diff --git a/.make b/.make
index c1804ce36f5ce10ca011ad0ccee022fe21e5384e..c38a4d0c11b18a778c6d79ec26029fef22e85155 160000
--- a/.make
+++ b/.make
@@ -1 +1 @@
-Subproject commit c1804ce36f5ce10ca011ad0ccee022fe21e5384e
+Subproject commit c38a4d0c11b18a778c6d79ec26029fef22e85155
diff --git a/src/ska_telmodel/sdp/examples/v1_2_dev.py b/src/ska_telmodel/sdp/examples/v1_2_dev.py
new file mode 100644
index 0000000000000000000000000000000000000000..f126042c82e75b3c9986838a8dbc354181cb20ae
--- /dev/null
+++ b/src/ska_telmodel/sdp/examples/v1_2_dev.py
@@ -0,0 +1,31 @@
+"""SDP schema 1.2 examples."""
+
+import copy
+
+from .v1_1 import SDP_ASSIGNRES as SDP_ASSIGNRES_1_1
+from .v1_1 import (
+    get_sdp_configure,
+    get_sdp_recvaddrs,
+    get_sdp_releaseres,
+    get_sdp_scan,
+)
+
+__all__ = [
+    "get_sdp_assignres",
+    "get_sdp_configure",
+    "get_sdp_scan",
+    "get_sdp_recvaddrs",
+    "get_sdp_releaseres",
+]
+
+SDP_ASSIGNRES = copy.deepcopy(SDP_ASSIGNRES_1_1)
+SDP_ASSIGNRES["execution_block"]["telmodel_sources"] = [
+    "car:ska-low-tmdata?main"
+]
+SDP_ASSIGNRES["execution_block"]["scan_types"][1]["beams"]["vis0"][
+    "integration_time"
+] = 0.125
+
+
+def get_sdp_assignres(version: str):
+    return copy.deepcopy(SDP_ASSIGNRES)
diff --git a/src/ska_telmodel/sdp/schemas/v0_4.py b/src/ska_telmodel/sdp/schemas/v0_4.py
index fe7731b84a6212d932db84824ce3419cb6596967..29a14b4dd83c895e88452c2b163813467c492931 100644
--- a/src/ska_telmodel/sdp/schemas/v0_4.py
+++ b/src/ska_telmodel/sdp/schemas/v0_4.py
@@ -22,6 +22,7 @@ __all__ = [
     "get_sdp_configure",
     "get_sdp_scan",
     "get_sdp_recvaddrs",
+    "get_sdp_releaseres",
 ]
 
 
@@ -169,14 +170,27 @@ def get_execution_block(version: str, strict: bool) -> TMSchema:
         strict,
         schema={
             "eb_id": get_eb_name_schema(version, strict),
-            "max_length": float,
-            Literal(
-                "context",
-                description="Free-form information from OET, see ADR-54",
-            ): Schema(dict),
         },
         as_reference=True,
     )
+    schema.add_field(
+        "max_length",
+        float,
+        description=cleandoc(
+            """
+            Maximum observation length in seconds.
+
+            Used to ensure that enough buffer capacity is available to capture
+            data. Resource assignment might fail if we do not have enough
+            space to guarantee that all data could be captured.
+            """
+        ),
+    )
+    schema.add_field(
+        "context",
+        dict,
+        description="Free-form information from OET, see ADR-54",
+    )
     schema.add_field(
         "beams", [get_beam(version, strict)], description="Beam parameters"
     )
diff --git a/src/ska_telmodel/sdp/schemas/v1_2_dev.py b/src/ska_telmodel/sdp/schemas/v1_2_dev.py
new file mode 100644
index 0000000000000000000000000000000000000000..25332997433dd7c743578483935ac0a8da5cefa7
--- /dev/null
+++ b/src/ska_telmodel/sdp/schemas/v1_2_dev.py
@@ -0,0 +1,90 @@
+"""Version 1.2 of SDP schema"""
+
+from inspect import cleandoc
+
+from ska_telmodel._common import TMSchema
+
+from . import v1_1
+from .v1_1 import (
+    get_sdp_configure,
+    get_sdp_recvaddrs,
+    get_sdp_releaseres,
+    get_sdp_scan,
+)
+
+__all__ = [
+    "get_sdp_assignres",
+    "get_sdp_configure",
+    "get_sdp_scan",
+    "get_sdp_recvaddrs",
+    "get_sdp_releaseres",
+]
+
+
+def get_scan_type_beam(version: str, strict: bool) -> TMSchema:
+    schema = TMSchema.new(
+        "Beam",
+        version,
+        strict,
+    )
+    schema.add_opt_field(
+        "field_id",
+        str,
+        description="Field ID.",
+    )
+    schema.add_opt_field(
+        "channels_id",
+        str,
+        description="Channels ID.",
+    )
+    schema.add_opt_field(
+        "polarisations_id",
+        str,
+        description="Polarisations ID.",
+    )
+    schema.add_opt_field(
+        "integration_time",
+        float,
+        description=cleandoc(
+            """
+            Correlator integration time in seconds.
+
+            Applies to visibility beams only.
+            """
+        ),
+    )
+    return schema
+
+
+def get_sdp_assignres(version: str, strict: bool) -> TMSchema:
+    # Get 1.1 version
+    schema = v1_1.get_sdp_assignres(version, strict)
+
+    # Add Telescope Model data sources to EB
+    exec_block = schema["execution_block"]
+    exec_block.add_opt_field(
+        "telmodel_sources",
+        [str],
+        description=cleandoc(
+            """
+            Telescope model data sources.
+
+            Processing blocks associated with the execution block will use
+            this to look up information about the telescope (such as the
+            telescope layout) for the purpose of processing and generating
+            metadata. The sources should be "pinned" to specific versions to
+            ensure that processing results are repeatable (see `Data Sources
+            <https://developer.skao.int/projects/ska-telmodel/en/latest/ska-telmodel/usage.html#data-sources>`_).
+            """
+        ),
+    )
+
+    # Update beams in scan type
+    scan_type = schema["execution_block"]["scan_types"][0]
+    del scan_type["beams"]
+    scan_type.add_field(
+        "beams",
+        {str: get_scan_type_beam(version, strict)},
+    )
+
+    return schema
diff --git a/src/ska_telmodel/sdp/version.py b/src/ska_telmodel/sdp/version.py
index 27528681983e9e3f024cd17708a3e583ee66e90a..d72315380a658b29c199d1246696f4e9af7eda22 100644
--- a/src/ska_telmodel/sdp/version.py
+++ b/src/ska_telmodel/sdp/version.py
@@ -18,7 +18,7 @@ SDP_INTERFACE_STABLE_VERSIONS = [
     (1, 1),
 ]
 
-SDP_INTERFACE_DEV_VERSIONS = []
+SDP_INTERFACE_DEV_VERSIONS = [(1, 2)]
 
 SDP_INTERFACE_VERSIONS = (
     SDP_INTERFACE_STABLE_VERSIONS + SDP_INTERFACE_DEV_VERSIONS