diff --git a/stac_model/examples.py b/stac_model/examples.py
index 9747086..aaeefa5 100644
--- a/stac_model/examples.py
+++ b/stac_model/examples.py
@@ -1,6 +1,9 @@
 import pystac
 import json
 import shapely
+from dateutil.parser import parse as parse_dt
+from pystac import media_type
+
 from stac_model.base import ProcessingExpression
 from stac_model.input import ModelInput
 from stac_model.output import ModelOutput, ModelResult
@@ -86,20 +89,6 @@ def eurosat_resnet() -> MLModelExtension[pystac.Item]:
             expression="torchgeo.datamodules.eurosat.EuroSATDataModule.collate_fn"
         ),  # noqa: E501
     )
-    # runtime = Runtime(
-    #     framework="torch",
-    #     version="2.1.2+cu121",
-    #     asset=Asset(title = "Pytorch weights checkpoint", description="A Resnet-18 classification model trained on normalized Sentinel-2 imagery with Eurosat landcover labels with torchgeo", # noqa: E501
-    #         type=".pth", roles=["weights"], href="https://huggingface.co/torchgeo/resnet18_sentinel2_all_moco/resolve/main/resnet18_sentinel2_all_moco-59bfdff9.pth" # noqa: E501
-    #     ),
-    #     source_code=Asset(
-    #         href="https://github.com/microsoft/torchgeo/blob/61efd2e2c4df7ebe3bd03002ebbaeaa3cfe9885a/torchgeo/models/resnet.py#L207"  # noqa: E501
-    #     ),
-    #     accelerator="cuda",
-    #     accelerator_constrained=False,
-    #     hardware_summary="Unknown",
-    #     commit_hash="61efd2e2c4df7ebe3bd03002ebbaeaa3cfe9885a",
-    # )
     result_array = ModelResult(
         shape=[-1, 10],
         dim_order=["batch", "class"],
@@ -128,11 +117,38 @@ def eurosat_resnet() -> MLModelExtension[pystac.Item]:
         result=result_array,
         post_processing_function=None,
     )
+    assets = {
+        "model": pystac.Asset(
+            title="Pytorch weights checkpoint",
+            description=(
+                "A Resnet-18 classification model trained on normalized Sentinel-2 "
+                "imagery with Eurosat landcover labels with torchgeo."
+            ),
+            href="https://huggingface.co/torchgeo/resnet18_sentinel2_all_moco/resolve/main/resnet18_sentinel2_all_moco-59bfdff9.pth",
+            media_type="application/octet-stream; application=pytorch",
+            roles=[
+                "mlm:model",
+                "mlm:weights",
+                "data"
+            ]
+        ),
+        "source_code": pystac.Asset(
+            href="https://github.com/microsoft/torchgeo/blob/61efd2e2c4df7ebe3bd03002ebbaeaa3cfe9885a/torchgeo/models/resnet.py#L207",
+            media_type="text/x-python",
+            roles=[
+                "mlm:model",
+                "code"
+            ]
+        )
+    }
     ml_model_meta = MLModelProperties(
         name="Resnet-18 Sentinel-2 ALL MOCO",
         tasks={"classification"},
         framework="pytorch",
         framework_version="2.1.2+cu121",
+        accelerator="cuda",
+        accelerator_constrained=False,
+        accelerator_summary="Unknown",
         file_size=43000000,
         memory_size=1,
         pretrained_source="EuroSat Sentinel-2",
@@ -144,7 +160,7 @@ def eurosat_resnet() -> MLModelExtension[pystac.Item]:
     # in docs. start_datetime=datetime.strptime("1900-01-01", "%Y-%m-%d")
     # Is this a problem that we don't do date validation if we supply as str?
     start_datetime = "1900-01-01"
-    end_datetime = None
+    end_datetime = "9999-01-01"  # cannot be None, invalid against STAC Core!
     bbox = [
         -7.882190080512502,
         37.13739173208318,
@@ -159,13 +175,14 @@ def eurosat_resnet() -> MLModelExtension[pystac.Item]:
         bbox=bbox,
         datetime=None,
         properties={
-            "start_datetime": start_datetime,
-            "end_datetime": end_datetime,
+            "start_datetime": parse_dt(start_datetime).isoformat() + "Z",
+            "end_datetime": parse_dt(end_datetime).isoformat() + "Z",
             "description": (
                 "Sourced from torchgeo python library,"
                 "identifier is ResNet18_Weights.SENTINEL2_ALL_MOCO"
             ),
         },
+        assets=assets,
     )
     item.add_derived_from(
         "https://earth-search.aws.element84.com/v1/collections/sentinel-2-l2a"
diff --git a/stac_model/runtime.py b/stac_model/runtime.py
index c0a685b..bf38313 100644
--- a/stac_model/runtime.py
+++ b/stac_model/runtime.py
@@ -1,5 +1,5 @@
 from enum import Enum
-from typing import List, Optional
+from typing import List, Literal, Optional, Union
 
 from pydantic import AnyUrl, BaseModel, ConfigDict, FilePath, Field
 
@@ -40,6 +40,19 @@ def __str__(self):
         return self.value
 
 
+AcceleratorName = Literal[
+    "amd64",
+    "cuda",
+    "xla",
+    "amd-rocm",
+    "intel-ipex-cpu",
+    "intel-ipex-gpu",
+    "macos-arm",
+]
+
+AcceleratorType = Union[AcceleratorName, AcceleratorEnum]
+
+
 class Runtime(BaseModel):
     framework: str = Field(default="", exclude_defaults=True, exclude_unset=True)
     framework_version: str = Field(default="", exclude_defaults=True, exclude_unset=True)
@@ -47,7 +60,7 @@ class Runtime(BaseModel):
     memory_size: int = Field(default=0, exclude_defaults=True, exclude_unset=True)
     batch_size_suggestion: Optional[int] = Field(default=None, exclude_defaults=True, exclude_unset=True)
 
-    accelerator: Optional[AcceleratorEnum] = Field(exclude_unset=True, default=None)
+    accelerator: Optional[AcceleratorType] = Field(exclude_unset=True, default=None)
     accelerator_constrained: bool = Field(exclude_unset=True, default=False)
     accelerator_summary: str = Field(exclude_unset=True, exclude_defaults=True, default="")
     accelerator_count: int = Field(minimum=1, exclude_unset=True, exclude_defaults=True, default=-1)
diff --git a/tests/test_schema.py b/tests/test_schema.py
index b21b0e2..e720cc7 100644
--- a/tests/test_schema.py
+++ b/tests/test_schema.py
@@ -31,3 +31,9 @@ def test_model_metadata_to_dict(eurosat_resnet):
 
 def test_validate_model_metadata(eurosat_resnet):
     assert pystac.read_dict(eurosat_resnet.item.to_dict())
+
+
+def test_validate_model_against_schema(eurosat_resnet, mlm_validator):
+    mlm_item = pystac.read_dict(eurosat_resnet.item.to_dict())
+    validated = pystac.validation.validate(mlm_item, validator=mlm_validator)
+    assert SCHEMA_URI in validated