raw.task
   suffixes:
     - beh
   extensions:
@@ -8,9 +9,3 @@ noncontinuous:
     - .json
   datatypes:
     - beh
-  entities:
-    subject: required
-    session: optional
-    task: required
-    acquisition: optional
-    run: optional
diff --git a/src/schema/rules/files/raw/channels.yaml b/src/schema/rules/files/raw/channels.yaml
index 6a4358c689..4f2c9e774b 100644
--- a/src/schema/rules/files/raw/channels.yaml
+++ b/src/schema/rules/files/raw/channels.yaml
@@ -1,5 +1,6 @@
 ---
 channels:
+  $ref: meta.templates.raw.task
   suffixes:
     - channels
   extensions:
@@ -9,12 +10,6 @@ channels:
     - eeg
     - ieeg
     - nirs
-  entities:
-    subject: required
-    session: optional
-    task: required
-    acquisition: optional
-    run: optional
 
 # MEG has an additional entity available
 channels__meg:
@@ -43,8 +38,7 @@ coordsystem:
     - meg
     - nirs
   entities:
-    subject: required
-    session: optional
+    $ref: meta.templates.raw.base.entities
     task: optional
     acquisition: optional
 
@@ -68,11 +62,8 @@ electrodes:
     - eeg
     - ieeg
   entities:
-    subject: required
-    session: optional
+    $ref: meta.templates.raw.recording.entities
     task: optional
-    acquisition: optional
-    run: optional
     space: optional
 
 # MEG has an additional entity available
@@ -93,6 +84,5 @@ optodes:
   datatypes:
     - nirs
   entities:
-    subject: required
-    session: optional
+    $ref: meta.templates.raw.base.entities
     acquisition: optional
diff --git a/src/schema/rules/files/raw/dwi.yaml b/src/schema/rules/files/raw/dwi.yaml
index 91319046dc..cc211150a0 100644
--- a/src/schema/rules/files/raw/dwi.yaml
+++ b/src/schema/rules/files/raw/dwi.yaml
@@ -11,14 +11,10 @@ dwi:
   datatypes:
     - dwi
   entities:
-    subject: required
-    session: optional
-    acquisition: optional
-    reconstruction: optional
-    direction: optional
-    run: optional
-    part: optional
-    chunk: optional
+    $ref: meta.templates.raw.epi.entities
+    # Historically BIDS has not permitted ceagent for DWI
+    # This could be relaxed without backwards incompatibility
+    ceagent: null
 
 sbref:
   suffixes:
@@ -30,14 +26,8 @@ sbref:
   datatypes:
     - dwi
   entities:
-    subject: required
-    session: optional
-    acquisition: optional
-    reconstruction: optional
-    direction: optional
-    run: optional
-    part: optional
-    chunk: optional
+    $ref: meta.templates.raw.epi.entities
+    ceagent: null
 
 # Common scanner-generated derivatives need raw names
 ScannerDerivatives:
@@ -55,10 +45,7 @@ ScannerDerivatives:
   datatypes:
     - dwi
   entities:
-    subject: required
-    session: optional
-    acquisition: optional
-    reconstruction: optional
-    direction: optional
-    run: optional
-    chunk: optional
+    $ref: meta.templates.raw.epi.entities
+    # part is also not defined for derivative maps
+    ceagent: null
+    part: null
diff --git a/src/schema/rules/files/raw/eeg.yaml b/src/schema/rules/files/raw/eeg.yaml
index 676d66dc1b..0fa2e21feb 100644
--- a/src/schema/rules/files/raw/eeg.yaml
+++ b/src/schema/rules/files/raw/eeg.yaml
@@ -1,5 +1,6 @@
 ---
 eeg:
+  $ref: meta.templates.raw.task
   suffixes:
     - eeg
   extensions:
@@ -13,9 +14,3 @@ eeg:
     - .bdf
   datatypes:
     - eeg
-  entities:
-    subject: required
-    session: optional
-    task: required
-    acquisition: optional
-    run: optional
diff --git a/src/schema/rules/files/raw/events.yaml b/src/schema/rules/files/raw/events.yaml
index 7800b946df..bbd1ff9b84 100644
--- a/src/schema/rules/files/raw/events.yaml
+++ b/src/schema/rules/files/raw/events.yaml
@@ -1,5 +1,6 @@
 ---
 events:
+  $ref: meta.templates.raw.task
   suffixes:
     - events
   extensions:
@@ -11,12 +12,6 @@ events:
     - ieeg
     - meg
     - nirs
-  entities:
-    subject: required
-    session: optional
-    task: required
-    acquisition: optional
-    run: optional
 
 # Specializations
 # In these rules, we use $ref to retrieve most of an object, and then override
@@ -44,20 +39,11 @@ events__pet:
   datatypes:
     - pet
   entities:
-    # Most events allow acquisition, PET doesn't
-    subject: required
-    session: optional
-    task: required
-    tracer: optional
-    reconstruction: optional
-    run: optional
+    $ref: meta.templates.raw.pet.entities
 
 events__mrs:
   $ref: rules.files.raw.events.events
   datatypes:
     - mrs
   entities:
-    $ref: rules.files.raw.events.events.entities
-    reconstruction: optional
-    nucleus: optional
-    volume: optional
+    $ref: meta.templates.raw.mrs.entities
diff --git a/src/schema/rules/files/raw/fmap.yaml b/src/schema/rules/files/raw/fmap.yaml
index 79d5944feb..7d04c547a4 100644
--- a/src/schema/rules/files/raw/fmap.yaml
+++ b/src/schema/rules/files/raw/fmap.yaml
@@ -15,13 +15,11 @@ fieldmaps:
   datatypes:
     - fmap
   entities:
-    subject: required
-    session: optional
-    acquisition: optional
-    run: optional
+    $ref: meta.templates.raw.recording.entities
     chunk: optional
 
 pepolar:
+  $ref: meta.templates.raw.epi
   suffixes:
     - epi
   extensions:
@@ -32,17 +30,9 @@ pepolar:
     - .bvec
   datatypes:
     - fmap
-  entities:
-    subject: required
-    session: optional
-    acquisition: optional
-    ceagent: optional
-    direction: required
-    run: optional
-    part: optional
-    chunk: optional
 
 pepolar_m0scan:
+  $ref: meta.templates.raw.epi
   suffixes:
     - m0scan
   extensions:
@@ -51,15 +41,6 @@ pepolar_m0scan:
     - .json
   datatypes:
     - fmap
-  entities:
-    subject: required
-    session: optional
-    acquisition: optional
-    ceagent: optional
-    direction: required
-    run: optional
-    part: optional
-    chunk: optional
 
 TB1DAM:
   suffixes:
@@ -71,16 +52,10 @@ TB1DAM:
   datatypes:
     - fmap
   entities:
-    subject: required
-    session: optional
-    acquisition: optional
-    ceagent: optional
-    reconstruction: optional
-    run: optional
+    $ref: meta.templates.raw.mri.entities
     flip: required
     inversion: optional
     part: optional
-    chunk: optional
 
 TB1EPI:
   suffixes:
@@ -92,17 +67,11 @@ TB1EPI:
   datatypes:
     - fmap
   entities:
-    subject: required
-    session: optional
-    acquisition: optional
-    ceagent: optional
-    reconstruction: optional
-    run: optional
+    $ref: meta.templates.raw.mri.entities
     echo: required
     flip: required
     inversion: optional
     part: optional
-    chunk: optional
 
 RFFieldMaps:
   suffixes:
@@ -117,17 +86,11 @@ RFFieldMaps:
   datatypes:
     - fmap
   entities:
-    subject: required
-    session: optional
-    acquisition: optional
-    ceagent: optional
-    reconstruction: optional
-    run: optional
+    $ref: meta.templates.raw.mri.entities
     echo: optional
     flip: optional
     inversion: optional
     part: optional
-    chunk: optional
 
 TB1SRGE:
   suffixes:
@@ -139,19 +102,14 @@ TB1SRGE:
   datatypes:
     - fmap
   entities:
-    subject: required
-    session: optional
-    acquisition: optional
-    ceagent: optional
-    reconstruction: optional
-    run: optional
+    $ref: meta.templates.raw.mri.entities
     echo: optional
     flip: required
     inversion: required
     part: optional
-    chunk: optional
 
 parametric:
+  $ref: meta.templates.raw.mri
   suffixes:
     - TB1map
     - RB1map
@@ -161,11 +119,3 @@ parametric:
     - .json
   datatypes:
     - fmap
-  entities:
-    subject: required
-    session: optional
-    acquisition: optional
-    ceagent: optional
-    reconstruction: optional
-    run: optional
-    chunk: optional
diff --git a/src/schema/rules/files/raw/func.yaml b/src/schema/rules/files/raw/func.yaml
index 61a614bead..4072d04437 100644
--- a/src/schema/rules/files/raw/func.yaml
+++ b/src/schema/rules/files/raw/func.yaml
@@ -11,17 +11,10 @@ func:
   datatypes:
     - func
   entities:
-    subject: required
-    session: optional
-    task: required
-    acquisition: optional
-    ceagent: optional
-    reconstruction: optional
-    direction: optional
-    run: optional
+    $ref:
+      - meta.templates.raw.epi.entities
+      - meta.templates.raw.task.entities
     echo: optional
-    part: optional
-    chunk: optional
 
 norf:
   $ref: rules.files.raw.func.func
@@ -32,22 +25,9 @@ norf:
     modality: optional
 
 phase:
+  $ref: rules.files.raw.func.func
   suffixes:
     - phase # deprecated
-  extensions:
-    - .nii.gz
-    - .nii
-    - .json
-  datatypes:
-    - func
   entities:
-    subject: required
-    session: optional
-    task: required
-    acquisition: optional
-    ceagent: optional
-    reconstruction: optional
-    direction: optional
-    run: optional
-    echo: optional
-    chunk: optional
+    $ref: rules.files.raw.func.func.entities
+    part: null
diff --git a/src/schema/rules/files/raw/ieeg.yaml b/src/schema/rules/files/raw/ieeg.yaml
index 587f9bcbb8..9197aa9676 100644
--- a/src/schema/rules/files/raw/ieeg.yaml
+++ b/src/schema/rules/files/raw/ieeg.yaml
@@ -1,5 +1,6 @@
 ---
 ieeg:
+  $ref: meta.templates.raw.task
   suffixes:
     - ieeg
   extensions:
@@ -14,9 +15,3 @@ ieeg:
     - .nwb
   datatypes:
     - ieeg
-  entities:
-    subject: required
-    session: optional
-    task: required
-    acquisition: optional
-    run: optional
diff --git a/src/schema/rules/files/raw/meg.yaml b/src/schema/rules/files/raw/meg.yaml
index a25ed56646..48de894cdd 100644
--- a/src/schema/rules/files/raw/meg.yaml
+++ b/src/schema/rules/files/raw/meg.yaml
@@ -19,11 +19,7 @@ meg:
   datatypes:
     - meg
   entities:
-    subject: required
-    session: optional
-    task: required
-    acquisition: optional
-    run: optional
+    $ref: meta.templates.raw.task.entities
     processing: optional
     split: optional
 
@@ -35,8 +31,7 @@ calibration:
   datatypes:
     - meg
   entities:
-    subject: required
-    session: optional
+    $ref: meta.templates.raw.base.entities
     acquisition:
       level: required
       enum:
@@ -50,8 +45,7 @@ crosstalk:
   datatypes:
     - meg
   entities:
-    subject: required
-    session: optional
+    $ref: meta.templates.raw.base.entities
     acquisition:
       level: required
       enum:
@@ -66,8 +60,7 @@ headshape:
   datatypes:
     - meg
   entities:
-    subject: required
-    session: optional
+    $ref: meta.templates.raw.base.entities
     acquisition: optional
 
 markers:
@@ -79,8 +72,7 @@ markers:
   datatypes:
     - meg
   entities:
-    subject: required
-    session: optional
+    $ref: meta.templates.raw.base.entities
     task: optional
     acquisition: optional
     space: optional
diff --git a/src/schema/rules/files/raw/micr.yaml b/src/schema/rules/files/raw/micr.yaml
index b256033ce9..ba88843472 100644
--- a/src/schema/rules/files/raw/micr.yaml
+++ b/src/schema/rules/files/raw/micr.yaml
@@ -29,10 +29,7 @@ microscopy:
   datatypes:
     - micr
   entities:
-    subject: required
-    session: optional
+    $ref: meta.templates.raw.recording.entities
     sample: required
-    acquisition: optional
     stain: optional
-    run: optional
     chunk: optional
diff --git a/src/schema/rules/files/raw/motion.yaml b/src/schema/rules/files/raw/motion.yaml
index 5ac18a4e92..818a979792 100644
--- a/src/schema/rules/files/raw/motion.yaml
+++ b/src/schema/rules/files/raw/motion.yaml
@@ -8,9 +8,5 @@ motion:
   datatypes:
     - motion
   entities:
-    subject: required
-    session: optional
-    task: required
+    $ref: meta.templates.raw.task.entities
     tracksys: required
-    acquisition: optional
-    run: optional
diff --git a/src/schema/rules/files/raw/mrs.yaml b/src/schema/rules/files/raw/mrs.yaml
index fe95f08f3a..1190bebbf1 100644
--- a/src/schema/rules/files/raw/mrs.yaml
+++ b/src/schema/rules/files/raw/mrs.yaml
@@ -12,13 +12,6 @@ mrs:
   datatypes:
     - mrs
   entities:
-    subject: required
-    session: optional
-    task: optional
-    acquisition: optional
-    reconstruction: optional
-    run: optional
+    $ref: meta.templates.raw.mrs.entities
     echo: optional
     inversion: optional
-    nucleus: optional
-    volume: optional
diff --git a/src/schema/rules/files/raw/nirs.yaml b/src/schema/rules/files/raw/nirs.yaml
index 8dfc41e861..aafce13fa9 100644
--- a/src/schema/rules/files/raw/nirs.yaml
+++ b/src/schema/rules/files/raw/nirs.yaml
@@ -1,5 +1,6 @@
 ---
 nirs:
+  $ref: meta.templates.raw.task
   suffixes:
     - nirs
   extensions:
@@ -7,9 +8,3 @@ nirs:
     - .json
   datatypes:
     - nirs
-  entities:
-    subject: required
-    session: optional
-    task: required
-    acquisition: optional
-    run: optional
diff --git a/src/schema/rules/files/raw/perf.yaml b/src/schema/rules/files/raw/perf.yaml
index c725bef442..330bdc087a 100644
--- a/src/schema/rules/files/raw/perf.yaml
+++ b/src/schema/rules/files/raw/perf.yaml
@@ -10,14 +10,10 @@ asl:
   datatypes:
     - perf
   entities:
-    subject: required
-    session: optional
-    acquisition: optional
-    reconstruction: optional
-    direction: optional
-    run: optional
+    $ref: meta.templates.raw.epi.entities
     echo: optional
-    part: optional
+    ceagent: null
+    chunk: null
 
 aslcontext:
   suffixes:
@@ -27,12 +23,10 @@ aslcontext:
   datatypes:
     - perf
   entities:
-    subject: required
-    session: optional
-    acquisition: optional
-    reconstruction: optional
-    direction: optional
-    run: optional
+    $ref: meta.templates.raw.epi.entities
+    ceagent: null
+    part: null
+    chunk: null
 
 asllabeling:
   suffixes:
@@ -44,11 +38,8 @@ asllabeling:
   datatypes:
     - perf
   entities:
-    subject: required
-    session: optional
-    acquisition: optional
+    $ref: meta.templates.raw.recording.entities
     reconstruction: optional
-    run: optional
 
 norf:
   $ref: rules.files.raw.perf.asl
diff --git a/src/schema/rules/files/raw/pet.yaml b/src/schema/rules/files/raw/pet.yaml
index a94cb9addd..2f543efac1 100644
--- a/src/schema/rules/files/raw/pet.yaml
+++ b/src/schema/rules/files/raw/pet.yaml
@@ -9,12 +9,7 @@ pet:
   datatypes:
     - pet
   entities:
-    subject: required
-    session: optional
-    task: optional
-    tracer: optional
-    reconstruction: optional
-    run: optional
+    $ref: meta.templates.raw.pet.entities
 
 blood:
   suffixes:
@@ -25,10 +20,5 @@ blood:
   datatypes:
     - pet
   entities:
-    subject: required
-    session: optional
-    task: optional
-    tracer: optional
-    reconstruction: optional
-    run: optional
+    $ref: meta.templates.raw.pet.entities
     recording: required
diff --git a/src/schema/rules/files/raw/photo.yaml b/src/schema/rules/files/raw/photo.yaml
index f5969e2d0c..65706b02d8 100644
--- a/src/schema/rules/files/raw/photo.yaml
+++ b/src/schema/rules/files/raw/photo.yaml
@@ -12,8 +12,7 @@ photo:
     - meg
     - nirs
   entities:
-    subject: required
-    session: optional
+    $ref: meta.templates.raw.base.entities
     acquisition: optional
 
 photo__micr:
diff --git a/src/schema/rules/files/raw/task.yaml b/src/schema/rules/files/raw/task.yaml
index 8a207a7384..15fab309de 100644
--- a/src/schema/rules/files/raw/task.yaml
+++ b/src/schema/rules/files/raw/task.yaml
@@ -12,11 +12,7 @@ timeseries:
     - ieeg
     - nirs
   entities:
-    subject: required
-    session: optional
-    task: required
-    acquisition: optional
-    run: optional
+    $ref: meta.templates.raw.task.entities
     recording: optional
 
 timeseries__mri_no_task:
@@ -30,10 +26,7 @@ timeseries__mri_no_task:
     - dwi
     - perf
   entities:
-    subject: required
-    session: optional
-    acquisition: optional
-    run: optional
+    $ref: meta.templates.raw.recording.entities
     reconstruction: optional
     direction: optional
     recording: optional
@@ -46,12 +39,11 @@ timeseries__anat:
   datatypes:
     - anat
   entities:
-    $ref: rules.files.raw.task.timeseries.entities
-    ceagent: optional
-    reconstruction: optional
+    $ref:
+      - rules.files.raw.task.timeseries.entities
+      - meta.templates.raw.mri.entities
     echo: optional
     part: optional
-    chunk: optional
     modality: optional
 
 timeseries__func:
@@ -85,11 +77,8 @@ timeseries__pet:
   datatypes:
     - pet
   entities:
-    # Most timeseries allow acquisition, PET doesn't
-    subject: required
-    session: optional
-    task: required
+    $ref: rules.files.raw.task.timeseries.entities
     tracer: optional
     reconstruction: optional
-    run: optional
-    recording: optional
+    # Most timeseries allow acquisition, PET doesn't
+    acquisition: null
diff --git a/tools/schemacode/src/bidsschematools/schema.py b/tools/schemacode/src/bidsschematools/schema.py
index ca36e2668b..0208d51e00 100644
--- a/tools/schemacode/src/bidsschematools/schema.py
+++ b/tools/schemacode/src/bidsschematools/schema.py
@@ -5,6 +5,7 @@
 import json
 import os
 import re
+from collections import ChainMap
 from collections.abc import Iterable, Mapping
 from copy import deepcopy
 from functools import cache, lru_cache
@@ -90,17 +91,32 @@ def _find(obj, predicate):
 
 def _dereference(namespace, base_schema):
     # In-place, recursively dereference objects
-    # This allows a referenced object to itself contain a reference
-    # A dependency graph could be constructed, but would likely be slower
-    # to build than to duplicate a couple dereferences
+    # This allows for referencing objects that contain references,
+    # as well as objects that do not exist until a parent is dereferenced.
     for struct in _find(namespace, lambda obj: "$ref" in obj):
-        target = base_schema.get(struct["$ref"])
-        if target is None:
-            raise ValueError(f"Reference {struct['$ref']} not found in schema.")
-        if isinstance(target, Mapping):
+        refs = struct["$ref"]
+        if isinstance(refs, str):
+            refs = [refs]
+        targets = []
+        for ref in refs:
+            target = base_schema
+            for part in ref.split("."):
+                target = target.get(part)
+                if target is None:
+                    raise ValueError(f"Reference {ref} not found in schema.")
+                if "$ref" in target:
+                    _dereference(target, base_schema)
+            targets.append(target)
+
+        if all(isinstance(target, Mapping) for target in targets):
             struct.pop("$ref")
-            _dereference(target, base_schema)
-            struct.update({**target, **struct})
+
+            struct.update({**ChainMap(*targets), **struct})
+
+            # Use `key: null` to delete fields
+            for key, value in list(struct.items()):
+                if value is None:
+                    del struct[key]
 
 
 @cache
diff --git a/tools/schemacode/src/bidsschematools/tests/test_schema.py b/tools/schemacode/src/bidsschematools/tests/test_schema.py
index 3ee2430fe4..0663cec898 100644
--- a/tools/schemacode/src/bidsschematools/tests/test_schema.py
+++ b/tools/schemacode/src/bidsschematools/tests/test_schema.py
@@ -412,18 +412,18 @@ def test_valid_schema_with_check_jsonschema(tmp_path, regex_variant):
 def test_add_legal_field():
     """Test that adding a legal field does not raise an error."""
     namespace = schema.load_schema()
-    namespace["rules"]["files"]["deriv"]["preprocessed_data"]["anat_nonparametric_common"][
-        "entities"
-    ]["density"] = "optional"
+    namespace["rules"]["files"]["deriv"]["imaging"]["anat_nonparametric_volumetric"]["entities"][
+        "density"
+    ] = "optional"
     schema.validate_schema(namespace)
 
 
 def test_invalid_value():
     """Test that an invalid value raises an error."""
     namespace = schema.load_schema()
-    namespace["rules"]["files"]["deriv"]["preprocessed_data"]["anat_nonparametric_common"][
-        "entities"
-    ]["density"] = "invalid"
+    namespace["rules"]["files"]["deriv"]["imaging"]["anat_nonparametric_volumetric"]["entities"][
+        "density"
+    ] = "invalid"
     with pytest.raises(ValidationError) as e:
         schema.validate_schema(namespace)
     print(e.value)