diff --git a/app/models/relation.rb b/app/models/relation.rb
index f4586932e6..87c9426acb 100644
--- a/app/models/relation.rb
+++ b/app/models/relation.rb
@@ -33,22 +33,60 @@ class Relation < ActiveRecord::Base
 
   scope :of_work_package, ->(work_package) { where('from_id = ? OR to_id = ?', work_package, work_package) }
 
-  TYPE_RELATES      = 'relates'
-  TYPE_DUPLICATES   = 'duplicates'
-  TYPE_DUPLICATED   = 'duplicated'
-  TYPE_BLOCKS       = 'blocks'
-  TYPE_BLOCKED      = 'blocked'
-  TYPE_PRECEDES     = 'precedes'
-  TYPE_FOLLOWS      = 'follows'
-
-  TYPES = { TYPE_RELATES =>     { name: :label_relates_to, sym_name: :label_relates_to, order: 1, sym: TYPE_RELATES },
-            TYPE_DUPLICATES =>  { name: :label_duplicates, sym_name: :label_duplicated_by, order: 2, sym: TYPE_DUPLICATED },
-            TYPE_DUPLICATED =>  { name: :label_duplicated_by, sym_name: :label_duplicates, order: 3, sym: TYPE_DUPLICATES, reverse: TYPE_DUPLICATES },
-            TYPE_BLOCKS =>      { name: :label_blocks, sym_name: :label_blocked_by, order: 4, sym: TYPE_BLOCKED },
-            TYPE_BLOCKED =>     { name: :label_blocked_by, sym_name: :label_blocks, order: 5, sym: TYPE_BLOCKS, reverse: TYPE_BLOCKS },
-            TYPE_PRECEDES =>    { name: :label_precedes, sym_name: :label_follows, order: 6, sym: TYPE_FOLLOWS },
-            TYPE_FOLLOWS =>     { name: :label_follows, sym_name: :label_precedes, order: 7, sym: TYPE_PRECEDES, reverse: TYPE_PRECEDES }
-          }.freeze
+  TYPE_RELATES      = 'relates'.freeze
+  TYPE_DUPLICATES   = 'duplicates'.freeze
+  TYPE_DUPLICATED   = 'duplicated'.freeze
+  TYPE_BLOCKS       = 'blocks'.freeze
+  TYPE_BLOCKED      = 'blocked'.freeze
+  TYPE_PRECEDES     = 'precedes'.freeze
+  TYPE_FOLLOWS      = 'follows'.freeze
+  TYPE_INCLUDES     = 'includes'.freeze
+  TYPE_PARTOF       = 'partof'.freeze
+  TYPE_REQUIRES     = 'requires'.freeze
+  TYPE_REQUIRED     = 'required'.freeze
+
+  TYPES = {
+    TYPE_RELATES => {
+      name: :label_relates_to, sym_name: :label_relates_to, order: 1, sym: TYPE_RELATES
+    },
+    TYPE_DUPLICATES => {
+      name: :label_duplicates, sym_name: :label_duplicated_by, order: 2, sym: TYPE_DUPLICATED
+    },
+    TYPE_DUPLICATED => {
+      name: :label_duplicated_by, sym_name: :label_duplicates, order: 3,
+      sym: TYPE_DUPLICATES, reverse: TYPE_DUPLICATES
+    },
+    TYPE_BLOCKS => {
+      name: :label_blocks, sym_name: :label_blocked_by, order: 4, sym: TYPE_BLOCKED
+    },
+    TYPE_BLOCKED => {
+      name: :label_blocked_by, sym_name: :label_blocks, order: 5,
+      sym: TYPE_BLOCKS, reverse: TYPE_BLOCKS
+    },
+    TYPE_PRECEDES => {
+      name: :label_precedes, sym_name: :label_follows, order: 6, sym: TYPE_FOLLOWS
+    },
+    TYPE_FOLLOWS => {
+      name: :label_follows, sym_name: :label_precedes, order: 7,
+      sym: TYPE_PRECEDES, reverse: TYPE_PRECEDES
+    },
+    TYPE_INCLUDES => {
+      name: :label_includes, sym_name: :label_includes, order: 8,
+      sym: TYPE_INCLUDES, reverse: TYPE_PARTOF
+    },
+    TYPE_PARTOF => {
+      name: :label_part_of, sym_name: :label_part_of, order: 9,
+      sym: TYPE_PARTOF, reverse: TYPE_INCLUDES
+    },
+    TYPE_REQUIRES => {
+      name: :label_requires, sym_name: :label_requires, order: 10,
+      sym: TYPE_REQUIRES, reverse: TYPE_REQUIRED
+    },
+    TYPE_REQUIRED => {
+      name: :label_required, sym_name: :label_required, order: 11,
+      sym: TYPE_REQUIRED, reverse: TYPE_REQUIRES
+    }
+  }.freeze
 
   validates_presence_of :from, :to, :relation_type
   validates_inclusion_of :relation_type, in: TYPES.keys
@@ -84,7 +122,7 @@ class Relation < ActiveRecord::Base
   end
 
   def label_for(work_package)
-    TYPES[relation_type] ? TYPES[relation_type][(from_id == work_package.id) ? :name : :sym_name] : :unknow
+    TYPES[relation_type] ? TYPES[relation_type][(from_id == work_package.id) ? :name : :sym_name] : :unknown
   end
 
   def update_schedule