diff --git a/src/SVM.Assembler.Core/ISADefinition.cs b/src/SVM.Assembler.Core/ISADefinition.cs
index 0ca0e1d..7739544 100644
--- a/src/SVM.Assembler.Core/ISADefinition.cs
+++ b/src/SVM.Assembler.Core/ISADefinition.cs
@@ -4,6 +4,7 @@ using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using System.Xml;
+using System.Xml.Linq;
 using System.Xml.Serialization;
 
 namespace SVM.Assembler.Core
@@ -18,7 +19,7 @@ namespace SVM.Assembler.Core
 		{
 			foreach (var item in InstructionDefinitions)
 			{
-				foreach (var alias in item.Value.aliases)
+				foreach (var alias in item.Value.Aliases)
 				{
 					if (!InstructionDefinitionAliases.TryAdd(alias, item.Value))
 					{
@@ -57,13 +58,77 @@ namespace SVM.Assembler.Core
 				}
 			}
 		}
+		static bool ParseDefinition(XmlNode node, ref ISADefinition definition)
+		{
+
+			InstructionDefinition instDefinition = new InstructionDefinition();
+			foreach (XmlNode item in node.ChildNodes)
+			{
+				switch (item.Name)
+				{
+					case "Aliases":
+						foreach (XmlNode aliasNode in item.ChildNodes)
+						{
+							if (aliasNode.Name == "Alias")
+							{
+								instDefinition.Aliases.Add(aliasNode.Attributes["Name"].Value);
+							}
+							else
+							{
+								return false;
+							}
+						}
+						break;
+					case "Parameters":
+
+						break;
+					default:
+						break;
+				}
+				if (item.Name != "InstructionDefinition")
+				{
+					return false;
+				}
+			}
+			return true;
+		}
+		static bool ParseDefinitions(XmlNode node, ref ISADefinition definition)
+		{
+			foreach (XmlNode item in node.ChildNodes)
+			{
+				if (item.Name != "InstructionDefinition")
+				{
+					return false;
+				}
+				if (ParseDefinition(node, ref definition) == false)
+				{
+					return false;
+				}
+			}
+			return true;
+		}
 		public static bool TryParse(Stream inputStream, [MaybeNullWhen(false)] out ISADefinition definition)
 		{
 			XmlDocument xmlDocument = new XmlDocument();
 			xmlDocument.Load(inputStream);
+			ISADefinition isaDefinition = new ISADefinition();
 			foreach (XmlNode item in xmlDocument.ChildNodes)
 			{
 				ShowNode(item, 0);
+				switch (item.Name)
+				{
+					case "Enums":
+						break;
+					case "Definitions":
+						if (ParseDefinitions(item, ref isaDefinition) == false)
+						{
+							definition = null;
+							return false;
+						}
+						break;
+					default:
+						break;
+				}
 			}
 			definition = null;
 			return false;
diff --git a/src/SVM.Assembler.Core/InstructionDefinition.cs b/src/SVM.Assembler.Core/InstructionDefinition.cs
index 4b96e9a..b78b4a9 100644
--- a/src/SVM.Assembler.Core/InstructionDefinition.cs
+++ b/src/SVM.Assembler.Core/InstructionDefinition.cs
@@ -8,7 +8,7 @@ namespace SVM.Assembler.Core
 	public class InstructionDefinition
 	{
 		public PrimaryInstruction PrimaryInstruction = PrimaryInstruction.Nop;
-		public List<string> aliases = new List<string>();
+		public List<string> Aliases = new List<string>();
 		public List<InstructionParameter> ParameterPattern = new List<InstructionParameter>();
 	}
 }
diff --git a/src/SVM.Assembler/ISA.xml b/src/SVM.Assembler/ISA.xml
index acc5b07..61d774c 100644
--- a/src/SVM.Assembler/ISA.xml
+++ b/src/SVM.Assembler/ISA.xml
@@ -1,46 +1,48 @@
 <ISARoot>
 	<Enums>
 	</Enums>
-	<InstructionDefinition PrimaryInstruction="BMath">
-		<aliases>
-			<alias name="bmath"/>
-			<alias name="b.math"/>
-			<alias name="math.b"/>
-		</aliases>
-		<Parameters>
-			<InstructionParameter>
-				<AllowedIds>
-					<Text content="String"/>
-				</AllowedIds>
-				<ExpectedValue Type="Byte" Pos="1" Converter="InternalEnum:bOp" />
-			</InstructionParameter>
-			<InstructionParameter>
-				<AllowedIds>
-					<Text content="String"/>
-				</AllowedIds>
-				<ExpectedValue Type="Byte" Pos="2" Converter="InternalEnum:NativeType" />
-			</InstructionParameter>
-			<InstructionParameter>
-				<AllowedIds>
-					<Text content="String"/>
-					<Text content="Register"/>
-				</AllowedIds>
-				<ExpectedValue Type="Byte" Pos="3" Converter="Register" />
-			</InstructionParameter>
-			<InstructionParameter>
-				<AllowedIds>
-					<Text content="String"/>
-					<Text content="Register"/>
-				</AllowedIds>
-				<ExpectedValue Type="Byte" Pos="4" Converter="Register" />
-			</InstructionParameter>
-			<InstructionParameter>
-				<AllowedIds>
-					<Text content="String"/>
-					<Text content="Register"/>
-				</AllowedIds>
-				<ExpectedValue Type="Byte" Pos="5" Converter="Register" />
-			</InstructionParameter>
-		</Parameters>
-	</InstructionDefinition>
+	<Definitions>
+		<InstructionDefinition PrimaryInstruction="BMath">
+			<Aliases>
+				<Alias Name="bmath"/>
+				<Alias Name="b.math"/>
+				<Alias Name="math.b"/>
+			</Aliases>
+			<Parameters>
+				<InstructionParameter>
+					<MatchingItems>
+						<Item Id="String"/>
+					</MatchingItems>
+					<ExpectedValue Type="Byte" Pos="1" Converter="InternalEnum:bOp" />
+				</InstructionParameter>
+				<InstructionParameter>
+					<MatchingItems>
+						<Item Id="String"/>
+					</MatchingItems>
+					<ExpectedValue Type="Byte" Pos="2" Converter="InternalEnum:NativeType" />
+				</InstructionParameter>
+				<InstructionParameter>
+					<MatchingItems>
+						<Item Id="String"/>
+						<Item Id="Register"/>
+					</MatchingItems>
+					<ExpectedValue Type="Byte" Pos="3" Converter="Register" />
+				</InstructionParameter>
+				<InstructionParameter>
+					<MatchingItems>
+						<Item Id="String"/>
+						<Item Id="Register"/>
+					</MatchingItems>
+					<ExpectedValue Type="Byte" Pos="4" Converter="Register" />
+				</InstructionParameter>
+				<InstructionParameter>
+					<MatchingItems>
+						<Item Id="String"/>
+						<Item Id="Register"/>
+					</MatchingItems>
+					<ExpectedValue Type="Byte" Pos="5" Converter="Register" />
+				</InstructionParameter>
+			</Parameters>
+		</InstructionDefinition>
+	</Definitions>
 </ISARoot>
\ No newline at end of file