diff --git a/compiler/nodes.py b/compiler/nodes.py
index b9918a1..c466edf 100644
--- a/compiler/nodes.py
+++ b/compiler/nodes.py
@@ -316,7 +316,7 @@ class Variable(Node):
 
     def semantic_analysis(self, context: semantic.Context):
         super(Variable, self).semantic_analysis(context)
-        variable = context.get_variable(self.identifier.value)
+        variable = context.get_variable(self.identifier.value, reader=self)
         if variable is None:
             raise SemanticAnalysisError(location=self.location(), message=f"Unknown variable '{self.identifier.value}'")
 
diff --git a/compiler/semantic.py b/compiler/semantic.py
index b55e8b3..702c19f 100644
--- a/compiler/semantic.py
+++ b/compiler/semantic.py
@@ -15,7 +15,11 @@ class SymbolABC(abc.ABC):
     def __init__(self, context: Context, name: str, value: nodes.Value | None | Literal["builtin"] = None):
         self.context = context
         self.name = name
-        self.definitions = [value]
+        self.writes: list[nodes.Node] = []
+        if isinstance(value, nodes.Node):
+            self.writes += [value]
+
+        self.reads: list[nodes.Node] = []
         self._repr_guard: bool = False
 
     def fully_qualified_name(self) -> str:
@@ -28,14 +32,15 @@ class SymbolABC(abc.ABC):
         if self._repr_guard:
             return str(self)
         self._repr_guard = True
-        definitions = [str(d.location().begin) for d in self.writes if isinstance(d, nodes.Node)]
+        writes = [str(d.location().begin) for d in self.writes]
+        reads = [str(d.location().begin) for d in self.reads]
         self._repr_guard = False
-        return f"{str(self)} [definitions: {', '.join(definitions)}]"
+        return f"{str(self)} [writes: {', '.join(writes)}; reads: {', '.join(reads)}]"
 
 
 class Type(SymbolABC):
     def __init__(self, context: Context, name: str, value: nodes.Value | None | Literal["builtin"] = None):
-        super().__init__(context, name, value)
+        super().__init__(context, name, value=value)
 
 
 class Function(Type):
@@ -44,8 +49,10 @@ class Function(Type):
 
 class Variable(SymbolABC):
     @typecheck
-    def __init__(self, context: Context, name: str, value: nodes.Value | None = None, typedef: Type | None = None):
-        super().__init__(context, name, value)
+    def __init__(self, context: Context, name: str,
+                 value: nodes.Value | None = None,
+                 typedef: Type | None = None):
+        super().__init__(context, name, value=value)
         self.type = typedef if typedef is not None else context.get_type("__unknown")
 
     def __str__(self):
@@ -82,10 +89,18 @@ class Context:
 
         return None
 
-    def get_variable(self, name: str) -> Variable | None:
-        return self._resolve_symbol("variables", name)
+    @typecheck
+    def _get_symbol(self, attribute_name: str, name: str, reader: nodes.Node | None = None) -> SymbolABC | None:
+        node = self._resolve_symbol(attribute_name, name)
+        if node is not None and reader is not None:
+            node.reads += [reader]
+        return node
 
-    def define_variable(self, name: str, type_identifier: nodes.Identifier, value: nodes.Value) -> Variable:
+    def get_variable(self, name: str, reader: nodes.Node | None = None) -> Variable | None:
+        return self._get_symbol("variables", name, reader)
+
+    def define_variable(self, name: str,
+                        type_identifier: nodes.Identifier, value: nodes.Value) -> Variable:
         if name in self.variables:
             raise SemanticAnalysisError(value.location())
 
@@ -94,7 +109,7 @@ class Context:
             raise SemanticAnalysisError(location=type_identifier.location(),
                                         message=f"Unknown type '{type_identifier.value}'")
 
-        variable = Variable(self, name, value, typedef)
+        variable = Variable(self, name, value=value, typedef=typedef)
 
         self.variables[name] = variable
 
@@ -107,7 +122,7 @@ class Context:
             raise SemanticAnalysisError(value.location(),
                                         message=f"Can't assign a value to undeclared variable '{name}'")
         variable = self.variables[name]
-        variable.definitions += [value]
+        variable.writes += [value]
 
         self.variables[name] = variable
 
@@ -118,17 +133,17 @@ class Context:
         typedef: Type
         if name in self.types:
             typedef = self.types[name]
-            typedef.definitions += [value]
+            typedef.writes += [value]
         else:
-            typedef = Type(self, name, value)
+            typedef = Type(self, name, value=value)
 
         self.types[name] = typedef
 
         return typedef
 
     @typecheck
-    def get_type(self, name: str) -> Type | None:
-        return self._resolve_symbol("types", name)
+    def get_type(self, name: str, reader: nodes.Node | None = None) -> Type | None:
+        return self._get_symbol("types", name, reader)
 
     def add_context(self, context: Context) -> None:
         self.child_contexts[context.name] = context
@@ -163,10 +178,10 @@ class BuiltinContext(Context):
     def __init__(self):
         super().__init__(name="builtins", parent=None)
         self.types = {
-            "__unknown": Type(self, "__unknown", "builtin"),
-            "__function": Function(self, "__function", "builtin"),
-            "uint32": Type(self, "uint32", "builtin")
+            "__unknown": Type(self, "__unknown", value="builtin"),
+            "__function": Function(self, "__function", value="builtin"),
+            "uint32": Type(self, "uint32", value="builtin")
         }
         self.variables = {
-            "display": Variable(self, "display", None, self.types["__function"])
+            "display": Variable(self, "display", typedef=self.types["__function"])
         }