diff --git a/lib/rexml/parsers/baseparser.rb b/lib/rexml/parsers/baseparser.rb
index ca29b4a9..935cbd9e 100644
--- a/lib/rexml/parsers/baseparser.rb
+++ b/lib/rexml/parsers/baseparser.rb
@@ -50,7 +50,6 @@ class BaseParser
 
       DOCTYPE_START = /\A\s*<!DOCTYPE\s/um
       DOCTYPE_END = /\A\s*\]\s*>/um
-      DOCTYPE_PATTERN = /\s*<!DOCTYPE\s+(.*?)(\[|>)/um
       ATTRIBUTE_PATTERN = /\s*(#{QNAME_STR})\s*=\s*(["'])(.*?)\4/um
       COMMENT_START = /\A<!--/u
       COMMENT_PATTERN = /<!--(.*?)-->/um
@@ -69,7 +68,6 @@ class BaseParser
       STANDALONE = /\bstandalone\s*=\s*["'](.*?)['"]/um
 
       ENTITY_START = /\A\s*<!ENTITY/
-      IDENTITY = /^([!\*\w\-]+)(\s+#{NCNAME_STR})?(\s+["'](.*?)['"])?(\s+['"](.*?)["'])?/u
       ELEMENTDECL_START = /\A\s*<!ELEMENT/um
       ELEMENTDECL_PATTERN = /\A\s*(<!ELEMENT.*?)>/um
       SYSTEMENTITY = /\A\s*(%.*?;)\s*$/um
@@ -101,8 +99,9 @@ class BaseParser
       ENTITYDECL = /\s*(?:#{GEDECL})|(?:#{PEDECL})/um
 
       NOTATIONDECL_START = /\A\s*<!NOTATION/um
-      PUBLIC = /\A\s*<!NOTATION\s+#{NAME}\s+(PUBLIC)\s+#{PUBIDLITERAL}(?:\s+#{SYSTEMLITERAL})?\s*>/um
-      SYSTEM = /\A\s*<!NOTATION\s+#{NAME}\s+(SYSTEM)\s+#{SYSTEMLITERAL}\s*>/um
+      EXTERNAL_ID_PUBLIC = /\A\s*PUBLIC\s+#{PUBIDLITERAL}\s+#{SYSTEMLITERAL}\s*/um
+      EXTERNAL_ID_SYSTEM = /\A\s*SYSTEM\s+#{SYSTEMLITERAL}\s*/um
+      PUBLIC_ID = /\A\s*PUBLIC\s+#{PUBIDLITERAL}\s*/um
 
       EREFERENCE = /&(?!#{NAME};)/
 
@@ -225,24 +224,37 @@ def pull_event
           when INSTRUCTION_START
             return process_instruction
           when DOCTYPE_START
-            md = @source.match( DOCTYPE_PATTERN, true )
+            base_error_message = "Malformed DOCTYPE"
+            @source.match(DOCTYPE_START, true)
             @nsstack.unshift(curr_ns=Set.new)
-            identity = md[1]
-            close = md[2]
-            identity =~ IDENTITY
-            name = $1
-            raise REXML::ParseException.new("DOCTYPE is missing a name") if name.nil?
-            pub_sys = $2.nil? ? nil : $2.strip
-            long_name = $4.nil? ? nil : $4.strip
-            uri = $6.nil? ? nil : $6.strip
-            args = [ :start_doctype, name, pub_sys, long_name, uri ]
-            if close == ">"
+            name = parse_name(base_error_message)
+            if @source.match(/\A\s*\[/um, true)
+              id = [nil, nil, nil]
+              @document_status = :in_doctype
+            elsif @source.match(/\A\s*>/um, true)
+              id = [nil, nil, nil]
               @document_status = :after_doctype
-              @source.read if @source.buffer.size<2
-              md = @source.match(/^\s*/um, true)
-              @stack << [ :end_doctype ]
             else
-              @document_status = :in_doctype
+              id = parse_id(base_error_message,
+                            accept_external_id: true,
+                            accept_public_id: false)
+              if id[0] == "SYSTEM"
+                # For backward compatibility
+                id[1], id[2] = id[2], nil
+              end
+              if @source.match(/\A\s*\[/um, true)
+                @document_status = :in_doctype
+              elsif @source.match(/\A\s*>/um, true)
+                @document_status = :after_doctype
+              else
+                message = "#{base_error_message}: garbage after external ID"
+                raise REXML::ParseException.new(message, @source)
+              end
+            end
+            args = [:start_doctype, name, *id]
+            if @document_status == :after_doctype
+              @source.match(/\A\s*/um, true)
+              @stack << [ :end_doctype ]
             end
             return args
           when /^\s+/
@@ -313,27 +325,24 @@ def pull_event
             end
             return [ :attlistdecl, element, pairs, contents ]
           when NOTATIONDECL_START
-            md = nil
-            if @source.match( PUBLIC )
-              md = @source.match( PUBLIC, true )
-              pubid = system = nil
-              pubid_literal = md[3]
-              pubid = pubid_literal[1..-2] if pubid_literal # Remove quote
-              system_literal = md[4]
-              system = system_literal[1..-2] if system_literal # Remove quote
-              vals = [md[1], md[2], pubid, system]
-            elsif @source.match( SYSTEM )
-              md = @source.match( SYSTEM, true )
-              system = nil
-              system_literal = md[3]
-              system = system_literal[1..-2] if system_literal # Remove quote
-              vals = [md[1], md[2], nil, system]
-            else
-              details = notation_decl_invalid_details
-              message = "Malformed notation declaration: #{details}"
+            base_error_message = "Malformed notation declaration"
+            unless @source.match(/\A\s*<!NOTATION\s+/um, true)
+              if @source.match(/\A\s*<!NOTATION\s*>/um)
+                message = "#{base_error_message}: name is missing"
+              else
+                message = "#{base_error_message}: invalid declaration name"
+              end
+              raise REXML::ParseException.new(message, @source)
+            end
+            name = parse_name(base_error_message)
+            id = parse_id(base_error_message,
+                          accept_external_id: true,
+                          accept_public_id: true)
+            unless @source.match(/\A\s*>/um, true)
+              message = "#{base_error_message}: garbage before end >"
               raise REXML::ParseException.new(message, @source)
             end
-            return [ :notationdecl, *vals ]
+            return [:notationdecl, name, *id]
           when DOCTYPE_END
             @document_status = :after_doctype
             @source.match( DOCTYPE_END, true )
@@ -488,6 +497,85 @@ def need_source_encoding_update?(xml_declaration_encoding)
         true
       end
 
+      def parse_name(base_error_message)
+        md = @source.match(/\A\s*#{NAME}/um, true)
+        unless md
+          if @source.match(/\A\s*\S/um)
+            message = "#{base_error_message}: invalid name"
+          else
+            message = "#{base_error_message}: name is missing"
+          end
+          raise REXML::ParseException.new(message, @source)
+        end
+        md[1]
+      end
+
+      def parse_id(base_error_message,
+                   accept_external_id:,
+                   accept_public_id:)
+        if accept_external_id and (md = @source.match(EXTERNAL_ID_PUBLIC, true))
+          pubid = system = nil
+          pubid_literal = md[1]
+          pubid = pubid_literal[1..-2] if pubid_literal # Remove quote
+          system_literal = md[2]
+          system = system_literal[1..-2] if system_literal # Remove quote
+          ["PUBLIC", pubid, system]
+        elsif accept_public_id and (md = @source.match(PUBLIC_ID, true))
+          pubid = system = nil
+          pubid_literal = md[1]
+          pubid = pubid_literal[1..-2] if pubid_literal # Remove quote
+          ["PUBLIC", pubid, nil]
+        elsif accept_external_id and (md = @source.match(EXTERNAL_ID_SYSTEM, true))
+          system = nil
+          system_literal = md[1]
+          system = system_literal[1..-2] if system_literal # Remove quote
+          ["SYSTEM", nil, system]
+        else
+          details = parse_id_invalid_details(accept_external_id: accept_external_id,
+                                             accept_public_id: accept_public_id)
+          message = "#{base_error_message}: #{details}"
+          raise REXML::ParseException.new(message, @source)
+        end
+      end
+
+      def parse_id_invalid_details(accept_external_id:,
+                                   accept_public_id:)
+        public = /\A\s*PUBLIC/um
+        system = /\A\s*SYSTEM/um
+        if (accept_external_id or accept_public_id) and @source.match(/#{public}/um)
+          if @source.match(/#{public}(?:\s+[^'"]|\s*[\[>])/um)
+            return "public ID literal is missing"
+          end
+          unless @source.match(/#{public}\s+#{PUBIDLITERAL}/um)
+            return "invalid public ID literal"
+          end
+          if accept_public_id
+            if @source.match(/#{public}\s+#{PUBIDLITERAL}\s+[^'"]/um)
+              return "system ID literal is missing"
+            end
+            unless @source.match(/#{public}\s+#{PUBIDLITERAL}\s+#{SYSTEMLITERAL}/um)
+              return "invalid system literal"
+            end
+            "garbage after system literal"
+          else
+            "garbage after public ID literal"
+          end
+        elsif accept_external_id and @source.match(/#{system}/um)
+          if @source.match(/#{system}(?:\s+[^'"]|\s*[\[>])/um)
+            return "system literal is missing"
+          end
+          unless @source.match(/#{system}\s+#{SYSTEMLITERAL}/um)
+            return "invalid system literal"
+          end
+          "garbage after system literal"
+        else
+          unless @source.match(/\A\s*(?:PUBLIC|SYSTEM)\s/um)
+            return "invalid ID type"
+          end
+          "ID type is missing"
+        end
+      end
+
       def process_instruction
         match_data = @source.match(INSTRUCTION_PATTERN, true)
         unless match_data
@@ -580,42 +668,6 @@ def parse_attributes(prefixes, curr_ns)
         end
         return attributes, closed
       end
-
-      def notation_decl_invalid_details
-        name = /#{NOTATIONDECL_START}\s+#{NAME}/um
-        public = /#{name}\s+PUBLIC/um
-        system = /#{name}\s+SYSTEM/um
-        if @source.match(/#{NOTATIONDECL_START}\s*>/um)
-          return "name is missing"
-        elsif not @source.match(/#{name}[\s>]/um)
-          return "invalid name"
-        elsif @source.match(/#{name}\s*>/um)
-          return "ID type is missing"
-        elsif not @source.match(/#{name}\s+(?:PUBLIC|SYSTEM)[\s>]/um)
-          return "invalid ID type"
-        elsif @source.match(/#{public}/um)
-          if @source.match(/#{public}\s*>/um)
-            return "public ID literal is missing"
-          elsif not @source.match(/#{public}\s+#{PUBIDLITERAL}/um)
-            return "invalid public ID literal"
-          elsif @source.match(/#{public}\s+#{PUBIDLITERAL}[^\s>]/um)
-            return "garbage after public ID literal"
-          elsif not @source.match(/#{public}\s+#{PUBIDLITERAL}\s+#{SYSTEMLITERAL}/um)
-            return "invalid system literal"
-          elsif not @source.match(/#{public}\s+#{PUBIDLITERAL}\s+#{SYSTEMLITERAL}\s*>/um)
-            return "garbage after system literal"
-          end
-        elsif @source.match(/#{system}/um)
-          if @source.match(/#{system}\s*>/um)
-            return "system literal is missing"
-          elsif not @source.match(/#{system}\s+#{SYSTEMLITERAL}/um)
-            return "invalid system literal"
-          elsif not @source.match(/#{system}\s+#{SYSTEMLITERAL}\s*>/um)
-            return "garbage after system literal"
-          end
-        end
-        "end > is missing"
-      end
     end
   end
 end
diff --git a/test/parse/test_document_type_declaration.rb b/test/parse/test_document_type_declaration.rb
index 80f70888..55713909 100644
--- a/test/parse/test_document_type_declaration.rb
+++ b/test/parse/test_document_type_declaration.rb
@@ -5,17 +5,187 @@
 module REXMLTests
   class TestParseDocumentTypeDeclaration < Test::Unit::TestCase
     private
-    def xml(internal_subset)
-      <<-XML
-<!DOCTYPE r SYSTEM "urn:x-rexml:test" [
-#{internal_subset}
-]>
+    def parse(doctype)
+      REXML::Document.new(<<-XML).doctype
+#{doctype}
 <r/>
       XML
     end
 
-    def parse(internal_subset)
-      REXML::Document.new(xml(internal_subset)).doctype
+    class TestName < self
+      def test_valid
+        doctype = parse(<<-DOCTYPE)
+<!DOCTYPE r>
+        DOCTYPE
+        assert_equal("r", doctype.name)
+      end
+
+      def test_garbage_plus_before_name_at_line_start
+        exception = assert_raise(REXML::ParseException) do
+          parse(<<-DOCTYPE)
+<!DOCTYPE +
+r SYSTEM "urn:x-rexml:test" [
+]>
+          DOCTYPE
+        end
+        assert_equal(<<-DETAIL.chomp, exception.to_s)
+Malformed DOCTYPE: invalid name
+Line: 5
+Position: 51
+Last 80 unconsumed characters:
++ r SYSTEM "urn:x-rexml:test" [ ]>  <r/> 
+        DETAIL
+      end
+    end
+
+    class TestExternalID < self
+      class TestSystem < self
+        def test_left_bracket_in_system_literal
+          doctype = parse(<<-DOCTYPE)
+<!DOCTYPE r SYSTEM "urn:x-rexml:[test" [
+]>
+          DOCTYPE
+          assert_equal([
+                         "r",
+                         "SYSTEM",
+                         nil,
+                         "urn:x-rexml:[test",
+                       ],
+                       [
+                         doctype.name,
+                         doctype.external_id,
+                         doctype.public,
+                         doctype.system,
+                       ])
+        end
+
+        def test_greater_than_in_system_literal
+          doctype = parse(<<-DOCTYPE)
+<!DOCTYPE r SYSTEM "urn:x-rexml:>test" [
+]>
+          DOCTYPE
+          assert_equal([
+                         "r",
+                         "SYSTEM",
+                         nil,
+                         "urn:x-rexml:>test",
+                       ],
+                       [
+                         doctype.name,
+                         doctype.external_id,
+                         doctype.public,
+                         doctype.system,
+                       ])
+        end
+
+        def test_no_literal
+          exception = assert_raise(REXML::ParseException) do
+            parse(<<-DOCTYPE)
+<!DOCTYPE r SYSTEM>
+            DOCTYPE
+          end
+          assert_equal(<<-DETAIL.chomp, exception.to_s)
+Malformed DOCTYPE: system literal is missing
+Line: 3
+Position: 26
+Last 80 unconsumed characters:
+ SYSTEM>  <r/> 
+          DETAIL
+        end
+
+        def test_garbage_after_literal
+          exception = assert_raise(REXML::ParseException) do
+            parse(<<-DOCTYPE)
+<!DOCTYPE r SYSTEM 'r.dtd'x'>
+            DOCTYPE
+          end
+          assert_equal(<<-DETAIL.chomp, exception.to_s)
+Malformed DOCTYPE: garbage after external ID
+Line: 3
+Position: 36
+Last 80 unconsumed characters:
+x'>  <r/> 
+          DETAIL
+        end
+
+        def test_single_quote
+          doctype = parse(<<-DOCTYPE)
+<!DOCTYPE r SYSTEM 'r".dtd'>
+          DOCTYPE
+          assert_equal("r\".dtd", doctype.system)
+        end
+
+        def test_double_quote
+          doctype = parse(<<-DOCTYPE)
+<!DOCTYPE r SYSTEM "r'.dtd">
+          DOCTYPE
+          assert_equal("r'.dtd", doctype.system)
+        end
+      end
+
+      class TestPublic < self
+        class TestPublicIDLiteral < self
+          def test_content_double_quote
+            exception = assert_raise(REXML::ParseException) do
+              parse(<<-DOCTYPE)
+<!DOCTYPE r PUBLIC 'double quote " is invalid' "r.dtd">
+              DOCTYPE
+            end
+            assert_equal(<<-DETAIL.chomp, exception.to_s)
+Malformed DOCTYPE: invalid public ID literal
+Line: 3
+Position: 62
+Last 80 unconsumed characters:
+ PUBLIC 'double quote " is invalid' "r.dtd">  <r/> 
+            DETAIL
+          end
+
+          def test_single_quote
+            doctype = parse(<<-DOCTYPE)
+<!DOCTYPE r PUBLIC 'public-id-literal' "r.dtd">
+            DOCTYPE
+            assert_equal("public-id-literal", doctype.public)
+          end
+
+          def test_double_quote
+            doctype = parse(<<-DOCTYPE)
+<!DOCTYPE r PUBLIC "public'-id-literal" "r.dtd">
+            DOCTYPE
+            assert_equal("public'-id-literal", doctype.public)
+          end
+        end
+
+        class TestSystemLiteral < self
+          def test_garbage_after_literal
+            exception = assert_raise(REXML::ParseException) do
+              parse(<<-DOCTYPE)
+<!DOCTYPE r PUBLIC 'public-id-literal' 'system-literal'x'>
+              DOCTYPE
+            end
+            assert_equal(<<-DETAIL.chomp, exception.to_s)
+Malformed DOCTYPE: garbage after external ID
+Line: 3
+Position: 65
+Last 80 unconsumed characters:
+x'>  <r/> 
+           DETAIL
+          end
+
+          def test_single_quote
+            doctype = parse(<<-DOCTYPE)
+<!DOCTYPE r PUBLIC "public-id-literal" 'system"-literal'>
+            DOCTYPE
+            assert_equal("system\"-literal", doctype.system)
+          end
+
+          def test_double_quote
+            doctype = parse(<<-DOCTYPE)
+<!DOCTYPE r PUBLIC "public-id-literal" "system'-literal">
+            DOCTYPE
+            assert_equal("system'-literal", doctype.system)
+          end
+        end
+      end
     end
 
     class TestMixed < self
@@ -45,6 +215,15 @@ def test_notation_attlist
         assert_equal([REXML::NotationDecl, REXML::AttlistDecl],
                      doctype.children.collect(&:class))
       end
+
+      private
+      def parse(internal_subset)
+        super(<<-DOCTYPE)
+<!DOCTYPE r SYSTEM "urn:x-rexml:test" [
+#{internal_subset}
+]>
+        DOCTYPE
+      end
     end
   end
 end
diff --git a/test/parse/test_notation_declaration.rb b/test/parse/test_notation_declaration.rb
index fbd29e2a..19a0536d 100644
--- a/test/parse/test_notation_declaration.rb
+++ b/test/parse/test_notation_declaration.rb
@@ -50,7 +50,7 @@ def test_invalid_name
 Line: 5
 Position: 74
 Last 80 unconsumed characters:
- <!NOTATION '>  ]> <r/> 
+'>  ]> <r/> 
         DETAIL
       end
 
@@ -61,11 +61,11 @@ def test_no_id_type
           INTERNAL_SUBSET
         end
         assert_equal(<<-DETAIL.chomp, exception.to_s)
-Malformed notation declaration: ID type is missing
+Malformed notation declaration: invalid ID type
 Line: 5
 Position: 77
 Last 80 unconsumed characters:
- <!NOTATION name>  ]> <r/> 
+>  ]> <r/> 
         DETAIL
       end
 
@@ -80,7 +80,7 @@ def test_invalid_id_type
 Line: 5
 Position: 85
 Last 80 unconsumed characters:
- <!NOTATION name INVALID>  ]> <r/> 
+ INVALID>  ]> <r/> 
         DETAIL
       end
     end
@@ -98,7 +98,7 @@ def test_no_literal
 Line: 5
 Position: 84
 Last 80 unconsumed characters:
- <!NOTATION name SYSTEM>  ]> <r/> 
+ SYSTEM>  ]> <r/> 
           DETAIL
         end
 
@@ -109,11 +109,11 @@ def test_garbage_after_literal
             INTERNAL_SUBSET
           end
           assert_equal(<<-DETAIL.chomp, exception.to_s)
-Malformed notation declaration: garbage after system literal
+Malformed notation declaration: garbage before end >
 Line: 5
 Position: 103
 Last 80 unconsumed characters:
- <!NOTATION name SYSTEM 'system-literal'x'>  ]> <r/> 
+x'>  ]> <r/> 
           DETAIL
         end
 
@@ -145,7 +145,7 @@ def test_content_double_quote
 Line: 5
 Position: 129
 Last 80 unconsumed characters:
- <!NOTATION name PUBLIC 'double quote " is invalid' "system-literal">  ]> <r/> 
+ PUBLIC 'double quote " is invalid' "system-literal">  ]> <r/> 
             DETAIL
           end
 
@@ -172,11 +172,11 @@ def test_garbage_after_literal
               INTERNAL_SUBSET
             end
             assert_equal(<<-DETAIL.chomp, exception.to_s)
-Malformed notation declaration: garbage after system literal
+Malformed notation declaration: garbage before end >
 Line: 5
 Position: 123
 Last 80 unconsumed characters:
- <!NOTATION name PUBLIC 'public-id-literal' 'system-literal'x'>  ]> <r/> 
+x'>  ]> <r/> 
            DETAIL
           end
 
@@ -229,7 +229,7 @@ def test_no_literal
 Line: 5
 Position: 84
 Last 80 unconsumed characters:
- <!NOTATION name PUBLIC>  ]> <r/> 
+ PUBLIC>  ]> <r/> 
         DETAIL
       end
 
@@ -244,7 +244,7 @@ def test_literal_content_double_quote
 Line: 5
 Position: 128
 Last 80 unconsumed characters:
- <!NOTATION name PUBLIC 'double quote \" is invalid in PubidLiteral'>  ]> <r/> 
+ PUBLIC 'double quote \" is invalid in PubidLiteral'>  ]> <r/> 
         DETAIL
       end
 
@@ -255,11 +255,11 @@ def test_garbage_after_literal
           INTERNAL_SUBSET
         end
         assert_equal(<<-DETAIL.chomp, exception.to_s)
-Malformed notation declaration: garbage after public ID literal
+Malformed notation declaration: garbage before end >
 Line: 5
 Position: 106
 Last 80 unconsumed characters:
- <!NOTATION name PUBLIC 'public-id-literal'x'>  ]> <r/> 
+x'>  ]> <r/> 
         DETAIL
       end