diff --git a/src/wcflow/core.py b/src/wcflow/core.py
index 0458a99..2e27e2e 100644
--- a/src/wcflow/core.py
+++ b/src/wcflow/core.py
@@ -24,6 +24,8 @@ def __init__(
         lag: list[Duration],
         date: list[datetime],
         arg_option: str | None,
+        *,
+        available: bool,
     ):
         self._name = name
 
@@ -52,6 +54,7 @@ def __init__(
         self._lag = lag
         self._date = date
         self._arg_option = arg_option
+        self._available = available
 
     @property
     def name(self) -> str:
@@ -83,6 +86,10 @@ def date(self) -> list[datetime]:
     def arg_option(self) -> str | None:
         return self._arg_option
 
+    @property
+    def available(self) -> bool:
+        return self._available
+
 
 class Data(_DataBase):
     def __init__(
@@ -93,8 +100,10 @@ def __init__(
         lag: list[Duration],
         date: list[datetime],
         arg_option: str | None,
+        *,
+        available: bool,
     ):
-        super().__init__(name, type, src, lag, date, arg_option)
+        super().__init__(name, type, src, lag, date, arg_option, available=available)
         self._task: Task | None = None
 
     def unroll(self, unrolled_task: UnrolledTask) -> Generator[UnrolledData, None, None]:
@@ -139,7 +148,17 @@ class UnrolledData(_DataBase):
 
     @classmethod
     def from_data(cls, data: Data, unrolled_task: UnrolledTask, unrolled_date: datetime):
-        return cls(unrolled_task, unrolled_date, data.name, data.type, data.src, data.lag, data.date, data.arg_option)
+        return cls(
+            unrolled_task,
+            unrolled_date,
+            data.name,
+            data.type,
+            data.src,
+            data.lag,
+            data.date,
+            data.arg_option,
+            available=data.available,
+        )
 
     def __init__(
         self,
@@ -151,8 +170,10 @@ def __init__(
         lag: list[Duration],
         date: list[datetime],
         arg_option: str | None,
+        *,
+        available: bool,
     ):
-        super().__init__(name, type, src, lag, date, arg_option)
+        super().__init__(name, type, src, lag, date, arg_option, available=available)
         self._unrolled_task = unrolled_task
         self._unrolled_date = unrolled_date
 
@@ -659,14 +680,6 @@ def name(self) -> str:
     def cycles(self) -> list[Cycle]:
         return self._cycles
 
-    def is_available_on_init(self, data: UnrolledData) -> bool:
-        """Determines if the data is available on init of the workflow."""
-
-        def equal_check(output: UnrolledData) -> bool:
-            return output.name == data.name and output.unrolled_date == data.unrolled_date
-
-        return len(list(filter(equal_check, self._unrolled_outputs))) == 0
-
     @property
     def unrolled_cycles(self) -> list[UnrolledCycle]:
         return list(self._unrolled_cycles_map.values())
diff --git a/src/wcflow/parsing/_yaml_data_models.py b/src/wcflow/parsing/_yaml_data_models.py
index 3a2cf9f..551cf31 100644
--- a/src/wcflow/parsing/_yaml_data_models.py
+++ b/src/wcflow/parsing/_yaml_data_models.py
@@ -114,7 +114,7 @@ def convert_to_struct_time(cls, value: str | None) -> time.struct_time | None:
         return None if value is None else time.strptime(value, "%H:%M:%S")
 
 
-class ConfigData(_NamedBaseModel):
+class _DataBaseModel(_NamedBaseModel):
     """
     To create an instance of a data defined in a workflow file.
     """
@@ -132,6 +132,23 @@ def is_file_or_dir(cls, value: str) -> str:
             raise ValueError(msg)
         return value
 
+    @property
+    def available(self) -> bool:
+        return isinstance(self, ConfigAvailableData)
+
+
+class ConfigAvailableData(_DataBaseModel):
+    pass
+
+
+class ConfigGeneratedData(_DataBaseModel):
+    pass
+
+
+class ConfigData(BaseModel):
+    available: list[ConfigAvailableData]
+    generated: list[ConfigGeneratedData]
+
 
 class ConfigCycleTaskDepend(_NamedBaseModel, _LagDateBaseModel):
     """
@@ -257,7 +274,7 @@ class ConfigWorkflow(BaseModel):
     end_date: datetime
     cycles: list[ConfigCycle]
     tasks: list[ConfigTask]
-    data: list[ConfigData]
+    data: ConfigData
     data_dict: dict = {}
     task_dict: dict = {}
 
@@ -274,7 +291,9 @@ def check_start_date_before_end_date(self) -> ConfigWorkflow:
         return self
 
     def to_core_workflow(self):
-        self.data_dict = {data.name: data for data in self.data}
+        self.data_dict = {data.name: data for data in self.data.available} | {
+            data.name: data for data in self.data.generated
+        }
         self.task_dict = {task.name: task for task in self.tasks}
 
         core_cycles = [self._to_core_cycle(cycle) for cycle in self.cycles]
@@ -295,14 +314,16 @@ def _to_core_task(self, cycle_task: ConfigCycleTask) -> core.Task:
             if (data := self.data_dict.get(input_.name)) is None:
                 msg = f"Task {cycle_task.name!r} has input {input_.name!r} that is not specied in the data section."
                 raise ValueError(msg)
-            core_data = core.Data(input_.name, data.type, data.src, input_.lag, input_.date, input_.arg_option)
+            core_data = core.Data(
+                input_.name, data.type, data.src, input_.lag, input_.date, input_.arg_option, available=data.available
+            )
             inputs.append(core_data)
 
         for output in cycle_task.outputs:
             if (data := self.data_dict.get(output.name)) is None:
                 msg = f"Task {cycle_task.name!r} has output {output.name!r} that is not specied in the data section."
                 raise ValueError(msg)
-            core_data = core.Data(output.name, data.type, data.src, [], [], None)
+            core_data = core.Data(output.name, data.type, data.src, [], [], None, available=False)
             outputs.append(core_data)
 
         for depend in cycle_task.depends:
diff --git a/tests/files/configs/test_config_large.yml b/tests/files/configs/test_config_large.yml
index c05a70a..6322339 100644
--- a/tests/files/configs/test_config_large.yml
+++ b/tests/files/configs/test_config_large.yml
@@ -133,43 +133,42 @@ tasks:
       nodes: 1
       walltime: 00:01:00
 data:
-  - preproc_output:
-      type: file
-      src: $PWD/examples/files/data/file.ncdf
-  - grid_file:
-      type: file
-      src: $PWD/examples/files/data/grid
-  - obs_data:
-      type: file
-      src: $PWD/examples/files/data/obs_data
-  - ERA5:
-      type: file
-      src: $PWD/examples/files/data/era5
-  - extpar_file:
-      type: file
-      src: output
-  - icon_input:
-      type: file
-      src: output
-  - icon_restart:
-      type: file
-      format: ncdf
-      src: restart
-  - stream_1:
-      type: file
-      src: output_1
-  - stream_2:
-      type: file
-      src: output_2
-  - postout_1:
-      type: file
-      src: postout
-  - postout_2:
-      type: file
-      src: postout
-  - stored_data_1:
-      type: file
-      src: stored_data
-  - stored_data_2:
-      type: file
-      src: stored_data
+  available:
+    - grid_file:
+        type: file
+        src: $PWD/examples/files/data/grid
+    - obs_data:
+        type: file
+        src: $PWD/examples/files/data/obs_data
+    - ERA5:
+        type: file
+        src: $PWD/examples/files/data/era5
+  generated:
+    - extpar_file:
+        type: file
+        src: output
+    - icon_input:
+        type: file
+        src: output
+    - icon_restart:
+        type: file
+        format: ncdf
+        src: restart
+    - stream_1:
+        type: file
+        src: output_1
+    - stream_2:
+        type: file
+        src: output_2
+    - postout_1:
+        type: file
+        src: postout
+    - postout_2:
+        type: file
+        src: postout
+    - stored_data_1:
+        type: file
+        src: stored_data
+    - stored_data_2:
+        type: file
+        src: stored_data
diff --git a/tests/files/configs/test_config_small.yml b/tests/files/configs/test_config_small.yml
index cb7e2ef..fe06be9 100644
--- a/tests/files/configs/test_config_small.yml
+++ b/tests/files/configs/test_config_small.yml
@@ -23,19 +23,18 @@ tasks:
   - icon:
       plugin: shell
       command: $PWD/tests/files/scripts/icon.py
-  - postproc:
-      plugin: shell
-      command: $PWD/tests/files/scripts/postproc.py
   - cleanup:
       plugin: shell
       command: $PWD/tests/files/scripts/cleanup.py
 data:
-  - icon_input:
-      type: file
-      src: $PWD/tests/files/data/input
-  - icon_output:
-      type: file
-      src: output
-  - icon_restart:
-      type: file
-      src: restart
+  available:
+     - icon_input:
+         type: file
+         src: $PWD/tests/files/data/input
+  generated:
+     - icon_output:
+         type: file
+         src: output
+     - icon_restart:
+         type: file
+         src: restart