diff --git a/composer.json b/composer.json
index 023b021..468c292 100644
--- a/composer.json
+++ b/composer.json
@@ -37,7 +37,10 @@
         "psr-4": {
             "LanguageServer\\": "src/"
         },
-        "files" : ["src/utils.php"]
+        "files" : [
+            "src/utils.php",
+            "src/Fqn.php"
+        ]
     },
     "autoload-dev": {
         "psr-4": {
diff --git a/src/Fqn.php b/src/Fqn.php
new file mode 100644
index 0000000..25e59ae
--- /dev/null
+++ b/src/Fqn.php
@@ -0,0 +1,245 @@
+<?php
+
+/**
+ * Contains pure functions for converting AST nodes from and to FQNs
+ *
+ * Examples of FQNs:
+ *  - testFunction()
+ *  - TestNamespace\TestClass
+ *  - TestNamespace\TestClass::TEST_CONSTANT
+ *  - TestNamespace\TestClass::staticTestProperty
+ *  - TestNamespace\TestClass::testProperty
+ *  - TestNamespace\TestClass::staticTestMethod()
+ *  - TestNamespace\TestClass::testMethod()
+ */
+
+namespace LanguageServer\Fqn;
+
+use PhpParser\Node;
+
+/**
+ * Returns the FQN that is referenced by a node
+ *
+ * @param Node $node
+ * @return string|null
+ */
+function getReferencedFqn(Node $node)
+{
+    $parent = $node->getAttribute('parentNode');
+
+    if (
+        $node instanceof Node\Name && (
+            $parent instanceof Node\Stmt\ClassLike
+            || $parent instanceof Node\Param
+            || $parent instanceof Node\Stmt\Function_
+            || $parent instanceof Node\Expr\StaticCall
+            || $parent instanceof Node\Expr\ClassConstFetch
+            || $parent instanceof Node\Expr\StaticPropertyFetch
+        )
+    ) {
+        // For extends, implements, type hints and classes of classes of static calls use the name directly
+        $name = (string)$node;
+    // Only the name node should be considered a reference, not the UseUse node itself
+    } else if ($parent instanceof Node\Stmt\UseUse) {
+        $name = (string)$parent->name;
+        $grandParent = $parent->getAttribute('parentNode');
+        if ($grandParent instanceof Node\Stmt\GroupUse) {
+            $name = $grandParent->prefix . '\\' . $name;
+        }
+    // Only the name node should be considered a reference, not the New_ node itself
+    } else if ($parent instanceof Node\Expr\New_) {
+        if (!($parent->class instanceof Node\Name)) {
+            // Cannot get definition of dynamic calls
+            return null;
+        }
+        $name = (string)$parent->class;
+    } else if ($node instanceof Node\Expr\MethodCall || $node instanceof Node\Expr\PropertyFetch) {
+        if ($node->name instanceof Node\Expr || !($node->var instanceof Node\Expr\Variable)) {
+            // Cannot get definition of dynamic calls
+            return null;
+        }
+        // Need to resolve variable to a class
+        if ($node->var->name === 'this') {
+            // $this resolved to the class it is contained in
+            $n = $node;
+            while ($n = $n->getAttribute('parentNode')) {
+                if ($n instanceof Node\Stmt\Class_) {
+                    if ($n->isAnonymous()) {
+                        return null;
+                    }
+                    $name = (string)$n->namespacedName;
+                    break;
+                }
+            }
+            if (!isset($name)) {
+                return null;
+            }
+        } else {
+            // Other variables resolve to their definition
+            $varDef = getVariableDefinition($node->var);
+            if (!isset($varDef)) {
+                return null;
+            }
+            if ($varDef instanceof Node\Param) {
+                if (!isset($varDef->type)) {
+                    // Cannot resolve to class without a type hint
+                    // TODO: parse docblock
+                    return null;
+                }
+                $name = (string)$varDef->type;
+            } else if ($varDef instanceof Node\Expr\Assign) {
+                if ($varDef->expr instanceof Node\Expr\New_) {
+                    if (!($varDef->expr->class instanceof Node\Name)) {
+                        // Cannot get definition of dynamic calls
+                        return null;
+                    }
+                    $name = (string)$varDef->expr->class;
+                } else {
+                    return null;
+                }
+            } else {
+                return null;
+            }
+        }
+        $name .= '::' . (string)$node->name;
+    } else if ($parent instanceof Node\Expr\FuncCall) {
+        if ($parent->name instanceof Node\Expr) {
+            return null;
+        }
+        $name = (string)($node->getAttribute('namespacedName') ?? $parent->name);
+    } else if ($parent instanceof Node\Expr\ConstFetch) {
+        $name = (string)($node->getAttribute('namespacedName') ?? $parent->name);
+    } else if (
+        $node instanceof Node\Expr\ClassConstFetch
+        || $node instanceof Node\Expr\StaticPropertyFetch
+        || $node instanceof Node\Expr\StaticCall
+    ) {
+        if ($node->class instanceof Node\Expr || $node->name instanceof Node\Expr) {
+            // Cannot get definition of dynamic names
+            return null;
+        }
+        $className = (string)$node->class;
+        if ($className === 'self' || $className === 'static' || $className === 'parent') {
+            // self and static are resolved to the containing class
+            $n = $node;
+            while ($n = $n->getAttribute('parentNode')) {
+                if ($n instanceof Node\Stmt\Class_) {
+                    if ($n->isAnonymous()) {
+                        return null;
+                    }
+                    if ($className === 'parent') {
+                        // parent is resolved to the parent class
+                        if (!isset($n->extends)) {
+                            return null;
+                        }
+                        $className = (string)$n->extends;
+                    } else {
+                        $className = (string)$n->namespacedName;
+                    }
+                    break;
+                }
+            }
+        }
+        $name = (string)$className . '::' . $node->name;
+    } else {
+        return null;
+    }
+    if (
+        $node instanceof Node\Expr\MethodCall
+        || $node instanceof Node\Expr\StaticCall
+        || $parent instanceof Node\Expr\FuncCall
+    ) {
+        $name .= '()';
+    }
+    if (!isset($name)) {
+        return null;
+    }
+    return $name;
+}
+
+/**
+ * Returns the assignment or parameter node where a variable was defined
+ *
+ * @param Node\Expr\Variable $n The variable access
+ * @return Node\Expr\Assign|Node\Param|Node\Expr\ClosureUse|null
+ */
+function getVariableDefinition(Node\Expr\Variable $var)
+{
+    $n = $var;
+    // Traverse the AST up
+    do {
+        // If a function is met, check the parameters and use statements
+        if ($n instanceof Node\FunctionLike) {
+            foreach ($n->getParams() as $param) {
+                if ($param->name === $var->name) {
+                    return $param;
+                }
+            }
+            // If it is a closure, also check use statements
+            if ($n instanceof Node\Expr\Closure) {
+                foreach ($n->uses as $use) {
+                    if ($use->var === $var->name) {
+                        return $use;
+                    }
+                }
+            }
+            break;
+        }
+        // Check each previous sibling node for a variable assignment to that variable
+        while ($n->getAttribute('previousSibling') && $n = $n->getAttribute('previousSibling')) {
+            if ($n instanceof Node\Expr\Assign && $n->var instanceof Node\Expr\Variable && $n->var->name === $var->name) {
+                return $n;
+            }
+        }
+    } while (isset($n) && $n = $n->getAttribute('parentNode'));
+    // Return null if nothing was found
+    return null;
+}
+
+/**
+ * Returns the fully qualified name (FQN) that is defined by a node
+ *
+ * @param Node $node
+ * @return string|null
+ */
+function getDefinedFqn(Node $node)
+{
+    // Anonymous classes don't count as a definition
+    if ($node instanceof Node\Stmt\ClassLike && isset($node->name)) {
+        // Class, interface or trait declaration
+        return (string)$node->namespacedName;
+    } else if ($node instanceof Node\Stmt\Function_) {
+        // Function: use functionName() as the name
+        return (string)$node->namespacedName . '()';
+    } else if ($node instanceof Node\Stmt\ClassMethod) {
+        // Class method: use ClassName::methodName() as name
+        $class = $node->getAttribute('parentNode');
+        if (!isset($class->name)) {
+            // Ignore anonymous classes
+            return null;
+        }
+        return (string)$class->namespacedName . '::' . (string)$node->name . '()';
+    } else if ($node instanceof Node\Stmt\PropertyProperty) {
+        // Property: use ClassName::propertyName as name
+        $class = $node->getAttribute('parentNode')->getAttribute('parentNode');
+        if (!isset($class->name)) {
+            // Ignore anonymous classes
+            return null;
+        }
+        return (string)$class->namespacedName . '::' . (string)$node->name;
+    } else if ($node instanceof Node\Const_) {
+        $parent = $node->getAttribute('parentNode');
+        if ($parent instanceof Node\Stmt\Const_) {
+            // Basic constant: use CONSTANT_NAME as name
+            return (string)$node->namespacedName;
+        }
+        if ($parent instanceof Node\Stmt\ClassConst) {
+            // Class constant: use ClassName::CONSTANT_NAME as name
+            $class = $parent->getAttribute('parentNode');
+            if (!isset($class->name) || $class->name instanceof Node\Expr) {
+                return null;
+            }
+            return (string)$class->namespacedName . '::' . $node->name;
+        }
+    }
+}
diff --git a/src/NodeVisitor/DefinitionCollector.php b/src/NodeVisitor/DefinitionCollector.php
index 9032155..f902fbf 100644
--- a/src/NodeVisitor/DefinitionCollector.php
+++ b/src/NodeVisitor/DefinitionCollector.php
@@ -4,6 +4,7 @@ declare(strict_types = 1);
 namespace LanguageServer\NodeVisitor;
 
 use PhpParser\{NodeVisitorAbstract, Node};
+use function LanguageServer\Fqn\getDefinedFqn;
 
 /**
  * Collects definitions of classes, interfaces, traits, methods, properties and constants
@@ -20,7 +21,7 @@ class DefinitionCollector extends NodeVisitorAbstract
 
     public function enterNode(Node $node)
     {
-        $fqn = $node->getAttribute('ownerDocument')->getDefinedFqn($node);
+        $fqn = getDefinedFqn($node);
         if ($fqn !== null) {
             $this->definitions[$fqn] = $node;
         }
diff --git a/src/NodeVisitor/ReferencesCollector.php b/src/NodeVisitor/ReferencesCollector.php
index 749f635..08b660d 100644
--- a/src/NodeVisitor/ReferencesCollector.php
+++ b/src/NodeVisitor/ReferencesCollector.php
@@ -3,6 +3,7 @@ declare(strict_types = 1);
 
 namespace LanguageServer\NodeVisitor;
 
+use function LanguageServer\Fqn\getReferencedFqn;
 use PhpParser\{NodeVisitorAbstract, Node};
 
 /**
@@ -21,7 +22,7 @@ class ReferencesCollector extends NodeVisitorAbstract
     public function enterNode(Node $node)
     {
         // Check if the node references any global symbol
-        $fqn = $node->getAttribute('ownerDocument')->getReferencedFqn($node);
+        $fqn = getReferencedFqn($node);
         if ($fqn) {
             $this->addReference($fqn, $node);
             // Namespaced constant access and function calls also need to register a reference
diff --git a/src/PhpDocument.php b/src/PhpDocument.php
index 2246a40..0a97ca2 100644
--- a/src/PhpDocument.php
+++ b/src/PhpDocument.php
@@ -16,6 +16,7 @@ use LanguageServer\NodeVisitor\{
 use PhpParser\{Error, Node, NodeTraverser, Parser};
 use PhpParser\NodeVisitor\NameResolver;
 use phpDocumentor\Reflection\DocBlockFactory;
+use function LanguageServer\Fqn\{getDefinedFqn, getVariableDefinition, getReferencedFqn};
 
 class PhpDocument
 {
@@ -297,202 +298,6 @@ class PhpDocument
         return isset($this->definitions[$fqn]);
     }
 
-    /**
-     * Returns the fully qualified name (FQN) that is defined by a node
-     * Examples of FQNs:
-     *  - testFunction()
-     *  - TestNamespace\TestClass
-     *  - TestNamespace\TestClass::TEST_CONSTANT
-     *  - TestNamespace\TestClass::staticTestProperty
-     *  - TestNamespace\TestClass::testProperty
-     *  - TestNamespace\TestClass::staticTestMethod()
-     *  - TestNamespace\TestClass::testMethod()
-     *
-     * @param Node $node
-     * @return string|null
-     */
-    public function getDefinedFqn(Node $node)
-    {
-        // Anonymous classes don't count as a definition
-        if ($node instanceof Node\Stmt\ClassLike && isset($node->name)) {
-            // Class, interface or trait declaration
-            return (string)$node->namespacedName;
-        } else if ($node instanceof Node\Stmt\Function_) {
-            // Function: use functionName() as the name
-            return (string)$node->namespacedName . '()';
-        } else if ($node instanceof Node\Stmt\ClassMethod) {
-            // Class method: use ClassName::methodName() as name
-            $class = $node->getAttribute('parentNode');
-            if (!isset($class->name)) {
-                // Ignore anonymous classes
-                return null;
-            }
-            return (string)$class->namespacedName . '::' . (string)$node->name . '()';
-        } else if ($node instanceof Node\Stmt\PropertyProperty) {
-            // Property: use ClassName::propertyName as name
-            $class = $node->getAttribute('parentNode')->getAttribute('parentNode');
-            if (!isset($class->name)) {
-                // Ignore anonymous classes
-                return null;
-            }
-            return (string)$class->namespacedName . '::' . (string)$node->name;
-        } else if ($node instanceof Node\Const_) {
-            $parent = $node->getAttribute('parentNode');
-            if ($parent instanceof Node\Stmt\Const_) {
-                // Basic constant: use CONSTANT_NAME as name
-                return (string)$node->namespacedName;
-            }
-            if ($parent instanceof Node\Stmt\ClassConst) {
-                // Class constant: use ClassName::CONSTANT_NAME as name
-                $class = $parent->getAttribute('parentNode');
-                if (!isset($class->name) || $class->name instanceof Node\Expr) {
-                    return null;
-                }
-                return (string)$class->namespacedName . '::' . $node->name;
-            }
-        }
-    }
-
-    /**
-     * Returns the FQN that is referenced by a node
-     *
-     * @param Node $node
-     * @return string|null
-     */
-    public function getReferencedFqn(Node $node)
-    {
-        $parent = $node->getAttribute('parentNode');
-
-        if (
-            $node instanceof Node\Name && (
-                $parent instanceof Node\Stmt\ClassLike
-                || $parent instanceof Node\Param
-                || $parent instanceof Node\Stmt\Function_
-                || $parent instanceof Node\Expr\StaticCall
-                || $parent instanceof Node\Expr\ClassConstFetch
-                || $parent instanceof Node\Expr\StaticPropertyFetch
-            )
-        ) {
-            // For extends, implements, type hints and classes of classes of static calls use the name directly
-            $name = (string)$node;
-        // Only the name node should be considered a reference, not the UseUse node itself
-        } else if ($parent instanceof Node\Stmt\UseUse) {
-            $name = (string)$parent->name;
-            $grandParent = $parent->getAttribute('parentNode');
-            if ($grandParent instanceof Node\Stmt\GroupUse) {
-                $name = $grandParent->prefix . '\\' . $name;
-            }
-        // Only the name node should be considered a reference, not the New_ node itself
-        } else if ($parent instanceof Node\Expr\New_) {
-            if (!($parent->class instanceof Node\Name)) {
-                // Cannot get definition of dynamic calls
-                return null;
-            }
-            $name = (string)$parent->class;
-        } else if ($node instanceof Node\Expr\MethodCall || $node instanceof Node\Expr\PropertyFetch) {
-            if ($node->name instanceof Node\Expr || !($node->var instanceof Node\Expr\Variable)) {
-                // Cannot get definition of dynamic calls
-                return null;
-            }
-            // Need to resolve variable to a class
-            if ($node->var->name === 'this') {
-                // $this resolved to the class it is contained in
-                $n = $node;
-                while ($n = $n->getAttribute('parentNode')) {
-                    if ($n instanceof Node\Stmt\Class_) {
-                        if ($n->isAnonymous()) {
-                            return null;
-                        }
-                        $name = (string)$n->namespacedName;
-                        break;
-                    }
-                }
-                if (!isset($name)) {
-                    return null;
-                }
-            } else {
-                // Other variables resolve to their definition
-                $varDef = $this->getVariableDefinition($node->var);
-                if (!isset($varDef)) {
-                    return null;
-                }
-                if ($varDef instanceof Node\Param) {
-                    if (!isset($varDef->type)) {
-                        // Cannot resolve to class without a type hint
-                        // TODO: parse docblock
-                        return null;
-                    }
-                    $name = (string)$varDef->type;
-                } else if ($varDef instanceof Node\Expr\Assign) {
-                    if ($varDef->expr instanceof Node\Expr\New_) {
-                        if (!($varDef->expr->class instanceof Node\Name)) {
-                            // Cannot get definition of dynamic calls
-                            return null;
-                        }
-                        $name = (string)$varDef->expr->class;
-                    } else {
-                        return null;
-                    }
-                } else {
-                    return null;
-                }
-            }
-            $name .= '::' . (string)$node->name;
-        } else if ($parent instanceof Node\Expr\FuncCall) {
-            if ($parent->name instanceof Node\Expr) {
-                return null;
-            }
-            $name = (string)($node->getAttribute('namespacedName') ?? $parent->name);
-        } else if ($parent instanceof Node\Expr\ConstFetch) {
-            $name = (string)($node->getAttribute('namespacedName') ?? $parent->name);
-        } else if (
-            $node instanceof Node\Expr\ClassConstFetch
-            || $node instanceof Node\Expr\StaticPropertyFetch
-            || $node instanceof Node\Expr\StaticCall
-        ) {
-            if ($node->class instanceof Node\Expr || $node->name instanceof Node\Expr) {
-                // Cannot get definition of dynamic names
-                return null;
-            }
-            $className = (string)$node->class;
-            if ($className === 'self' || $className === 'static' || $className === 'parent') {
-                // self and static are resolved to the containing class
-                $n = $node;
-                while ($n = $n->getAttribute('parentNode')) {
-                    if ($n instanceof Node\Stmt\Class_) {
-                        if ($n->isAnonymous()) {
-                            return null;
-                        }
-                        if ($className === 'parent') {
-                            // parent is resolved to the parent class
-                            if (!isset($n->extends)) {
-                                return null;
-                            }
-                            $className = (string)$n->extends;
-                        } else {
-                            $className = (string)$n->namespacedName;
-                        }
-                        break;
-                    }
-                }
-            }
-            $name = (string)$className . '::' . $node->name;
-        } else {
-            return null;
-        }
-        if (
-            $node instanceof Node\Expr\MethodCall
-            || $node instanceof Node\Expr\StaticCall
-            || $parent instanceof Node\Expr\FuncCall
-        ) {
-            $name .= '()';
-        }
-        if (!isset($name)) {
-            return null;
-        }
-        return $name;
-    }
-
     /**
      * Returns the definition node for any node
      * The definition node MAY be in another document, check the ownerDocument attribute
@@ -505,9 +310,9 @@ class PhpDocument
         // Variables always stay in the boundary of the file and need to be searched inside their function scope
         // by traversing the AST
         if ($node instanceof Node\Expr\Variable) {
-            return $this->getVariableDefinition($node);
+            return getVariableDefinition($node);
         }
-        $fqn = $this->getReferencedFqn($node);
+        $fqn = getReferencedFqn($node);
         if (!isset($fqn)) {
             return null;
         }
@@ -558,7 +363,7 @@ class PhpDocument
             return $refCollector->references;
         }
         // Definition with a global FQN
-        $fqn = $this->getDefinedFqn($node);
+        $fqn = getDefinedFqn($node);
         if ($fqn === null) {
             return [];
         }
@@ -574,43 +379,4 @@ class PhpDocument
         }
         return $nodes;
     }
-
-    /**
-     * Returns the assignment or parameter node where a variable was defined
-     *
-     * @param Node\Expr\Variable $n The variable access
-     * @return Node\Expr\Assign|Node\Param|Node\Expr\ClosureUse|null
-     */
-    public function getVariableDefinition(Node\Expr\Variable $var)
-    {
-        $n = $var;
-        // Traverse the AST up
-        do {
-            // If a function is met, check the parameters and use statements
-            if ($n instanceof Node\FunctionLike) {
-                foreach ($n->getParams() as $param) {
-                    if ($param->name === $var->name) {
-                        return $param;
-                    }
-                }
-                // If it is a closure, also check use statements
-                if ($n instanceof Node\Expr\Closure) {
-                    foreach ($n->uses as $use) {
-                        if ($use->var === $var->name) {
-                            return $use;
-                        }
-                    }
-                }
-                break;
-            }
-            // Check each previous sibling node for a variable assignment to that variable
-            while ($n->getAttribute('previousSibling') && $n = $n->getAttribute('previousSibling')) {
-                if ($n instanceof Node\Expr\Assign && $n->var instanceof Node\Expr\Variable && $n->var->name === $var->name) {
-                    return $n;
-                }
-            }
-        } while (isset($n) && $n = $n->getAttribute('parentNode'));
-        // Return null if nothing was found
-        return null;
-    }
 }