diff --git a/BotSharp.NLP.UnitTest/DefaultTaggerTest.cs b/BotSharp.NLP.UnitTest/DefaultTaggerTest.cs
index 7f2d2f53..ac2aef22 100644
--- a/BotSharp.NLP.UnitTest/DefaultTaggerTest.cs
+++ b/BotSharp.NLP.UnitTest/DefaultTaggerTest.cs
@@ -14,22 +14,15 @@ namespace BotSharp.NLP.UnitTest
         [TestMethod]
         public void TagInCoNLL2000()
         {
-            var sentences = new CoNLLReader()
-                .Read(new ReaderOptions
-                {
-                    DataDir = AppDomain.CurrentDomain.BaseDirectory,
-                    FileName = "conll2000_chunking_train"
-                });
+            var tokenizer = new TokenizerFactory<RegexTokenizer>(new TokenizationOptions { }, SupportedLanguage.English);
+            var tokens = tokenizer.Tokenize("How are you doing?");
 
-            var tagger = new TaggerFactory<DefaultTagger>();
+            var tagger = new TaggerFactory<DefaultTagger>(new TagOptions
+            {
+                Tag = "NN"
+            }, SupportedLanguage.English);
 
-            // tokenize
-            
-            tagger.Tag(null,
-                new TagOptions
-                {
-                    
-                });
+            tagger.Tag(new Sentence { Words = tokens });
         }
     }
-}
+}
\ No newline at end of file
diff --git a/BotSharp.NLP.UnitTest/NGramTaggerTest.cs b/BotSharp.NLP.UnitTest/NGramTaggerTest.cs
new file mode 100644
index 00000000..befaa773
--- /dev/null
+++ b/BotSharp.NLP.UnitTest/NGramTaggerTest.cs
@@ -0,0 +1,46 @@
+using BotSharp.NLP.Corpus;
+using BotSharp.NLP.Tag;
+using BotSharp.NLP.Tokenize;
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+
+namespace BotSharp.NLP.UnitTest
+{
+    [TestClass]
+    public class NGramTaggerTest
+    {
+        [TestMethod]
+        public void TagInCoNLL2000()
+        {
+            // tokenization
+            var tokenizer = new TokenizerFactory<RegexTokenizer>(new TokenizationOptions
+            {
+                Pattern = RegexTokenizer.WORD_PUNC
+            }, SupportedLanguage.English);
+
+            var tokens = tokenizer.Tokenize("How are you doing?");
+
+            // get training corpus
+            string corpusDir = Environment.GetEnvironmentVariable("BOTSHARP_CORPUS_PATH", EnvironmentVariableTarget.User);
+            var sentences = new CoNLLReader()
+                .Read(new ReaderOptions
+                {
+                    DataDir = Path.Combine(corpusDir, "CoNLL"),
+                    FileName = "conll2000_chunking_train.txt"
+                });
+
+            // start tag
+            var tagger = new TaggerFactory<NGramTagger>(new TagOptions
+            {
+                NGram = 2,
+                Tag = "NN",
+                Corpus = sentences
+            }, SupportedLanguage.English);
+
+            tagger.Tag(new Sentence { Words = tokens });
+        }
+    }
+}
diff --git a/BotSharp.NLP.UnitTest/RegexStemmerTest.cs b/BotSharp.NLP.UnitTest/RegexStemmerTest.cs
index 9cc42c5f..8bf0fc98 100644
--- a/BotSharp.NLP.UnitTest/RegexStemmerTest.cs
+++ b/BotSharp.NLP.UnitTest/RegexStemmerTest.cs
@@ -12,13 +12,12 @@ namespace BotSharp.NLP.UnitTest
         [TestMethod]
         public void StemInDefault()
         {
-            var stemmer = new StemmerFactory<RegexStemmer>();
+            var stemmer = new StemmerFactory<RegexStemmer>(new StemOptions
+            {
+                Pattern = RegexStemmer.DEFAULT
+            }, SupportedLanguage.English);
 
-            var stem = stemmer.Stem("doing",
-                new StemOptions
-                {
-                    Pattern = RegexStemmer.DEFAULT
-                });
+            var stem = stemmer.Stem("doing");
 
             Assert.IsTrue(stem == "do");
         }
diff --git a/BotSharp.NLP.UnitTest/RegexTokenizerTest.cs b/BotSharp.NLP.UnitTest/RegexTokenizerTest.cs
index dbcc94c6..01b57429 100644
--- a/BotSharp.NLP.UnitTest/RegexTokenizerTest.cs
+++ b/BotSharp.NLP.UnitTest/RegexTokenizerTest.cs
@@ -9,13 +9,12 @@ namespace BotSharp.NLP.UnitTest
         [TestMethod]
         public void TokenizeInWhiteSpace()
         {
-            var tokenizer = new TokenizerFactory<RegexTokenizer>();
+            var tokenizer = new TokenizerFactory<RegexTokenizer>(new TokenizationOptions
+            {
+                Pattern = RegexTokenizer.WHITE_SPACE
+            }, SupportedLanguage.English);
 
-            var tokens = tokenizer.Tokenize("Chop into pieces, isn't it?",
-                new TokenizationOptions
-                {
-                    Pattern = RegexTokenizer.WHITE_SPACE
-                });
+            var tokens = tokenizer.Tokenize("Chop into pieces, isn't it?");
 
             Assert.IsTrue(tokens[0].Start == 0);
             Assert.IsTrue(tokens[0].Text == "Chop");
@@ -36,13 +35,12 @@ namespace BotSharp.NLP.UnitTest
         [TestMethod]
         public void TokenizeInWordPunctuation()
         {
-            var tokenizer = new TokenizerFactory<RegexTokenizer>();
+            var tokenizer = new TokenizerFactory<RegexTokenizer>(new TokenizationOptions
+            {
+                Pattern = RegexTokenizer.WORD_PUNC
+            }, SupportedLanguage.English);
 
-            var tokens = tokenizer.Tokenize("Chop into pieces, isn't it?",
-                new TokenizationOptions
-                {
-                    Pattern = RegexTokenizer.WORD_PUNC
-                });
+            var tokens = tokenizer.Tokenize("Chop into pieces, isn't it?");
 
             Assert.IsTrue(tokens[0].Start == 0);
             Assert.IsTrue(tokens[0].Text == "Chop");
@@ -75,17 +73,16 @@ namespace BotSharp.NLP.UnitTest
         [TestMethod]
         public void TokenizeInBlankLine()
         {
-            var tokenizer = new TokenizerFactory<RegexTokenizer>();
+            var tokenizer = new TokenizerFactory<RegexTokenizer>(new TokenizationOptions
+            {
+                Pattern = RegexTokenizer.BLANK_LINE
+            }, SupportedLanguage.English);
 
             var tokens = tokenizer.Tokenize(@"Chop into pieces, 
 
 isn't
 
-it?",
-                new TokenizationOptions
-                {
-                    Pattern = RegexTokenizer.BLANK_LINE
-                });
+it?");
 
             Assert.IsTrue(tokens[0].Start == 0);
             Assert.IsTrue(tokens[0].Text == "Chop into pieces,");
diff --git a/BotSharp.NLP/Corpus/CoNLL/README.md b/BotSharp.NLP/Corpus/CoNLL/README.md
index a5e05833..a1727e90 100644
--- a/BotSharp.NLP/Corpus/CoNLL/README.md
+++ b/BotSharp.NLP/Corpus/CoNLL/README.md
@@ -1 +1,2 @@
 conll2000_chunking is downloaded from https://www.clips.uantwerpen.be/conll2000/chunking/
+The train and test data consist of three columns separated by spaces. Each word has been put on a separate line and there is an empty line after each sentence. The first column contains the current word, the second its part-of-speech tag as derived by the Brill tagger and the third its chunk tag as derived from the WSJ corpus. 
\ No newline at end of file
diff --git a/BotSharp.NLP/Corpus/ConllReader.cs b/BotSharp.NLP/Corpus/ConllReader.cs
index 3a5754c4..ef971f4f 100644
--- a/BotSharp.NLP/Corpus/ConllReader.cs
+++ b/BotSharp.NLP/Corpus/ConllReader.cs
@@ -1,4 +1,5 @@
-using System;
+using BotSharp.NLP.Tokenize;
+using System;
 using System.Collections.Generic;
 using System.IO;
 using System.Text;
@@ -17,9 +18,36 @@ namespace BotSharp.NLP.Corpus
     {
         public List<Sentence> Read(ReaderOptions options)
         {
-            string corpus = File.ReadAllText(Path.Combine(options.DataDir, "conll2000_chunking_train.txt"));
+            var sentences = new List<Sentence>();
+            using(StreamReader reader = new StreamReader(Path.Combine(options.DataDir, options.FileName)))
+            {
+                string line = reader.ReadLine();
+                var sentence = new Sentence { Words = new List<Token> { } };
 
-            return null;
+                while (!reader.EndOfStream)
+                {
+                    if (String.IsNullOrEmpty(line))
+                    {
+                        sentences.Add(sentence);
+                        sentence = new Sentence { Words = new List<Token> { } };
+                    }
+                    else
+                    {
+                        var columns = line.Split(' ');
+
+                        sentence.Words.Add(new Token
+                        {
+                            Text = columns[0],
+                            Pos = columns[1]
+                        });
+                    }
+
+                    line = reader.ReadLine();
+                }
+                
+            }
+
+            return sentences;
         }
     }
 }
diff --git a/BotSharp.NLP/Stem/IStemmer.cs b/BotSharp.NLP/Stem/IStemmer.cs
index afd5ca55..6441039f 100644
--- a/BotSharp.NLP/Stem/IStemmer.cs
+++ b/BotSharp.NLP/Stem/IStemmer.cs
@@ -12,11 +12,6 @@ namespace BotSharp.NLP.Stem
     /// </summary>
     public interface IStemmer
     {
-        /// <summary>
-        /// Language
-        /// </summary>
-        SupportedLanguage Lang { get; set; }
-
         /// <summary>
         /// Strip affixes from the token and return the stem.
         /// </summary>
diff --git a/BotSharp.NLP/Stem/RegexStemmer.cs b/BotSharp.NLP/Stem/RegexStemmer.cs
index 23034418..d33c4fb7 100644
--- a/BotSharp.NLP/Stem/RegexStemmer.cs
+++ b/BotSharp.NLP/Stem/RegexStemmer.cs
@@ -15,8 +15,6 @@ namespace BotSharp.NLP.Stem
     {
         public const string DEFAULT = "ing$|s$|e$|able$";
 
-        public SupportedLanguage Lang { get; set; }
-
         private Regex _regex;
 
         public string Stem(string word, StemOptions options)
diff --git a/BotSharp.NLP/Stem/StemmerFactory.cs b/BotSharp.NLP/Stem/StemmerFactory.cs
index a94899ed..be7b4f70 100644
--- a/BotSharp.NLP/Stem/StemmerFactory.cs
+++ b/BotSharp.NLP/Stem/StemmerFactory.cs
@@ -14,16 +14,22 @@ namespace BotSharp.NLP.Stem
     /// <typeparam name="IStem"></typeparam>
     public class StemmerFactory<IStem> where IStem : IStemmer, new()
     {
+        private SupportedLanguage _lang { get; set; }
+
         private IStem _stemmer;
 
-        public StemmerFactory()
+        private StemOptions _options;
+
+        public StemmerFactory(StemOptions options, SupportedLanguage lang)
         {
+            _lang = lang;
+            _options = options;
             _stemmer = new IStem();
         }
 
-        public string Stem(string word, StemOptions options)
+        public string Stem(string word)
         {
-            return _stemmer.Stem(word, options);
+            return _stemmer.Stem(word, _options);
         }
     }
 }
diff --git a/BotSharp.NLP/Tag/DefaultTagger.cs b/BotSharp.NLP/Tag/DefaultTagger.cs
index 33bdcb72..48abb43c 100644
--- a/BotSharp.NLP/Tag/DefaultTagger.cs
+++ b/BotSharp.NLP/Tag/DefaultTagger.cs
@@ -12,16 +12,14 @@ namespace BotSharp.NLP.Tag
     /// </summary>
     public class DefaultTagger : ITagger
     {
-        public SupportedLanguage Lang { get; set; }
-
         public void Tag(Sentence sentence, TagOptions options)
         {
-            throw new NotImplementedException();
+            
         }
 
         public void Train(List<Sentence> sentences, TagOptions options)
         {
-            throw new NotImplementedException();
+            
         }
     }
 }
diff --git a/BotSharp.NLP/Tag/ITagger.cs b/BotSharp.NLP/Tag/ITagger.cs
index e204e666..71aa4ffb 100644
--- a/BotSharp.NLP/Tag/ITagger.cs
+++ b/BotSharp.NLP/Tag/ITagger.cs
@@ -11,11 +11,6 @@ namespace BotSharp.NLP.Tag
     /// </summary>
     public interface ITagger
     {
-        /// <summary>
-        /// Language
-        /// </summary>
-        SupportedLanguage Lang { get; set; }
-
         /// <summary>
         /// 
         /// </summary>
diff --git a/BotSharp.NLP/Tag/NGramTagger.cs b/BotSharp.NLP/Tag/NGramTagger.cs
index b386e932..42940869 100644
--- a/BotSharp.NLP/Tag/NGramTagger.cs
+++ b/BotSharp.NLP/Tag/NGramTagger.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using System.Text;
 using BotSharp.NLP.Tokenize;
 
@@ -11,16 +12,55 @@ namespace BotSharp.NLP.Tag
     /// </summary>
     public class NGramTagger : ITagger
     {
-        public SupportedLanguage Lang { get; set; }
+        public Dictionary<string, string> ContextMapping { get; set; }
 
         public void Tag(Sentence sentence, TagOptions options)
         {
-            throw new NotImplementedException();
+            // need training to generate model
+            if(ContextMapping == null)
+            {
+                var cache = new List<Tuple<String, String>>();
+                var contextTag = new List<Tuple<String, String, int>>();
+
+                ContextMapping = new Dictionary<string, string>();
+
+                options.Corpus.ForEach(sent =>
+                {
+                    // Supplementary place
+                    for (int ngram = 1; ngram < options.NGram; ngram++)
+                    {
+                        sent.Words.Insert(0, new Token { Text = "NIL", Pos = options.Tag, Start = (ngram - 1) * 3 });
+                    }
+
+                    int pos = options.NGram - 1;
+                    for(pos = 1; pos < sent.Words.Count; pos++)
+                    {
+                        Token pre = sent.Words[pos - 1];
+                        Token cur = sent.Words[pos];
+
+                        cache.Add(new Tuple<string, string>($"{pre.Pos} {cur.Text}", cur.Pos));// Dictionary.Add($"{pre.Pos} {cur.Text}", cur.Pos);
+                    }
+                });
+
+                var results = (from c in cache
+                               group c by c.Item1 into g
+                               select new { g.Key, Count = g.Count() }).ToList();
+
+                results.ForEach(x =>
+                {
+                    int count = cache.Count(c => c.Item1 == x.Key);
+                });
+            }
         }
 
         public void Train(List<Sentence> sentences, TagOptions options)
         {
             throw new NotImplementedException();
         }
+        
+        private class NGramFreq
+        {
+            public string Key { get; set; }
+        }
     }
 }
diff --git a/BotSharp.NLP/Tag/TagOptions.cs b/BotSharp.NLP/Tag/TagOptions.cs
index 2f6c7ea9..d33a395d 100644
--- a/BotSharp.NLP/Tag/TagOptions.cs
+++ b/BotSharp.NLP/Tag/TagOptions.cs
@@ -16,5 +16,15 @@ namespace BotSharp.NLP.Tag
         /// Used in DefaultTagger
         /// </summary>
         public string Tag { get; set; }
+
+        /// <summary>
+        /// N-Gram number
+        /// </summary>
+        public int NGram { get; set; }
+
+        /// <summary>
+        /// Tagged corpus used for training a model
+        /// </summary>
+        public List<Sentence> Corpus { get; set; }
     }
 }
diff --git a/BotSharp.NLP/Tag/TaggerFactory.cs b/BotSharp.NLP/Tag/TaggerFactory.cs
index 9b563d1c..1eba88f9 100644
--- a/BotSharp.NLP/Tag/TaggerFactory.cs
+++ b/BotSharp.NLP/Tag/TaggerFactory.cs
@@ -6,16 +6,22 @@ namespace BotSharp.NLP.Tag
 {
     public class TaggerFactory<ITag> where ITag : ITagger, new()
     {
+        private SupportedLanguage _lang;
+
         private ITag _tagger;
 
-        public TaggerFactory()
+        private TagOptions _options;
+
+        public TaggerFactory(TagOptions options, SupportedLanguage lang)
         {
+            _lang = lang;
+            _options = options;
             _tagger = new ITag();
         }
 
-        public void Tag(Sentence sentence, TagOptions options)
+        public void Tag(Sentence sentence)
         {
-            _tagger.Tag(sentence, options);
+            _tagger.Tag(sentence, _options);
         }
     }
 }
diff --git a/BotSharp.NLP/Tokenize/ITokenizer.cs b/BotSharp.NLP/Tokenize/ITokenizer.cs
index 1d761851..ca12b008 100644
--- a/BotSharp.NLP/Tokenize/ITokenizer.cs
+++ b/BotSharp.NLP/Tokenize/ITokenizer.cs
@@ -10,17 +10,12 @@ namespace BotSharp.NLP.Tokenize
     /// </summary>
     public interface ITokenizer
     {
-        /// <summary>
-        /// Language
-        /// </summary>
-        SupportedLanguage Lang { get; set; }
-
         /// <summary>
         /// Tokenize
         /// </summary>
         /// <param name="sentence">input sentence</param>
         /// <param name="options">Options such as: regex expression</param>
         /// <returns></returns>
-        Token[] Tokenize(string sentence, TokenizationOptions options);
+        List<Token> Tokenize(string sentence, TokenizationOptions options);
     }
 }
diff --git a/BotSharp.NLP/Tokenize/RegexTokenizer.cs b/BotSharp.NLP/Tokenize/RegexTokenizer.cs
index 791710d7..43cd2a2f 100644
--- a/BotSharp.NLP/Tokenize/RegexTokenizer.cs
+++ b/BotSharp.NLP/Tokenize/RegexTokenizer.cs
@@ -11,8 +11,6 @@ namespace BotSharp.NLP.Tokenize
     /// </summary>
     public class RegexTokenizer : ITokenizer
     {
-        public SupportedLanguage Lang { get; set; }
-
         /// <summary>
         /// Tokenize a text into a sequence of alphabetic and non-alphabetic characters
         /// </summary>
@@ -34,7 +32,7 @@ namespace BotSharp.NLP.Tokenize
 
         private Regex _regex;
 
-        public Token[] Tokenize(string sentence, TokenizationOptions options)
+        public List<Token> Tokenize(string sentence, TokenizationOptions options)
         {
             _regex = new Regex(options.Pattern);
 
@@ -65,7 +63,7 @@ namespace BotSharp.NLP.Tokenize
                     }
                 }
 
-                return tokens.ToArray();
+                return tokens.ToList();
             }
             else
             {
@@ -73,7 +71,7 @@ namespace BotSharp.NLP.Tokenize
                 {
                     Text = x.Value,
                     Start = x.Index
-                }).ToArray();
+                }).ToList();
             }
         }
     }
diff --git a/BotSharp.NLP/Tokenize/Token.cs b/BotSharp.NLP/Tokenize/Token.cs
index 43d8dd91..35f71d5e 100644
--- a/BotSharp.NLP/Tokenize/Token.cs
+++ b/BotSharp.NLP/Tokenize/Token.cs
@@ -55,5 +55,10 @@ namespace BotSharp.NLP.Tokenize
                 return Start + Text.Length - 1;
             }
         }
+
+        public override string ToString()
+        {
+            return $"{Text} {Start} {Pos}";
+        }
     }
 }
diff --git a/BotSharp.NLP/Tokenize/TokenizerFactory.cs b/BotSharp.NLP/Tokenize/TokenizerFactory.cs
index 78a2a416..3d841ce0 100644
--- a/BotSharp.NLP/Tokenize/TokenizerFactory.cs
+++ b/BotSharp.NLP/Tokenize/TokenizerFactory.cs
@@ -12,16 +12,22 @@ namespace BotSharp.NLP.Tokenize
     /// </summary>
     public class TokenizerFactory<ITokenize> where ITokenize : ITokenizer, new()
     {
+        private SupportedLanguage _lang;
+
         private ITokenize _tokenizer;
 
-        public TokenizerFactory()
+        private TokenizationOptions _options;
+
+        public TokenizerFactory(TokenizationOptions options, SupportedLanguage lang)
         {
+            _lang = lang;
+            _options = options;
             _tokenizer = new ITokenize();
         }
 
-        public Token[] Tokenize(string sentence, TokenizationOptions options)
+        public List<Token> Tokenize(string sentence)
         {
-            return _tokenizer.Tokenize(sentence, options);
+            return _tokenizer.Tokenize(sentence, _options);
         }
     }
 }