diff --git a/lib/barby/barcode/bookland.rb b/lib/barby/barcode/bookland.rb
index 04c5a98..edbec07 100644
--- a/lib/barby/barcode/bookland.rb
+++ b/lib/barby/barcode/bookland.rb
@@ -16,6 +16,7 @@ module Barby
   #
   # If a prefix is not given, a default of 978 is used.
   class Bookland < EAN13
+    attr_accessor :isbn
 
     # isbn should be an ISBN number string, with or without an EAN prefix and an ISBN checksum
     # non-number formatting like hyphens or spaces are ignored
@@ -61,12 +62,11 @@ def initialize(isbn)
 
 
       def isbn=(isbn)
-        if match = PATTERN.match(isbn.gsub(/\D/, ''))
-          @number = match[:number]
-          @prefix = match[:prefix]
-        else
-          raise ArgumentError, "Not a valid ISBN: #{isbn}"
-        end
+        raise ArgumentError, "Not a valid ISBN: #{isbn}" if valid?
+
+        match = PATTERN.match(isbn.gsub(/\D/, ''))
+        @number = match[:number]
+        @prefix = match[:prefix]
       end
 
       def isbn
@@ -135,9 +135,15 @@ def inspect
         "#<#{self.class}:0x#{'%014x' % object_id} #{formatted_isbn}>"
       end
 
+      def valid?
+        !!PATTERN.match(isbn.gsub(/\D/, ''))
+      end
 
     end#class ISBN
 
+    def valid?
+      !!ISBN::PATTERN.match(isbn.gsub(/\D/, ''))
+    end
 
   end#class Bookland
 
diff --git a/lib/barby/barcode/code_25_iata.rb b/lib/barby/barcode/code_25_iata.rb
index 6aa9e5e..f17d5f7 100644
--- a/lib/barby/barcode/code_25_iata.rb
+++ b/lib/barby/barcode/code_25_iata.rb
@@ -18,6 +18,10 @@ def stop_encoding
       encoding_for_bars_without_end_space(STOP_ENCODING)
     end
 
+    def valid?
+      !!data
+    end
+
   end
 
 end
diff --git a/lib/barby/barcode/data_matrix.rb b/lib/barby/barcode/data_matrix.rb
index f872a8c..97c5b1e 100644
--- a/lib/barby/barcode/data_matrix.rb
+++ b/lib/barby/barcode/data_matrix.rb
@@ -41,6 +41,9 @@ def to_s
     end
 
 
+    def valid?
+      !!data
+    end
   end
 
 end
diff --git a/lib/barby/barcode/gs1_128.rb b/lib/barby/barcode/gs1_128.rb
index 94cacbd..746209c 100644
--- a/lib/barby/barcode/gs1_128.rb
+++ b/lib/barby/barcode/gs1_128.rb
@@ -39,7 +39,6 @@ def to_s
       "(#{application_identifier}) #{partial_data}"
     end
 
-
   end
 
 
diff --git a/lib/barby/barcode/pdf_417.rb b/lib/barby/barcode/pdf_417.rb
index 20e245b..65cd933 100644
--- a/lib/barby/barcode/pdf_417.rb
+++ b/lib/barby/barcode/pdf_417.rb
@@ -5,6 +5,8 @@
 
 module Barby
   class Pdf417 < Barcode2D
+    attr_reader :data
+
     DEFAULT_OPTIONS = {
       :options       => 0,
       :y_height      => 3,
@@ -72,5 +74,9 @@ def encoding
       end
       enc
     end
+
+    def valid?
+      !!data
+    end
   end
 end
\ No newline at end of file
diff --git a/lib/barby/barcode/qr_code.rb b/lib/barby/barcode/qr_code.rb
index 83f9c98..5f0cf29 100644
--- a/lib/barby/barcode/qr_code.rb
+++ b/lib/barby/barcode/qr_code.rb
@@ -88,6 +88,10 @@ def to_s
     end
 
 
+    def valid?
+      !!data
+    end
+
   private
   
     #Generate an RQRCode object with the available values
diff --git a/test/code_25_iata_test.rb b/test/code_25_iata_test.rb
index 14715cb..f5e7fa8 100644
--- a/test/code_25_iata_test.rb
+++ b/test/code_25_iata_test.rb
@@ -16,4 +16,7 @@ class Code25IATATest < Barby::TestCase
     @code.stop_encoding.must_equal '11101'
   end
 
+  it "should be valid" do
+    @code.valid?.must_equal true
+  end
 end
diff --git a/test/data_matrix_test.rb b/test/data_matrix_test.rb
index 6e971b7..f34ac50 100644
--- a/test/data_matrix_test.rb
+++ b/test/data_matrix_test.rb
@@ -27,4 +27,7 @@ class DataMatrixTest < Barby::TestCase
     @code.encoding.wont_equal prev_encoding
   end
 
+  it "should be valid" do
+    @code.valid?.must_equal true
+  end
 end
diff --git a/test/pdf_417_test.rb b/test/pdf_417_test.rb
index 7221b39..7f70a21 100644
--- a/test/pdf_417_test.rb
+++ b/test/pdf_417_test.rb
@@ -40,6 +40,10 @@ class Pdf417Test < Barby::TestCase
       enc[0].length.must_equal 117
     end
     
+    it "should be valid" do
+      @code.valid?.must_equal true
+    end
+
   end
 
 end
diff --git a/test/qr_code_test.rb b/test/qr_code_test.rb
index fc20644..121237f 100644
--- a/test/qr_code_test.rb
+++ b/test/qr_code_test.rb
@@ -68,7 +68,10 @@ class QrCodeTest < Barby::TestCase
     QrCode.new('123456789012345678901234567890').to_s.must_equal '12345678901234567890'
   end
 
-  
+  it "should be valid" do
+    @code.valid?.must_equal true
+  end
+
   private
   
   def rqrcode(code)