diff --git a/LanguageServer/src/main/java/org/nittalab/dtram/languageserver/model/Keywords.java b/LanguageServer/src/main/java/org/nittalab/dtram/languageserver/model/Keywords.java
new file mode 100644
index 0000000..76d7d1d
--- /dev/null
+++ b/LanguageServer/src/main/java/org/nittalab/dtram/languageserver/model/Keywords.java
@@ -0,0 +1,17 @@
+package org.nittalab.dtram.languageserver.model;
+
+/**
+ * {@link Keywords} class holds all keywords used in DTRAM.
+ *
+ * @author Shohei Yamagiwa
+ * @since 0.1
+ */
+public class Keywords {
+    public static final String CHANNEL = "channel";
+    public static final String INIT = "init";
+    public static final String IN = "in";
+    public static final String OUT = "out";
+    public static final String REF = "ref";
+    public static final String SUB_CHANNEL = "sub";
+    public static final String NATIVE = "native";
+}
diff --git a/LanguageServer/src/main/java/org/nittalab/dtram/languageserver/model/Operators.java b/LanguageServer/src/main/java/org/nittalab/dtram/languageserver/model/Operators.java
new file mode 100644
index 0000000..cf8a4f4
--- /dev/null
+++ b/LanguageServer/src/main/java/org/nittalab/dtram/languageserver/model/Operators.java
@@ -0,0 +1,45 @@
+package org.nittalab.dtram.languageserver.model;
+
+/**
+ * {@link Operators} class holds all operators used in DTRAM.
+ *
+ * @author Shohei Yamagiwa
+ * @since 0.1
+ */
+public class Operators {
+    /**
+     * Unary operators
+     */
+    public static final String MINUS = "-";
+
+    /**
+     * Arithmetic operators
+     */
+    public static final String ADD = "+";
+    public static final String SUB = "-";
+    public static final String MUL = "*";
+    public static final String DIV = "/";
+    public static final String MOD = "%";
+
+    /**
+     * Rational operators
+     */
+    public static final String EQ = "==";
+    public static final String NEQ = "!=";
+    public static final String GT = ">";
+    public static final String LT = "<";
+    public static final String GE = ">=";
+    public static final String LE = "<=";
+
+    /**
+     * Logical operators
+     */
+    public static final String AND = "&&";
+    public static final String OR = "||";
+    public static final String NEG = "!";
+
+    /**
+     * Assignment operators
+     */
+    public static final String ASSIGNMENT = "=";
+}
diff --git a/LanguageServer/src/main/java/org/nittalab/dtram/languageserver/model/Tokens.java b/LanguageServer/src/main/java/org/nittalab/dtram/languageserver/model/Tokens.java
index c5852ea..9d1a9c8 100644
--- a/LanguageServer/src/main/java/org/nittalab/dtram/languageserver/model/Tokens.java
+++ b/LanguageServer/src/main/java/org/nittalab/dtram/languageserver/model/Tokens.java
@@ -9,14 +9,6 @@
 public class Tokens {
     public static final String SPACE = " ";
 
-    public static final String CHANNEL = "channel";
-    public static final String INIT = "init";
-    public static final String IN = "in";
-    public static final String OUT = "out";
-    public static final String REF = "ref";
-    public static final String SUB_CHANNEL = "sub";
-    public static final String NATIVE = "native";
-
     public static final String LEFT_CURLY_BRACKET = "{";
     public static final String RIGHT_CURLY_BRACKET = "}";
     public static final String LEFT_BRACKET = "(";
@@ -24,26 +16,7 @@
     public static final String LEFT_SQUARE_BRACKET = "[";
     public static final String RIGHT_SQUARE_BRACKET = "]";
 
-    public static final String ADD = "+";
-    public static final String SUB = "-";
-    public static final String MUL = "*";
-    public static final String DIV = "/";
-    public static final String MOD = "%";
-
-    public static final String MINUS = "-";
-
-    public static final String EQ = "==";
-    public static final String NEQ = "!=";
-    public static final String GT = ">";
-    public static final String LT = "<";
-    public static final String GE = ">=";
-    public static final String LE = "<=";
-    public static final String AND = "&&";
-    public static final String OR = "||";
-    public static final String NEG = "!";
-
     public static final String EQUALS = "=";
-    public static final String ASSIGNMENT = "=";
     public static final String COMMA = ",";
     public static final String COLON = ":";
     public static final String DOT = ".";
diff --git a/LanguageServer/src/main/java/org/nittalab/dtram/languageserver/utils/Tokenizer.java b/LanguageServer/src/main/java/org/nittalab/dtram/languageserver/utils/Tokenizer.java
index 9598c82..387303c 100644
--- a/LanguageServer/src/main/java/org/nittalab/dtram/languageserver/utils/Tokenizer.java
+++ b/LanguageServer/src/main/java/org/nittalab/dtram/languageserver/utils/Tokenizer.java
@@ -1,5 +1,6 @@
 package org.nittalab.dtram.languageserver.utils;
 
+import org.nittalab.dtram.languageserver.model.Operators;
 import org.nittalab.dtram.languageserver.model.Position;
 import org.nittalab.dtram.languageserver.model.Token;
 import org.nittalab.dtram.languageserver.model.Tokens;
@@ -45,12 +46,23 @@
         tokens = extractMultilineComments(tokens);
         tokens = extractComments(tokens);
 
-        tokens = splitTokens(tokens, Tokens.EQ);
-        tokens = splitTokens(tokens, Tokens.NEQ);
-        tokens = splitTokens(tokens, Tokens.GE);
-        tokens = splitTokens(tokens, Tokens.LE);
-        tokens = splitTokens(tokens, Tokens.AND);
-        tokens = splitTokens(tokens, Tokens.OR);
+        tokens = splitTokens(tokens, Operators.EQ);
+        tokens = splitTokens(tokens, Operators.NEQ);
+        tokens = splitTokens(tokens, Operators.GE);
+        tokens = splitTokens(tokens, Operators.LE);
+        tokens = splitTokens(tokens, Operators.AND);
+        tokens = splitTokens(tokens, Operators.OR);
+
+        tokens = splitTokens(tokens, Operators.ADD);
+        tokens = splitTokens(tokens, Operators.SUB);
+        tokens = splitTokens(tokens, Operators.MUL);
+        tokens = splitTokens(tokens, Operators.DIV);
+        tokens = splitTokens(tokens, Operators.MOD);
+        tokens = splitTokens(tokens, Operators.MINUS);
+        tokens = splitTokens(tokens, Operators.GT);
+        tokens = splitTokens(tokens, Operators.LT);
+        tokens = splitTokens(tokens, Operators.NEG);
+        tokens = splitTokens(tokens, Operators.ASSIGNMENT);
 
         tokens = splitTokens(tokens, Tokens.LEFT_BRACKET);
         tokens = splitTokens(tokens, Tokens.RIGHT_BRACKET);
@@ -59,20 +71,7 @@
         tokens = splitTokens(tokens, Tokens.LEFT_SQUARE_BRACKET);
         tokens = splitTokens(tokens, Tokens.RIGHT_SQUARE_BRACKET);
 
-        tokens = splitTokens(tokens, Tokens.ADD);
-        tokens = splitTokens(tokens, Tokens.SUB);
-        tokens = splitTokens(tokens, Tokens.MUL);
-        tokens = splitTokens(tokens, Tokens.DIV);
-        tokens = splitTokens(tokens, Tokens.MOD);
-
-        tokens = splitTokens(tokens, Tokens.MINUS);
-
-        tokens = splitTokens(tokens, Tokens.GT);
-        tokens = splitTokens(tokens, Tokens.LT);
-        tokens = splitTokens(tokens, Tokens.NEG);
-
         tokens = splitTokens(tokens, Tokens.EQUALS);
-        tokens = splitTokens(tokens, Tokens.ASSIGNMENT);
         tokens = splitTokens(tokens, Tokens.COLON);
         tokens = splitTokens(tokens, Tokens.COMMA);
         tokens = splitTokens(tokens, Tokens.DOT);