diff --git a/Gemfile b/Gemfile
index e1a769d1a2..3adcc443ca 100644
--- a/Gemfile
+++ b/Gemfile
@@ -186,7 +186,7 @@ gem 'pundit'
 # API gems
 gem 'grape', '~> 0.7.0'
 gem 'roar',   '~> 0.12.6'
-gem 'yaks'
+gem 'reform'
 
 # Use the commented pure ruby gems, if you have not the needed prerequisites on
 # board to compile the native ones.  Note, that their use is discouraged, since
diff --git a/Gemfile.lock b/Gemfile.lock
index e1b8adb509..54a01200ae 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -61,9 +61,6 @@ GEM
       multi_json (~> 1.0)
     acts_as_list (0.2.0)
       activerecord (>= 3.0)
-    adamantium (0.2.0)
-      ice_nine (~> 0.11.0)
-      memoizable (~> 0.4.0)
     addressable (2.3.4)
     arel (3.0.3)
     awesome_nested_set (2.1.6)
@@ -106,9 +103,6 @@ GEM
     coffee-script-source (1.6.2)
     color-tools (1.3.0)
     columnize (0.3.6)
-    concord (0.1.5)
-      adamantium (~> 0.2.0)
-      equalizer (~> 0.0.9)
     cucumber (1.3.8)
       builder (>= 2.1.2)
       diff-lcs (>= 1.1.3)
@@ -142,6 +136,9 @@ GEM
     descendants_tracker (0.0.4)
       thread_safe (~> 0.3, >= 0.3.1)
     diff-lcs (1.2.5)
+    disposable (0.0.3)
+      representable (~> 1.8.1)
+      uber
     equalizer (0.0.9)
     erubis (2.7.0)
     eventmachine (1.0.3)
@@ -187,13 +184,11 @@ GEM
     guard-test (1.0.0)
       guard (>= 1.8)
       test-unit (~> 2.2)
-    hamster (0.4.3)
     hashie (2.1.1)
     hike (1.2.3)
     htmldiff (0.0.1)
     i18n (0.6.5)
     ice_nine (0.11.0)
-    inflection (1.0.0)
     interception (0.3)
     journey (1.0.4)
     jquery-atwho-rails (0.4.7)
@@ -220,8 +215,6 @@ GEM
     mail (2.5.4)
       mime-types (~> 1.16)
       treetop (~> 1.4.8)
-    memoizable (0.4.2)
-      thread_safe (~> 0.3, >= 0.3.1)
     metaclass (0.0.1)
     method_source (0.8.2)
     mime-types (1.25.1)
@@ -309,6 +302,11 @@ GEM
     rdoc (3.12.2)
       json (~> 1.4)
     ref (1.0.5)
+    reform (1.0.0)
+      activemodel
+      disposable (~> 0.0.3)
+      representable (~> 1.8.1)
+      uber (~> 0.0.4)
     representable (1.8.1)
       multi_json
       nokogiri
@@ -398,7 +396,6 @@ GEM
     uglifier (2.1.1)
       execjs (>= 0.3.0)
       multi_json (~> 1.0, >= 1.0.2)
-    uri_template (0.6.0)
     virtus (1.0.2)
       axiom-types (~> 0.1)
       coercible (~> 1.0)
@@ -408,11 +405,6 @@ GEM
     will_paginate (3.0.5)
     xpath (2.0.0)
       nokogiri (~> 1.3)
-    yaks (0.2.0)
-      concord (~> 0.1.4)
-      hamster (~> 0.4.3)
-      inflection (~> 1.0.0)
-      uri_template (~> 0.6.0)
     yard (0.8.7.2)
 
 PLATFORMS
@@ -479,6 +471,7 @@ DEPENDENCIES
   rb-fsevent
   rb-readline
   rdoc (>= 2.4.2)
+  reform
   request_store
   roar (~> 0.12.6)
   rspec (~> 2.14)
@@ -503,4 +496,3 @@ DEPENDENCIES
   timecop (~> 0.6.1)
   uglifier (>= 1.0.3)
   will_paginate (~> 3.0)
-  yaks
diff --git a/app/api/api.rb b/app/api/api.rb
index ee2aff7e09..5223975274 100644
--- a/app/api/api.rb
+++ b/app/api/api.rb
@@ -52,5 +52,4 @@ class API < Grape::API
   mount Projects::API
   mount WorkPackages::API
   mount Users::API
-
 end
diff --git a/app/api/work_packages/relation_mapper.rb b/app/api/work_packages/relation_mapper.rb
deleted file mode 100644
index b911348baa..0000000000
--- a/app/api/work_packages/relation_mapper.rb
+++ /dev/null
@@ -1,11 +0,0 @@
-module WorkPackages
-  class RelationMapper < Yaks::Mapper
-    link :self, '/api/v3/work_packages/{work_package_id}/relations'
-
-    attributes :id
-
-    def work_package_id
-      1
-    end
-  end
-end
diff --git a/app/api/work_packages/user_representer.rb b/app/api/work_packages/user_representer.rb
new file mode 100644
index 0000000000..5addddebbc
--- /dev/null
+++ b/app/api/work_packages/user_representer.rb
@@ -0,0 +1,26 @@
+require 'roar/representer/json'
+require 'roar/decorator'
+require 'roar/representer/json/hal'
+
+module WorkPackages
+  class UserRepresenter < Roar::Decorator
+    include Roar::Representer::JSON
+    include Roar::Representer::JSON::HAL
+    include Roar::Representer::Feature::Hypermedia
+    include Rails.application.routes.url_helpers
+
+    property :login
+    property :firstname
+    property :lastname
+    property :mail
+    property :_type, exec_context: :decorator
+
+    link :self do
+      { href: "http://localhost:3000/api/v3/users/#{represented.id}", title: "User." }
+    end
+
+    def _type
+      "User"
+    end
+  end
+end
diff --git a/app/api/work_packages/work_package_mapper.rb b/app/api/work_packages/work_package_mapper.rb
deleted file mode 100644
index ed5f151c65..0000000000
--- a/app/api/work_packages/work_package_mapper.rb
+++ /dev/null
@@ -1,90 +0,0 @@
-module WorkPackages
-  class WorkPackageMapper < Yaks::Mapper
-    def initialize(object, embedded)
-        super(object)
-    end
-
-    link :self, '/api/v3/work_packages/{id}'
-    link :createChildren, '/api/v3/work_packages?parent_id={id}', method: :post
-    link :update, '/api/v3/work_packages/{id}', method: :patch
-    link :delete, '/api/v3/work_packages/{id}', method: :delete
-    link :project, '/api/v3/projects/{project_id}'
-    link :author, '/api/v3/users/{author_id}'
-    link :assignee, '/api/v3/users/{assigned_to_id}'
-    link :responsible, '/api/v3/users/{responsible_id}'
-    link :targetVersion, '/api/v3/versions/{fixed_version_id}'
-    link :projectWorkPackages, '/api/v3/work_packages?filter=project_ideql{project_id}'
-    link :descendants, '/api/v3/work_packages?filter=ancestors_idscontain{id}'
-    link :children, '/api/v3/work_packages?filter=parent_ideql{id}'
-    link :parent, '/api/v3/work_packages?filter=children_idscontain{id}'
-    link :ancestors, '/api/v3/work_packages?filter=descendants_idscontain{id}'
-    link :relations, '/api/v3/work_packages/{id}/relations'
-
-    attributes :id, :subject, :description, :type, :dueDate, :status, :priority, :percentageDone,
-        :estimatedTime, :startDate, :createdAt, :updatedAt, :customFields, :_type
-
-    has_one :project, mapper: Projects::ProjectMapper
-    has_one :author, mapper: Users::UserMapper
-    has_one :assigned_to, mapper: Users::UserMapper, as: :assignee
-    has_one :responsible, mapper: Users::UserMapper
-    has_one :fixed_version, mapper: Versions::VersionMapper, as: :targetVersion
-    has_one :parent, mapper: WorkPackages::WorkPackageMapper
-
-    has_many :descendants, mapper: WorkPackages::WorkPackageMapper
-    has_many :ancestors, mapper: WorkPackages::WorkPackageMapper
-    has_many :children, mapper: WorkPackages::WorkPackageMapper
-    has_many :relations, mapper: WorkPackages::RelationMapper
-
-    def type
-        object.type.name
-    end
-
-    def dueDate
-        object.due_date.to_s
-    end
-
-    def status
-        object.status.name
-    end
-
-    def priority
-        object.priority.name
-    end
-
-    def percentageDone
-        object.done_ratio
-    end
-
-    def estimatedTime
-        { unit: 'hours', value: object.estimated_hours }
-    end
-
-    def startDate
-        object.start_date.to_s
-    end
-
-    def createdAt
-      object.created_at.to_s
-    end
-
-    def updatedAt
-      object.updated_at.to_s
-    end
-
-    def customFields
-        fields = [ ]
-        object.custom_field_values.each do |custom_value|
-            fields << { name: custom_value.custom_field.name, format: custom_value.custom_field.field_format, value: custom_value.value }
-        end
-        fields
-    end
-
-    def _type
-        "WorkPackage"
-    end
-
-    def relations
-        []
-    end
-  end
-end
diff --git a/app/api/work_packages/work_package_model.rb b/app/api/work_packages/work_package_model.rb
new file mode 100644
index 0000000000..ffe217a966
--- /dev/null
+++ b/app/api/work_packages/work_package_model.rb
@@ -0,0 +1,80 @@
+module WorkPackages
+  class WorkPackageModel < Reform::Form
+    include Composition
+
+    model :work_package
+
+    property :subject, on: :work_package
+    property :description, on: :work_package
+    property :due_date, on: :work_package
+    property :percentage_done, as: :done_ratio, on: :work_package
+    property :start_date, on: :work_package
+    property :created_at, on: :work_package
+    property :updated_at, on: :work_package
+    property :author, on: :work_package
+
+    def type
+      work_package.type.name
+    end
+
+    def type=(value)
+      type = Type.find(:first, conditions: ['name ilike ?', value])
+      work_package.type = type
+    end
+
+    def status
+      work_package.status.name
+    end
+
+    def status=(value)
+      status = Status.find(:first, conditions: ['name ilike ?', value])
+      work_package.status = status
+    end
+
+    def priority
+      work_package.priority.name
+    end
+
+    def priority=(value)
+      priority = IssuePriority.find(:first, conditions: ['name ilike ?', value])
+      work_package.priority = priority
+    end
+
+    def  responsible_login
+      work_package.responsible.try(:login)
+    end
+
+    def responsible_login=(value)
+      responsible_user = User.find(:first, conditions: ['login ilike ?', value])
+      work_package.responsible = responsible_user
+    end
+
+    def responsible
+      work_package.responsible
+    end
+
+    def  assignee_login
+      work_package.assigned_to.try(:login)
+    end
+
+    def assignee_login=(value)
+      assignee_user = User.find(:first, conditions: ['login ilike ?', value])
+      work_package.assigned_to = assignee_user
+    end
+
+    def assignee
+      work_package.assigned_to
+    end
+
+    def estimated_time
+      { units: 'hours', value: work_package.estimated_hours }
+    end
+
+    def estimated_time=(value)
+      hours = ActiveSupport::JSON.decode(value)['value']
+      work_package.estimated_hours = hours
+    end
+
+    validates :subject, presence: true
+  end
+end
diff --git a/app/api/work_packages/work_package_representer.rb b/app/api/work_packages/work_package_representer.rb
index f702c2c766..b56f25be7f 100644
--- a/app/api/work_packages/work_package_representer.rb
+++ b/app/api/work_packages/work_package_representer.rb
@@ -2,48 +2,47 @@ require 'roar/representer/json'
 require 'roar/decorator'
 require 'roar/representer/json/hal'
 
-class WorkPackageRepresenter < Roar::Decorator
-  include Roar::Representer::JSON
-  include Roar::Representer::JSON::HAL
-  include Roar::Representer::Feature::Hypermedia
-  include Rails.application.routes.url_helpers
+module WorkPackages
+  class WorkPackageRepresenter < Roar::Decorator
+    include Roar::Representer::JSON
+    include Roar::Representer::JSON::HAL
+    include Roar::Representer::Feature::Hypermedia
+    include Rails.application.routes.url_helpers
 
-  property :id
-  property :subject
-  property :description
-  property :type, getter: lambda { |*| self.type.try(:name) }
-  property :due_date, as: :dueDate, getter: lambda { |*| self.due_date.try(:to_s) }
-  property :status, getter: lambda { |*| self.status.try(:name) }
-  property :priority, getter: lambda { |*| self.priority.try(:name) }
-  property :done_ratio, as: :percentageDone
-  property :estimated_time, as: :estimatedTime, exec_context: :decorator
-  property :start_date, as: :startDate, getter: lambda { |*| self.start_date.try(:to_s) }
-  property :created_at, as: :createdAt, getter: lambda { |*| self.created_at.try(:to_s) }
-  property :updated_at, as: :updatedAt, getter: lambda { |*| self.updated_at.try(:to_s) }
-  property :custom_fields, as: :customFields, exec_context: :decorator
-  property :_type, exec_context: :decorator
-  property :_links, exec_context: :decorator
+    property :_type, exec_context: :decorator
 
-  def estimated_time
-    { units: :hours, value: represented.estimated_hours}
-  end
-
-  def custom_fields
-    fields = []
-    represented.custom_field_values.each do |value|
-      fields << { name: value.custom_field.name, format: value.custom_field.field_format, value: value.value }
+    link :self do
+      { href: "http://localhost:3000/api/v3/work_packages/#{represented.work_package.id}", title: "Work package" }
     end
-    fields
-  end
 
-  def _type
-    "WorkPackage"
-  end
+    property :id, getter: lambda { |*| work_package.id }
+    property :subject
+    property :type
+    property :description
+    property :status
+    property :priority
+    property :start_date
+    property :due_date
+    property :estimated_time
+    property :percentage_done
+    property :project_id, getter: lambda { |*| work_package.project.id }
+    property :project_name, getter: lambda { |*| work_package.project.name }
+    property :responsible_id, getter: lambda { |*| work_package.responsible.try(:id) }, render_nil: true
+    property :responsible_name, getter: lambda { |*| work_package.responsible.try(:name) }, render_nil: true
+    property :responsible_login, getter: lambda { |*| work_package.responsible.try(:login) }, render_nil: true
+    property :responsible_mail, getter: lambda { |*| work_package.responsible.try(:mail) }, render_nil: true
+    property :assignee_id, getter: lambda { |*| work_package.assigned_to.try(:id) }, render_nil: true
+    property :assignee_name, getter: lambda { |*| work_package.assigned_to.try(:name) }, render_nil: true
+    property :assignee_login, getter: lambda { |*| work_package.assigned_to.try(:login) }, render_nil: true
+    property :assignee_mail, getter: lambda { |*| work_package.assigned_to.try(:mail) }, render_nil: true
+    property :author_name, getter: lambda { |*| work_package.author.name }
+    property :author_login, getter: lambda { |*| work_package.author.login }
+    property :author_mail, getter: lambda { |*| work_package.author.mail }
+    property :created_at
+    property :updated_at
 
-  def _links
-    {
-      self: { href: api_v3_work_package_path(represented.id) },
-      update: { href: api_v3_work_package_path(represented.id), method: :put }
-    }
+    def _type
+      "WorkPackage"
+    end
   end
 end
diff --git a/app/api/work_packages/work_packages.rb b/app/api/work_packages/work_packages.rb
index 98909374c4..1b8442e507 100644
--- a/app/api/work_packages/work_packages.rb
+++ b/app/api/work_packages/work_packages.rb
@@ -29,7 +29,9 @@ module WorkPackages
         end
 
         get do
-          'show a work package'
+          work_package_model = WorkPackageModel.new(work_package: @work_package)
+          work_package_representer = WorkPackageRepresenter.new(work_package_model)
+          work_package_representer.to_json
         end
 
         put do
@@ -37,7 +39,16 @@ module WorkPackages
         end
 
         patch do
-          @work_package
+          work_package_model = WorkPackageModel.new(work_package: @work_package)
+          work_package_representer = WorkPackageRepresenter.new(work_package_model)
+          work_package_representer.from_json(request.POST.to_json)
+
+          if work_package_representer.represented.valid?
+            work_package_representer.represented.save!
+            work_package_representer.to_json
+          else
+            work_package_representer.represented.errors.to_json
+          end
         end
 
         delete do