query expression and data source handler

LINQ/LINQ/Interpreter/Query/AggregateExpression.vb

@@ -1,6 +1,6 @@
 Namespace Interpreter.Query
 
-    Public Class AggregateExpression
+    Public Class AggregateExpression : Inherits QueryExpression
 
     End Class
 End Namespace

LINQ/LINQ/Interpreter/Query/DataSoruce.vb

@@ -0,0 +1,25 @@
+Imports LINQ.Interpreter.Expressions
+Imports LINQ.Runtime
+
+Namespace Interpreter.Query
+
+    Public MustInherit Class DataSet
+
+        Public MustOverride Function PopulatesData(source As Object, driver As SymbolReference, env As Environment) As IEnumerable(Of Object)
+
+    End Class
+
+    Public Class SymbolIterator : Inherits DataSet
+
+        Public Overrides Function PopulatesData(source As Object, driver As SymbolReference, env As Environment) As IEnumerable(Of Object)
+            Throw New NotImplementedException()
+        End Function
+    End Class
+
+    Public Class URIIteratorDriver : Inherits DataSet
+
+        Public Overrides Function PopulatesData(source As Object, driver As SymbolReference, env As Environment) As IEnumerable(Of Object)
+            Throw New NotImplementedException()
+        End Function
+    End Class
+End Namespace

LINQ/LINQ/Interpreter/Query/ProjectionExpression.vb

@@ -1,6 +1,6 @@
 Namespace Interpreter.Query
 
-    Public Class ProjectionExpression
+    Public Class ProjectionExpression : Inherits QueryExpression
 
     End Class
 End Namespace

LINQ/LINQ/Interpreter/Query/Query.vb

@@ -0,0 +1,6 @@
+Namespace Interpreter.Query
+
+    Public MustInherit Class QueryExpression
+
+    End Class
+End Namespace

LINQ/LINQ/LINQ.vbproj

@@ -90,6 +90,8 @@
     <Compile Include="Interpreter\Expressions\BinaryExpression.vb" />
     <Compile Include="Interpreter\Expressions\ArrayExpression.vb" />
     <Compile Include="Interpreter\Query\AggregateExpression.vb" />
+    <Compile Include="Interpreter\Query\Query.vb" />
+    <Compile Include="Interpreter\Query\DataSoruce.vb" />
     <Compile Include="Interpreter\Query\ProjectionExpression.vb" />
     <Compile Include="Interpreter\Expressions\Literals.vb" />
     <Compile Include="Interpreter\Expressions\SymbolReference.vb" />