diff --git a/bin/pdd b/bin/pdd
index 9415e5f..1bc090e 100755
--- a/bin/pdd
+++ b/bin/pdd
@@ -33,11 +33,39 @@ opts = Slop.parse(ARGV, strict: true, help: true) do
   banner "Usage (#{PDD::VERSION}): pdd [options]"
   on 'v', 'verbose', 'Enable verbose mode'
   on 'version', 'Show current version'
-  on 's', 'source', 'Source directory to parse', argument: :required
-  on 'f', 'file', 'File to save XML into', argument: :required
-  on 'e', 'exclude', 'Glob pattern to exclude', as: Array, argument: :required
-  on 't', 'format', 'Format to use (xml|html)', argument: :required
-  on 'r', 'rule', 'Format to use (xml|html)', argument: :required, as: Array
+  on(
+    's',
+    'source',
+    'Source directory to parse',
+    argument: :required
+  )
+  on(
+    'f',
+    'file',
+    'File to save XML into',
+    argument: :required
+  )
+  on(
+    'e',
+    'exclude',
+    'Glob pattern to exclude',
+    as: Array,
+    argument: :required
+  )
+  on(
+    't',
+    'format',
+    'Format to use (xml|html)',
+    argument: :required
+  )
+  on(
+    'r',
+    'rule',
+    'Format to use (xml|html)',
+    argument: :required,
+    as: Array,
+    limit: 1
+  )
 end
 
 fail '-f is mandatory when using -v' if opts.verbose? && !opts.file?
diff --git a/features/applies_rules.feature b/features/applies_rules.feature
index 0d06918..83cf8a0 100644
--- a/features/applies_rules.feature
+++ b/features/applies_rules.feature
@@ -29,3 +29,13 @@ Feature: Applies Post-Parsing Rules
     When I run bin/pdd with ""
     Then Exit code is not zero
     Then Stdout contains "there are 2 duplicate"
+
+  Scenario: Throwing exception on duplicates
+    Given I have a "Sample.java" file with content:
+    """
+    @todo #13/DEV:15min Some text first
+    @todo #13/TEST:15min The text second
+    """
+    When I run bin/pdd with "--rule=available-roles:DEV,IMP"
+    Then Exit code is not zero
+    Then Stdout contains "defines role TEST"
diff --git a/lib/pdd.rb b/lib/pdd.rb
index 55ab862..f550cf4 100644
--- a/lib/pdd.rb
+++ b/lib/pdd.rb
@@ -26,6 +26,7 @@
 require 'pdd/rule/estimates'
 require 'pdd/rule/text'
 require 'pdd/rule/duplicates'
+require 'pdd/rule/roles'
 require 'nokogiri'
 require 'logger'
 require 'time'
@@ -47,7 +48,8 @@ class SchemaError < Error
     'min-estimate' => PDD::Rule::Estimate::Min,
     'max-estimate' => PDD::Rule::Estimate::Max,
     'min-words' => PDD::Rule::Text::MinWords,
-    'max-duplicates' => PDD::Rule::MaxDuplicates
+    'max-duplicates' => PDD::Rule::MaxDuplicates,
+    'available-roles' => PDD::Rule::Roles::Available
   }
 
   # Get logger.
@@ -139,7 +141,7 @@ def rules(xml)
         name, value = r.split(':')
         rule = RULES[name]
         fail "rule '#{name}' doesn't exist" if rule.nil?
-        rule.new(doc, value.to_i).errors.each do |e|
+        rule.new(doc, value).errors.each do |e|
           PDD.log.error e
           total += 1
         end
diff --git a/lib/pdd/rule/duplicates.rb b/lib/pdd/rule/duplicates.rb
index 6de51c9..0eb6a07 100644
--- a/lib/pdd/rule/duplicates.rb
+++ b/lib/pdd/rule/duplicates.rb
@@ -29,7 +29,7 @@ class MaxDuplicates
       # +xml+:: XML with puzzles
       def initialize(xml, max)
         @xml = xml
-        @max = max
+        @max = max.to_i
       end
 
       def errors
diff --git a/lib/pdd/rule/estimates.rb b/lib/pdd/rule/estimates.rb
index dcb5058..dfa968f 100644
--- a/lib/pdd/rule/estimates.rb
+++ b/lib/pdd/rule/estimates.rb
@@ -30,7 +30,7 @@ class Min
         # +xml+:: XML with puzzles
         def initialize(xml, min)
           @xml = xml
-          @min = min
+          @min = min.to_i
         end
 
         def errors
@@ -48,7 +48,7 @@ class Max
         # +xml+:: XML with puzzles
         def initialize(xml, min)
           @xml = xml
-          @min = min
+          @min = min.to_i
         end
 
         def errors
diff --git a/lib/pdd/rule/roles.rb b/lib/pdd/rule/roles.rb
new file mode 100644
index 0000000..30d943b
--- /dev/null
+++ b/lib/pdd/rule/roles.rb
@@ -0,0 +1,53 @@
+# encoding: utf-8
+#
+# Copyright (c) 2014 TechnoPark Corp.
+# Copyright (c) 2014 Yegor Bugayenko
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the 'Software'), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in all
+# copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+
+module PDD
+  module Rule
+    module Roles
+      # Rule for available roles checking.
+      class Available
+        # Ctor.
+        # +xml+:: XML with puzzles
+        def initialize(xml, roles)
+          @xml = xml
+          @roles = roles.split(',')
+        end
+
+        def errors
+          @xml.xpath('//puzzle').map do |p|
+            role = p.xpath('role/text()').to_s
+            next nil if @roles.include?(role)
+            "puzzle #{p.xpath('file/text()')}:#{p.xpath('lines/text()')}" +
+            if role.empty?
+              " doesn't define any role"\
+              ", while one of these roles is required: #{@roles}"
+            else
+              " defines role #{role}"\
+              ", while only these roles are allowed: #{@roles}"
+            end
+          end.compact
+        end
+      end
+    end
+  end
+end
diff --git a/lib/pdd/rule/text.rb b/lib/pdd/rule/text.rb
index b3c9399..601cf3b 100644
--- a/lib/pdd/rule/text.rb
+++ b/lib/pdd/rule/text.rb
@@ -30,7 +30,7 @@ class MinWords
         # +xml+:: XML with puzzles
         def initialize(xml, min)
           @xml = xml
-          @min = min
+          @min = min.to_i
         end
 
         def errors
diff --git a/test/test_roles.rb b/test/test_roles.rb
new file mode 100644
index 0000000..3d0e1ab
--- /dev/null
+++ b/test/test_roles.rb
@@ -0,0 +1,59 @@
+# encoding: utf-8
+#
+# Copyright (c) 2014 TechnoPark Corp.
+# Copyright (c) 2014 Yegor Bugayenko
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the 'Software'), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in all
+# copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+
+require 'minitest/autorun'
+require 'nokogiri'
+require 'pdd/rule/roles'
+
+# PDD::Rule::Role module tests.
+# Author:: Yegor Bugayenko (yegor@teamed.io)
+# Copyright:: Copyright (c) 2014 Yegor Bugayenko
+# License:: MIT
+class TestRoles < Minitest::Test
+  def test_incorrect_role
+    rule = PDD::Rule::Roles::Available.new(
+      Nokogiri::XML::Document.parse(
+        '<puzzles><puzzle><role>D</role></puzzle></puzzles>'
+      ), 'A,B,C'
+    )
+    assert !rule.errors.empty?, 'why it is empty?'
+  end
+
+  def test_correct_role
+    rule = PDD::Rule::Roles::Available.new(
+      Nokogiri::XML::Document.parse(
+        '<puzzles><puzzle><role>F</role></puzzle></puzzles>'
+      ), 'F,E,G'
+    )
+    assert rule.errors.empty?, 'why it is not empty?'
+  end
+
+  def test_empty_role
+    rule = PDD::Rule::Roles::Available.new(
+      Nokogiri::XML::Document.parse(
+        '<puzzles><puzzle></puzzle></puzzles>'
+      ), 'T,R,L'
+    )
+    assert !rule.errors.empty?, 'why it is empty?'
+  end
+end