diff --git a/lib/puppet/pops/types/type_factory.rb b/lib/puppet/pops/types/type_factory.rb
index 475366581..b170ee9b8 100644
--- a/lib/puppet/pops/types/type_factory.rb
+++ b/lib/puppet/pops/types/type_factory.rb
@@ -1,339 +1,416 @@
 # Helper module that makes creation of type objects simpler.
 # @api public
 #
 module Puppet::Pops::Types::TypeFactory
   @type_calculator = Puppet::Pops::Types::TypeCalculator.new()
 
   Types = Puppet::Pops::Types
 
   # Produces the Integer type
   # @api public
   #
   def self.integer()
     Types::PIntegerType.new()
   end
 
   # Produces an Integer range type
   # @api public
   #
   def self.range(from, to)
     t = Types::PIntegerType.new()
     t.from = from unless (from == :default || from == 'default')
     t.to = to unless (to == :default || to == 'default')
     t
   end
 
   # Produces a Float range type
   # @api public
   #
   def self.float_range(from, to)
     t = Types::PFloatType.new()
     t.from = Float(from) unless from == :default || from.nil?
     t.to = Float(to) unless to == :default || to.nil?
     t
   end
 
   # Produces the Float type
   # @api public
   #
   def self.float()
     Types::PFloatType.new()
   end
 
   # Produces the Numeric type
   # @api public
   #
   def self.numeric()
     Types::PNumericType.new()
   end
 
   # Produces a string representation of the type
   # @api public
   #
   def self.label(t)
     @type_calculator.string(t)
   end
 
   # Produces the String type, optionally with specific string values
   # @api public
   #
   def self.string(*values)
     t = Types::PStringType.new()
     values.each {|v| t.addValues(v) }
     t
   end
 
   # Produces the Optional type, i.e. a short hand for Variant[T, Undef]
   def self.optional(optional_type = nil)
     t = Types::POptionalType.new
     t.optional_type = type_of(optional_type)
     t
   end
 
+  # Convenience method to produce an Optional[Object] type
+  def self.optional_object()
+    optional(object())
+  end
+
   # Produces the Enum type, optionally with specific string values
   # @api public
   #
   def self.enum(*values)
     t = Types::PEnumType.new()
     values.each {|v| t.addValues(v) }
     t
   end
 
   # Produces the Variant type, optionally with the "one of" types
   # @api public
   #
   def self.variant(*types)
     t = Types::PVariantType.new()
     types.each {|v| t.addTypes(type_of(v)) }
     t
   end
 
   # Produces the Struct type, either a non parameterized instance representing all structs (i.e. all hashes)
   # or a hash with a given set of keys of String type (names), bound to a value of a given type. Type may be
   # a Ruby Class, a Puppet Type, or an instance from which the type is inferred.
   #
   def self.struct(name_type_hash = {})
     t = Types::PStructType.new
     name_type_hash.map do |name, type|
       elem = Types::PStructElement.new
       if name.is_a?(String) && name.empty?
         raise ArgumentError, "An empty String can not be used where a String[1, default] is expected"
       end
       elem.name = name
       elem.type = type_of(type)
       elem
     end.each {|elem| t.addElements(elem) }
     t
   end
 
   def self.tuple(*types)
     t = Types::PTupleType.new
     types.each {|elem| t.addTypes(type_of(elem)) }
     t
   end
 
   # Produces the Boolean type
   # @api public
   #
   def self.boolean()
     Types::PBooleanType.new()
   end
 
   # Produces the Object type
   # @api public
   #
   def self.object()
     Types::PObjectType.new()
   end
 
   # Produces the Regexp type
   # @param pattern [Regexp, String, nil] (nil) The regular expression object or a regexp source string, or nil for bare type
   # @api public
   #
   def self.regexp(pattern = nil)
     t = Types::PRegexpType.new()
     if pattern
       t.pattern = pattern.is_a?(Regexp) ? pattern.inspect[1..-2] : pattern
     end
     t.regexp() unless pattern.nil? # compile pattern to catch errors
     t
   end
 
   def self.pattern(*regular_expressions)
     t = Types::PPatternType.new()
     regular_expressions.each do |re|
       case re
       when String
         re_T = Types::PRegexpType.new()
         re_T.pattern = re
         re_T.regexp()  # compile it to catch errors
         t.addPatterns(re_T)
 
       when Regexp
         re_T = Types::PRegexpType.new()
         # Regep.to_s includes options user did not enter and does not escape source
         # to work either as a string or as a // regexp. The inspect method does a better
         # job, but includes the //
         re_T.pattern = re.inspect[1..-2]
         t.addPatterns(re_T)
 
       when Types::PRegexpType
         t.addPatterns(re.copy)
 
       when Types::PPatternType
         re.patterns.each do |p|
           t.addPatterns(p.copy)
         end
 
      else
        raise ArgumentError, "Only String, Regexp, Pattern-Type, and Regexp-Type are allowed: got '#{re.class}"
       end
     end
     t
   end
 
   # Produces the Literal type
   # @api public
   #
   def self.scalar()
     Types::PScalarType.new()
   end
 
+  # Produces a CallableType matching all callables
+  # @api public
+  #
+  def self.all_callables()
+    return Puppet::Pops::Types::PCallableType.new
+  end
+
+  # Produces a Callable type with one signature without support for a block
+  # Use #with_block, or #with_optional_block to add a block to the callable
+  # If no parameters are given, the Callable will describe a signature
+  # that does not accept parameters. To create a Callable that matches all callables
+  # use {#all_callables}.
+  #
+  # The params is a list of types, where the two last types may be a min, max count.
+  # If neither min or max are specified the parameters must match exactly.
+  # A min < params.size means that the difference are optional.
+  # If max > params.size means that the last type repeats.
+  # if max is :default, the max value is unbound (infinity).
+  # 
+  # Params are either given as a sequence of arguments to {#type_of}.
+  # Or as a sequence of arrays where each array is [type, name] which also names the parameters.
+  # If parameter names are not given, they are automatically generated as arg0 - argn.
+  # A mix of [type, name], and type is allowed, automatic naming then applies to
+  # unnamed entries.
+  #
+  def self.callable(*params)
+    callable = Types::PCallableType.new()
+    # compute a size_type for the signature based on the two last parameters
+    if is_range_parameter?(params[-2]) && is_range_parameter?(params[-1])
+      size_type = range(params[-2], params[-1])
+      params = params[0, params.size - 2]
+    elsif is_range_parameter?(params[-1])
+      size_type = range(params[-1], :default)
+      params = params[0, params.size - 1]
+    end
+
+    types = [ ]
+    names = [ ]
+    params.each_with_index do |p, index|
+      if p.is_a?(Array)
+        # type, name pair
+        t, n = p
+        unless (t && n) && n.is_a?(String)
+          raise ArgumentError, "Callable Type Expected [Type, String] entry, got '[#{t.class}, #{n.class}]'"
+        end
+        types << type_of(t)
+        names << n
+      else
+        types << type_of(p)
+        names << "arg#{index}"
+      end
+    end
+
+    # create a signature
+    callable_t = Types::PCallableType.new()
+    tuple_t = tuple(*types)
+    tuple_t.size_type = size_type unless size_type.nil?
+    callable_t.param_types = tuple_t
+    callable_t.param_names = names unless names.empty?
+    callable_t
+  end
+
+  def self.with_block(callable, *block_params)
+    callable.block_type = callable(*block_params)
+    callable
+  end
+
+  def self.with_optional_block(callable, *block_params)
+    callable.block_type = optional(callable(*block_params))
+    callable
+  end
+
   # Produces the abstract type Collection
   # @api public
   #
   def self.collection()
     Types::PCollectionType.new()
   end
 
   # Produces the Data type
   # @api public
   #
   def self.data()
     Types::PDataType.new()
   end
 
   # Creates an instance of the Undef type
   # @api public
   def self.undef()
     Types::PNilType.new()
   end
 
   # Produces an instance of the abstract type PCatalogEntryType
   def self.catalog_entry()
     Types::PCatalogEntryType.new()
   end
 
   # Produces a PResourceType with a String type_name
   # A PResourceType with a nil or empty name is compatible with any other PResourceType.
   # A PResourceType with a given name is only compatible with a PResourceType with the same name.
   # (There is no resource-type subtyping in Puppet (yet)).
   #
   def self.resource(type_name = nil, title = nil)
     type = Types::PResourceType.new()
     type_name = type_name.type_name if type_name.is_a?(Types::PResourceType)
     type.type_name = type_name.downcase unless type_name.nil?
     type.title = title
     type
   end
 
   # Produces PHostClassType with a string class_name.
   # A PHostClassType with nil or empty name is compatible with any other PHostClassType.
   # A PHostClassType with a given name is only compatible with a PHostClassType with the same name.
   #
   def self.host_class(class_name = nil)
     type = Types::PHostClassType.new()
     unless class_name.nil?
       type.class_name = class_name.sub(/^::/, '')
     end
     type
   end
 
   # Produces a type for Array[o] where o is either a type, or an instance for which a type is inferred.
   # @api public
   #
   def self.array_of(o)
     type = Types::PArrayType.new()
     type.element_type = type_of(o)
     type
   end
 
   # Produces a type for Hash[Scalar, o] where o is either a type, or an instance for which a type is inferred.
   # @api public
   #
   def self.hash_of(value, key = scalar())
     type = Types::PHashType.new()
     type.key_type = type_of(key)
     type.element_type = type_of(value)
     type
   end
 
   # Produces a type for Array[Data]
   # @api public
   #
   def self.array_of_data()
     type = Types::PArrayType.new()
     type.element_type = data()
     type
   end
 
   # Produces a type for Hash[Scalar, Data]
   # @api public
   #
   def self.hash_of_data()
     type = Types::PHashType.new()
     type.key_type = scalar()
     type.element_type = data()
     type
   end
 
   # Produces a type for Type[T]
   # @api public
   #
   def self.type_type(inst_type = nil)
     type = Types::PType.new()
     type.type = inst_type
     type
   end
 
   # Produce a type corresponding to the class of given unless given is a String, Class or a PAbstractType.
   # When a String is given this is taken as a classname.
   #
   def self.type_of(o)
     if o.is_a?(Class)
       @type_calculator.type(o)
     elsif o.is_a?(Types::PAbstractType)
       o
     elsif o.is_a?(String)
       type = Types::PRubyType.new()
       type.ruby_class = o
       type
     else
       @type_calculator.infer_generic(o)
     end
   end
 
   # Produces a type for a class or infers a type for something that is not a class
   # @note
   #   To get the type for the class' class use `TypeCalculator.infer(c)`
   #
   # @overload ruby(o)
   #   @param o [Class] produces the type corresponding to the class (e.g. Integer becomes PIntegerType)
   # @overload ruby(o)
   #   @param o [Object] produces the type corresponding to the instance class (e.g. 3 becomes PIntegerType)
   #
   # @api public
   #
   def self.ruby(o)
     if o.is_a?(Class)
       @type_calculator.type(o)
     else
       type = Types::PRubyType.new()
       type.ruby_class = o.class.name
       type
     end
   end
 
   # Generic creator of a RubyType - allows creating the Ruby type with nil name, or String name.
   # Also see ruby(o) which performs inference, or mapps a Ruby Class to its name.
   #
   def self.ruby_type(class_name = nil)
     type = Types::PRubyType.new()
     type.ruby_class = class_name
     type
   end
 
   # Sets the accepted size range of a collection if something other than the default 0 to Infinity
   # is wanted. The semantics for from/to are the same as for #range
   #
   def self.constrain_size(collection_t, from, to)
     collection_t.size_type = range(from, to)
     collection_t
   end
 
   # Returns true if the given type t is of valid range parameter type (integer or literal default).
   def self.is_range_parameter?(t)
     t.is_a?(Integer) || t == 'default' || t == :default
   end
 
 end
diff --git a/spec/unit/pops/types/type_factory_spec.rb b/spec/unit/pops/types/type_factory_spec.rb
index f533e6480..01d807ff0 100644
--- a/spec/unit/pops/types/type_factory_spec.rb
+++ b/spec/unit/pops/types/type_factory_spec.rb
@@ -1,175 +1,279 @@
 require 'spec_helper'
 require 'puppet/pops'
 
 describe 'The type factory' do
   context 'when creating' do
     it 'integer() returns PIntegerType' do
       Puppet::Pops::Types::TypeFactory.integer().class().should == Puppet::Pops::Types::PIntegerType
     end
 
     it 'float() returns PFloatType' do
       Puppet::Pops::Types::TypeFactory.float().class().should == Puppet::Pops::Types::PFloatType
     end
 
     it 'string() returns PStringType' do
       Puppet::Pops::Types::TypeFactory.string().class().should == Puppet::Pops::Types::PStringType
     end
 
     it 'boolean() returns PBooleanType' do
       Puppet::Pops::Types::TypeFactory.boolean().class().should == Puppet::Pops::Types::PBooleanType
     end
 
     it 'pattern() returns PPatternType' do
       Puppet::Pops::Types::TypeFactory.pattern().class().should == Puppet::Pops::Types::PPatternType
     end
 
     it 'regexp() returns PRegexpType' do
       Puppet::Pops::Types::TypeFactory.regexp().class().should == Puppet::Pops::Types::PRegexpType
     end
 
     it 'enum() returns PEnumType' do
       Puppet::Pops::Types::TypeFactory.enum().class().should == Puppet::Pops::Types::PEnumType
     end
 
     it 'variant() returns PVariantType' do
       Puppet::Pops::Types::TypeFactory.variant().class().should == Puppet::Pops::Types::PVariantType
     end
 
     it 'scalar() returns PScalarType' do
       Puppet::Pops::Types::TypeFactory.scalar().class().should == Puppet::Pops::Types::PScalarType
     end
 
     it 'data() returns PDataType' do
       Puppet::Pops::Types::TypeFactory.data().class().should == Puppet::Pops::Types::PDataType
     end
 
     it 'optional() returns POptionalType' do
       Puppet::Pops::Types::TypeFactory.optional().class().should == Puppet::Pops::Types::POptionalType
     end
 
     it 'collection() returns PCollectionType' do
       Puppet::Pops::Types::TypeFactory.collection().class().should == Puppet::Pops::Types::PCollectionType
     end
 
     it 'catalog_entry() returns PCatalogEntryType' do
       Puppet::Pops::Types::TypeFactory.catalog_entry().class().should == Puppet::Pops::Types::PCatalogEntryType
     end
 
     it 'struct() returns PStructType' do
       Puppet::Pops::Types::TypeFactory.struct().class().should == Puppet::Pops::Types::PStructType
     end
 
     it 'tuple() returns PTupleType' do
       Puppet::Pops::Types::TypeFactory.tuple().class().should == Puppet::Pops::Types::PTupleType
     end
 
     it 'undef() returns PNilType' do
       Puppet::Pops::Types::TypeFactory.undef().class().should == Puppet::Pops::Types::PNilType
     end
 
     it 'range(to, from) returns PIntegerType' do
       t = Puppet::Pops::Types::TypeFactory.range(1,2)
       t.class().should == Puppet::Pops::Types::PIntegerType
       t.from.should == 1
       t.to.should == 2
     end
 
     it 'range(default, default) returns PIntegerType' do
       t = Puppet::Pops::Types::TypeFactory.range(:default,:default)
       t.class().should == Puppet::Pops::Types::PIntegerType
       t.from.should == nil
       t.to.should == nil
     end
 
     it 'float_range(to, from) returns PFloatType' do
       t = Puppet::Pops::Types::TypeFactory.float_range(1.0, 2.0)
       t.class().should == Puppet::Pops::Types::PFloatType
       t.from.should == 1.0
       t.to.should == 2.0
     end
 
     it 'float_range(default, default) returns PFloatType' do
       t = Puppet::Pops::Types::TypeFactory.float_range(:default, :default)
       t.class().should == Puppet::Pops::Types::PFloatType
       t.from.should == nil
       t.to.should == nil
     end
 
     it 'resource() creates a generic PResourceType' do
       pr = Puppet::Pops::Types::TypeFactory.resource()
       pr.class().should == Puppet::Pops::Types::PResourceType
       pr.type_name.should == nil
     end
 
     it 'resource(x) creates a PResourceType[x]' do
       pr = Puppet::Pops::Types::TypeFactory.resource('x')
       pr.class().should == Puppet::Pops::Types::PResourceType
       pr.type_name.should == 'x'
     end
 
     it 'host_class() creates a generic PHostClassType' do
       hc = Puppet::Pops::Types::TypeFactory.host_class()
       hc.class().should == Puppet::Pops::Types::PHostClassType
       hc.class_name.should == nil
     end
 
     it 'host_class(x) creates a PHostClassType[x]' do
       hc = Puppet::Pops::Types::TypeFactory.host_class('x')
       hc.class().should == Puppet::Pops::Types::PHostClassType
       hc.class_name.should == 'x'
     end
 
     it 'host_class(::x) creates a PHostClassType[x]' do
       hc = Puppet::Pops::Types::TypeFactory.host_class('::x')
       hc.class().should == Puppet::Pops::Types::PHostClassType
       hc.class_name.should == 'x'
     end
 
     it 'array_of(fixnum) returns PArrayType[PIntegerType]' do
       at = Puppet::Pops::Types::TypeFactory.array_of(1)
       at.class().should == Puppet::Pops::Types::PArrayType
       at.element_type.class.should == Puppet::Pops::Types::PIntegerType
     end
 
     it 'array_of(PIntegerType) returns PArrayType[PIntegerType]' do
       at = Puppet::Pops::Types::TypeFactory.array_of(Puppet::Pops::Types::PIntegerType.new())
       at.class().should == Puppet::Pops::Types::PArrayType
       at.element_type.class.should == Puppet::Pops::Types::PIntegerType
     end
 
     it 'array_of_data returns PArrayType[PDataType]' do
       at = Puppet::Pops::Types::TypeFactory.array_of_data
       at.class().should == Puppet::Pops::Types::PArrayType
       at.element_type.class.should == Puppet::Pops::Types::PDataType
     end
 
     it 'hash_of_data returns PHashType[PScalarType,PDataType]' do
       ht = Puppet::Pops::Types::TypeFactory.hash_of_data
       ht.class().should == Puppet::Pops::Types::PHashType
       ht.key_type.class.should == Puppet::Pops::Types::PScalarType
       ht.element_type.class.should == Puppet::Pops::Types::PDataType
     end
 
     it 'ruby(1) returns PRubyType[\'Fixnum\']' do
       ht = Puppet::Pops::Types::TypeFactory.ruby(1)
       ht.class().should == Puppet::Pops::Types::PRubyType
       ht.ruby_class.should == 'Fixnum'
     end
 
     it 'a size constrained collection can be created from array' do
       t = Puppet::Pops::Types::TypeFactory.array_of_data()
       Puppet::Pops::Types::TypeFactory.constrain_size(t, 1,2).should == t
       t.size_type.class.should == Puppet::Pops::Types::PIntegerType
       t.size_type.from.should == 1
       t.size_type.to.should == 2
     end
 
     it 'a size constrained collection can be created from hash' do
       t = Puppet::Pops::Types::TypeFactory.hash_of_data()
       Puppet::Pops::Types::TypeFactory.constrain_size(t, 1,2).should == t
       t.size_type.class.should == Puppet::Pops::Types::PIntegerType
       t.size_type.from.should == 1
       t.size_type.to.should == 2
     end
+
+    context 'callable types' do
+      it 'the callable methods produces a Callable' do
+        t = Puppet::Pops::Types::TypeFactory.callable()
+        expect(t.class).to be(Puppet::Pops::Types::PCallableType)
+        expect(t.param_types.class).to be(Puppet::Pops::Types::PTupleType)
+        expect(t.param_types.types).to be_empty
+        expect(t.param_names).to be_empty
+        expect(t.block_type).to be_nil
+      end
+
+      it 'callable method with types produces the corresponding Tuple for parameters and generated names' do
+        tf = Puppet::Pops::Types::TypeFactory
+        t = tf.callable(tf.integer, tf.string)
+        expect(t.class).to be(Puppet::Pops::Types::PCallableType)
+        expect(t.param_types.class).to be(Puppet::Pops::Types::PTupleType)
+        expect(t.param_types.types).to eql([tf.integer, tf.string])
+        expect(t.param_names).to eql(['arg0', 'arg1'])
+        expect(t.block_type).to be_nil
+      end
+
+      it 'callable method with types produces the corresponding Tuple for parameters with given names' do
+        tf = Puppet::Pops::Types::TypeFactory
+        t = tf.callable([tf.integer, 'a'], [tf.string, 'b'])
+        expect(t.class).to be(Puppet::Pops::Types::PCallableType)
+        expect(t.param_types.class).to be(Puppet::Pops::Types::PTupleType)
+        expect(t.param_types.types).to eql([tf.integer, tf.string])
+        expect(t.param_names).to eql(['a', 'b'])
+        expect(t.block_type).to be_nil
+      end
+
+      it 'callable assigns names for params without name' do
+        tf = Puppet::Pops::Types::TypeFactory
+        t = tf.callable([tf.integer, 'a'], tf.string)
+        expect(t.class).to be(Puppet::Pops::Types::PCallableType)
+        expect(t.param_types.class).to be(Puppet::Pops::Types::PTupleType)
+        expect(t.param_types.types).to eql([tf.integer, tf.string])
+        expect(t.param_names).to eql(['a', 'arg1'])
+        expect(t.block_type).to be_nil
+      end
+
+      it 'callable accepts min range to be given' do
+        tf = Puppet::Pops::Types::TypeFactory
+        t = tf.callable([tf.integer, 'a'], tf.string, 1)
+        expect(t.class).to be(Puppet::Pops::Types::PCallableType)
+        expect(t.param_types.class).to be(Puppet::Pops::Types::PTupleType)
+        expect(t.param_types.size_type.from).to eql(1)
+        expect(t.param_types.size_type.to).to be_nil
+      end
+
+      it 'callable accepts max range to be given' do
+        tf = Puppet::Pops::Types::TypeFactory
+        t = tf.callable([tf.integer, 'a'], tf.string, 1, 3)
+        expect(t.class).to be(Puppet::Pops::Types::PCallableType)
+        expect(t.param_types.class).to be(Puppet::Pops::Types::PTupleType)
+        expect(t.param_types.size_type.from).to eql(1)
+        expect(t.param_types.size_type.to).to eql(3)
+      end
+
+      it 'callable accepts max range to be given as :default' do
+        tf = Puppet::Pops::Types::TypeFactory
+        t = tf.callable([tf.integer, 'a'], tf.string, 1, :default)
+        expect(t.class).to be(Puppet::Pops::Types::PCallableType)
+        expect(t.param_types.class).to be(Puppet::Pops::Types::PTupleType)
+        expect(t.param_types.size_type.from).to eql(1)
+        expect(t.param_types.size_type.to).to be_nil
+      end
+
+      it 'the all_callables method produces a Callable matching any Callable' do
+        t = Puppet::Pops::Types::TypeFactory.all_callables()
+        expect(t.class).to be(Puppet::Pops::Types::PCallableType)
+        expect(t.param_types).to be_nil
+        expect(t.param_names).to be_empty
+        expect(t.block_type).to be_nil
+      end
+
+      it 'the with_block methods decorates a Callable with a block_type' do
+        t = Puppet::Pops::Types::TypeFactory.callable()
+        t2 = Puppet::Pops::Types::TypeFactory.with_block(t)
+        block_t = t2.block_type
+        # given t is returned after mutation
+        expect(t2).to be(t)
+        expect(block_t.class).to be(Puppet::Pops::Types::PCallableType)
+        expect(block_t.param_types.class).to be(Puppet::Pops::Types::PTupleType)
+        expect(block_t.param_types.types).to be_empty
+        expect(block_t.param_names).to be_empty
+        expect(block_t.block_type).to be_nil
+      end
+
+      it 'the with_optional_block methods decorates a Callable with an optional block_type' do
+        t = Puppet::Pops::Types::TypeFactory.callable()
+        t2 = Puppet::Pops::Types::TypeFactory.with_optional_block(t)
+        opt_t = t2.block_type
+        expect(opt_t.class).to be(Puppet::Pops::Types::POptionalType)
+        block_t = opt_t.optional_type
+        # given t is returned after mutation
+        expect(t2).to be(t)
+        expect(block_t.class).to be(Puppet::Pops::Types::PCallableType)
+        expect(block_t.param_types.class).to be(Puppet::Pops::Types::PTupleType)
+        expect(block_t.param_types.types).to be_empty
+        expect(block_t.param_names).to be_empty
+        expect(block_t.block_type).to be_nil
+      end
+    end
   end
 end