diff --git a/.idea/dictionaries/dictionary.xml b/.idea/dictionaries/dictionary.xml
index f2d484282..7db7138b1 100644
--- a/.idea/dictionaries/dictionary.xml
+++ b/.idea/dictionaries/dictionary.xml
@@ -2,6 +2,8 @@
   <dictionary name="dictionary">
     <words>
       <w>opentasks</w>
+      <w>subtask</w>
+      <w>subtasks</w>
     </words>
   </dictionary>
 </component>
\ No newline at end of file
diff --git a/gradle.properties b/gradle.properties
index c1dfcd9fe..4c4856618 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -4,5 +4,5 @@ MIN_SDK_VERSION=9
 TARGET_SDK_VERSION=25
 # dependency versions
 SUPPORT_LIBRARY_VERSION=25.0.1
-CONTENTPAL_VERSION=879bb47
+CONTENTPAL_VERSION=2d16bb5
 ROBOLECTRIC_VERSION=3.1.4
\ No newline at end of file
diff --git a/opentaskspal/src/main/java/org/dmfs/opentaskspal/operations/SubtaskRelation.java b/opentaskspal/src/main/java/org/dmfs/opentaskspal/operations/SubtaskRelation.java
new file mode 100644
index 000000000..ec7375575
--- /dev/null
+++ b/opentaskspal/src/main/java/org/dmfs/opentaskspal/operations/SubtaskRelation.java
@@ -0,0 +1,65 @@
+/*
+ * Copyright 2017 dmfs GmbH
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.dmfs.opentaskspal.operations;
+
+import android.content.ContentProviderOperation;
+import android.support.annotation.NonNull;
+
+import org.dmfs.android.contentpal.InsertOperation;
+import org.dmfs.android.contentpal.Operation;
+import org.dmfs.android.contentpal.RowSnapshot;
+import org.dmfs.android.contentpal.SoftRowReference;
+import org.dmfs.android.contentpal.TransactionContext;
+import org.dmfs.android.contentpal.operations.Insert;
+import org.dmfs.opentaskspal.tables.PropertiesTable;
+import org.dmfs.opentaskspal.tasks.ParentTaskRelationData;
+import org.dmfs.optional.Optional;
+import org.dmfs.tasks.contract.TaskContract;
+
+
+/**
+ * {@link InsertOperation} for adding a 'subtask relation' property to {@link TaskContract.Properties} table.
+ *
+ * @author Gabor Keszthelyi
+ */
+public final class SubtaskRelation implements InsertOperation<TaskContract.Properties>
+{
+
+    private final Operation<TaskContract.Properties> mDelegate;
+
+
+    public SubtaskRelation(String authority, RowSnapshot<TaskContract.Tasks> subtask, RowSnapshot<TaskContract.Tasks> parentTask)
+    {
+        mDelegate = new Insert<>(new PropertiesTable(authority), new ParentTaskRelationData(parentTask, subtask));
+    }
+
+
+    @NonNull
+    @Override
+    public Optional<SoftRowReference<TaskContract.Properties>> reference()
+    {
+        return mDelegate.reference();
+    }
+
+
+    @NonNull
+    @Override
+    public ContentProviderOperation.Builder contentOperationBuilder(@NonNull TransactionContext transactionContext) throws UnsupportedOperationException
+    {
+        return mDelegate.contentOperationBuilder(transactionContext);
+    }
+}
diff --git a/opentaskspal/src/main/java/org/dmfs/opentaskspal/predicates/IsProperty.java b/opentaskspal/src/main/java/org/dmfs/opentaskspal/predicates/IsProperty.java
new file mode 100644
index 000000000..9f93d3847
--- /dev/null
+++ b/opentaskspal/src/main/java/org/dmfs/opentaskspal/predicates/IsProperty.java
@@ -0,0 +1,36 @@
+/*
+ * Copyright 2017 dmfs GmbH
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.dmfs.opentaskspal.predicates;
+
+import org.dmfs.android.contentpal.Predicate;
+import org.dmfs.android.contentpal.predicates.DelegatingPredicate;
+import org.dmfs.android.contentpal.predicates.EqArg;
+import org.dmfs.tasks.contract.TaskContract;
+
+
+/**
+ * {@link Predicate} for selecting rows from {@link TaskContract.Properties} table representing a certain property identified by its mimeType.
+ *
+ * @author Gabor Keszthelyi
+ */
+public final class IsProperty extends DelegatingPredicate
+{
+    public IsProperty(String mimeType)
+    {
+        super(new EqArg(TaskContract.PropertyColumns.MIMETYPE, mimeType));
+    }
+}
diff --git a/opentaskspal/src/main/java/org/dmfs/opentaskspal/predicates/IsRelation.java b/opentaskspal/src/main/java/org/dmfs/opentaskspal/predicates/IsRelation.java
new file mode 100644
index 000000000..d130130c0
--- /dev/null
+++ b/opentaskspal/src/main/java/org/dmfs/opentaskspal/predicates/IsRelation.java
@@ -0,0 +1,35 @@
+/*
+ * Copyright 2017 dmfs GmbH
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.dmfs.opentaskspal.predicates;
+
+import org.dmfs.android.contentpal.Predicate;
+import org.dmfs.android.contentpal.predicates.DelegatingPredicate;
+import org.dmfs.tasks.contract.TaskContract;
+
+
+/**
+ * {@link Predicate} for selecting {@link TaskContract.Property.Relation} properties from {@link TaskContract.Properties} table.
+ *
+ * @author Gabor Keszthelyi
+ */
+public final class IsRelation extends DelegatingPredicate
+{
+    public IsRelation()
+    {
+        super(new IsProperty(TaskContract.Property.Relation.CONTENT_ITEM_TYPE));
+    }
+}
diff --git a/opentaskspal/src/main/java/org/dmfs/opentaskspal/rowsets/Subtasks.java b/opentaskspal/src/main/java/org/dmfs/opentaskspal/rowsets/Subtasks.java
new file mode 100644
index 000000000..1d57f321f
--- /dev/null
+++ b/opentaskspal/src/main/java/org/dmfs/opentaskspal/rowsets/Subtasks.java
@@ -0,0 +1,44 @@
+/*
+ * Copyright 2017 dmfs GmbH
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.dmfs.opentaskspal.rowsets;
+
+import android.content.ContentProviderClient;
+import android.support.annotation.NonNull;
+
+import org.dmfs.android.contentpal.RowSet;
+import org.dmfs.android.contentpal.RowSnapshot;
+import org.dmfs.android.contentpal.predicates.ReferringTo;
+import org.dmfs.android.contentpal.rowsets.DelegatingRowSet;
+import org.dmfs.android.contentpal.rowsets.QueryRowSet;
+import org.dmfs.opentaskspal.views.TasksView;
+import org.dmfs.tasks.contract.TaskContract;
+
+
+/**
+ * {@link RowSet} for the subtasks of a given task.
+ *
+ * @author Gabor Keszthelyi
+ */
+public final class Subtasks extends DelegatingRowSet<TaskContract.Tasks>
+{
+
+    public Subtasks(String authority, ContentProviderClient client, @NonNull RowSnapshot<TaskContract.Tasks> parentTask)
+    {
+        super(new QueryRowSet<>(new TasksView(authority, client), new ReferringTo<>(TaskContract.Tasks.PARENT_ID, parentTask)));
+    }
+
+}
diff --git a/opentaskspal/src/main/java/org/dmfs/opentaskspal/tables/PropertiesTable.java b/opentaskspal/src/main/java/org/dmfs/opentaskspal/tables/PropertiesTable.java
new file mode 100644
index 000000000..cb74ed020
--- /dev/null
+++ b/opentaskspal/src/main/java/org/dmfs/opentaskspal/tables/PropertiesTable.java
@@ -0,0 +1,36 @@
+/*
+ * Copyright 2017 dmfs GmbH
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.dmfs.opentaskspal.tables;
+
+import org.dmfs.android.contentpal.Table;
+import org.dmfs.android.contentpal.tables.BaseTable;
+import org.dmfs.android.contentpal.tables.DelegatingTable;
+import org.dmfs.tasks.contract.TaskContract;
+
+
+/**
+ * {@link Table} for {@link TaskContract.Properties}.
+ *
+ * @author Gabor Keszthelyi
+ */
+public final class PropertiesTable extends DelegatingTable<TaskContract.Properties>
+{
+    public PropertiesTable(String authority)
+    {
+        super(new BaseTable<TaskContract.Properties>(TaskContract.Properties.getContentUri(authority)));
+    }
+}
diff --git a/opentaskspal/src/main/java/org/dmfs/opentaskspal/tasks/ChildTaskRelationData.java b/opentaskspal/src/main/java/org/dmfs/opentaskspal/tasks/ChildTaskRelationData.java
new file mode 100644
index 000000000..3f82111bc
--- /dev/null
+++ b/opentaskspal/src/main/java/org/dmfs/opentaskspal/tasks/ChildTaskRelationData.java
@@ -0,0 +1,44 @@
+/*
+ * Copyright 2017 dmfs GmbH
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.dmfs.opentaskspal.tasks;
+
+import org.dmfs.android.contentpal.RowData;
+import org.dmfs.android.contentpal.RowSnapshot;
+import org.dmfs.android.contentpal.rowdata.DelegatingRowData;
+import org.dmfs.tasks.contract.TaskContract;
+import org.dmfs.tasks.contract.TaskContract.Property.Relation.RelType;
+
+
+/**
+ * {@link RowData} to add the {@link RelType#CHILD} relation between the 2 given tasks, to the {@link TaskContract.Properties} table.
+ *
+ * @author Gabor Keszthelyi
+ */
+public final class ChildTaskRelationData extends DelegatingRowData<TaskContract.Properties>
+{
+    public ChildTaskRelationData(RowSnapshot<TaskContract.Tasks> childTask, RowSnapshot<TaskContract.Tasks> parentTask)
+    {
+        super(new RelationData(parentTask, RelType.CHILD, childTask));
+    }
+
+
+    public ChildTaskRelationData(CharSequence childTaskUid, RowSnapshot<TaskContract.Tasks> parentTask)
+    {
+        super(new RelationData(parentTask, RelType.CHILD, childTaskUid));
+    }
+
+}
diff --git a/opentaskspal/src/main/java/org/dmfs/opentaskspal/tasks/ParentTaskRelationData.java b/opentaskspal/src/main/java/org/dmfs/opentaskspal/tasks/ParentTaskRelationData.java
new file mode 100644
index 000000000..b4e395058
--- /dev/null
+++ b/opentaskspal/src/main/java/org/dmfs/opentaskspal/tasks/ParentTaskRelationData.java
@@ -0,0 +1,43 @@
+/*
+ * Copyright 2017 dmfs GmbH
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.dmfs.opentaskspal.tasks;
+
+import org.dmfs.android.contentpal.RowData;
+import org.dmfs.android.contentpal.RowSnapshot;
+import org.dmfs.android.contentpal.rowdata.DelegatingRowData;
+import org.dmfs.tasks.contract.TaskContract;
+import org.dmfs.tasks.contract.TaskContract.Property.Relation.RelType;
+
+
+/**
+ * {@link RowData} to add the {@link RelType#PARENT} relation between the 2 given tasks, to the {@link TaskContract.Properties} table.
+ *
+ * @author Gabor Keszthelyi
+ */
+public final class ParentTaskRelationData extends DelegatingRowData<TaskContract.Properties>
+{
+    public ParentTaskRelationData(RowSnapshot<TaskContract.Tasks> parentTask, RowSnapshot<TaskContract.Tasks> childTask)
+    {
+        super(new RelationData(childTask, RelType.PARENT, parentTask));
+    }
+
+    public ParentTaskRelationData(CharSequence parentTaskUid, RowSnapshot<TaskContract.Tasks> childTask)
+    {
+        super(new RelationData(childTask, RelType.PARENT, parentTaskUid));
+    }
+
+}
diff --git a/opentaskspal/src/main/java/org/dmfs/opentaskspal/tasks/RelationData.java b/opentaskspal/src/main/java/org/dmfs/opentaskspal/tasks/RelationData.java
new file mode 100644
index 000000000..e595ff375
--- /dev/null
+++ b/opentaskspal/src/main/java/org/dmfs/opentaskspal/tasks/RelationData.java
@@ -0,0 +1,59 @@
+/*
+ * Copyright 2017 dmfs GmbH
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.dmfs.opentaskspal.tasks;
+
+import android.support.annotation.NonNull;
+
+import org.dmfs.android.contentpal.RowData;
+import org.dmfs.android.contentpal.RowSnapshot;
+import org.dmfs.android.contentpal.rowdata.CharSequenceRowData;
+import org.dmfs.android.contentpal.rowdata.Composite;
+import org.dmfs.android.contentpal.rowdata.DelegatingRowData;
+import org.dmfs.android.contentpal.rowdata.RawRowData;
+import org.dmfs.android.contentpal.rowdata.Referring;
+import org.dmfs.tasks.contract.TaskContract;
+import org.dmfs.tasks.contract.TaskContract.Property.Relation.RelType;
+
+
+/**
+ * {@link RowData} for adding a {@link TaskContract.Property.Relation} property.
+ *
+ * @author Gabor Keszthelyi
+ */
+public final class RelationData extends DelegatingRowData<TaskContract.Properties>
+{
+    public RelationData(@NonNull RowSnapshot<TaskContract.Tasks> relatingTask,
+                        @NonNull RelType relType,
+                        @NonNull RowSnapshot<TaskContract.Tasks> relatedTask)
+    {
+        super(new Composite<>(
+                new Referring<TaskContract.Properties>(TaskContract.Property.Relation.TASK_ID, relatingTask),
+                new RawRowData<TaskContract.Properties>(TaskContract.Property.Relation.RELATED_TYPE, relType.ordinal()),
+                new Referring<TaskContract.Properties>(TaskContract.Property.Relation.RELATED_ID, relatedTask)));
+    }
+
+
+    public RelationData(@NonNull RowSnapshot<TaskContract.Tasks> relatingTask,
+                        @NonNull RelType relType,
+                        @NonNull CharSequence relatedTaskUid)
+    {
+        super(new Composite<>(
+                new Referring<TaskContract.Properties>(TaskContract.Property.Relation.TASK_ID, relatingTask),
+                new RawRowData<TaskContract.Properties>(TaskContract.Property.Relation.RELATED_TYPE, relType.ordinal()),
+                new CharSequenceRowData<TaskContract.Properties>(TaskContract.Property.Relation.RELATED_UID, relatedTaskUid)));
+    }
+}
diff --git a/opentaskspal/src/main/java/org/dmfs/opentaskspal/views/TaskListScoped.java b/opentaskspal/src/main/java/org/dmfs/opentaskspal/views/TaskListScoped.java
index 8fd7aa464..2bbf7594b 100644
--- a/opentaskspal/src/main/java/org/dmfs/opentaskspal/views/TaskListScoped.java
+++ b/opentaskspal/src/main/java/org/dmfs/opentaskspal/views/TaskListScoped.java
@@ -64,4 +64,12 @@ public Table<TaskContract.Tasks> table()
     {
         return new org.dmfs.opentaskspal.tables.TaskListScoped(mTaskListRow, mDelegate.table());
     }
+
+
+    @NonNull
+    @Override
+    public View<TaskContract.Tasks> withProjection(@NonNull String... strings)
+    {
+        return mDelegate.withProjection(strings);
+    }
 }
diff --git a/opentaskspal/src/main/java/org/dmfs/opentaskspal/views/TasksView.java b/opentaskspal/src/main/java/org/dmfs/opentaskspal/views/TasksView.java
new file mode 100644
index 000000000..986cac3e9
--- /dev/null
+++ b/opentaskspal/src/main/java/org/dmfs/opentaskspal/views/TasksView.java
@@ -0,0 +1,38 @@
+/*
+ * Copyright 2017 dmfs GmbH
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.dmfs.opentaskspal.views;
+
+import android.content.ContentProviderClient;
+
+import org.dmfs.android.contentpal.View;
+import org.dmfs.android.contentpal.views.BaseView;
+import org.dmfs.android.contentpal.views.DelegatingView;
+import org.dmfs.tasks.contract.TaskContract;
+
+
+/**
+ * {@link View} for the {@link TaskContract.Tasks} table.
+ *
+ * @author Gabor Keszthelyi
+ */
+public final class TasksView extends DelegatingView<TaskContract.Tasks>
+{
+    public TasksView(String authority, ContentProviderClient client)
+    {
+        super(new BaseView<TaskContract.Tasks>(client, TaskContract.Tasks.getContentUri(authority)));
+    }
+}