@@ -14,10 +14,12 @@
  * file.
  */
 
 #import "OFXMLNode.h"
 
+OF_ASSUME_NONNULL_BEGIN
+
 @class OFString;
 @class OFMutableString;
 #ifndef DOXYGEN
 @class OFArray OF_GENERIC(ObjectType);
 @class OFMutableArray OF_GENERIC(ObjectType);
@@ -39,17 +41,19 @@
 }
 
 #ifdef OF_HAVE_PROPERTIES
 @property (copy) OFString *name;
 # ifdef __cplusplus
-@property (copy, getter=namespace, setter=setNamespace:) OFString *namespace_;
+@property (copy, getter=namespace, setter=setNamespace:, nullable)
+    OFString *namespace_;
 # else
-@property (copy) OFString *namespace;
+@property (copy, nullable) OFString *namespace;
 # endif
-@property (copy) OFString *defaultNamespace;
-@property (readonly, copy) OFArray OF_GENERIC(OFXMLAttribute*) *attributes;
-@property (copy) OFArray OF_GENERIC(OFXMLNode*) *children;
+@property (copy, nullable) OFString *defaultNamespace;
+@property (copy, readonly, nullable) OFArray OF_GENERIC(OFXMLAttribute*)
+    *attributes;
+@property (copy, nullable) OFArray OF_GENERIC(OFXMLNode*) *children;
 #endif
 
 /*!
  * @brief Creates a new XML element with the specified name.
  *
@@ -65,11 +69,11 @@
  * @param stringValue The value for the element
  * @return A new autoreleased OFXMLElement with the specified element name and
  *	   value
  */
 + (instancetype)elementWithName: (OFString*)name
-		    stringValue: (OFString*)stringValue;
+		    stringValue: (nullable OFString*)stringValue;
 
 /*!
  * @brief Creates a new XML element with the specified name and namespace.
  *
  * @param name The name for the element
@@ -76,11 +80,11 @@
  * @param namespace_ The namespace for the element
  * @return A new autoreleased OFXMLElement with the specified element name and
  *	   namespace
  */
 + (instancetype)elementWithName: (OFString*)name
-		      namespace: (OFString*)namespace_;
+		      namespace: (nullable OFString*)namespace_;
 
 /*!
  * @brief Creates a new XML element with the specified name, namespace and
  * 	  string value.
  *
@@ -89,12 +93,12 @@
  * @param stringValue The value for the element
  * @return A new autoreleased OFXMLElement with the specified element name,
  *	   namespace and value
  */
 + (instancetype)elementWithName: (OFString*)name
-		      namespace: (OFString*)namespace_
-		    stringValue: (OFString*)stringValue;
+		      namespace: (nullable OFString*)namespace_
+		    stringValue: (nullable OFString*)stringValue;
 
 /*!
  * @brief Creates a new element with the specified element.
  *
  * @param element An OFXMLElement to initialize the OFXMLElement with
@@ -138,11 +142,11 @@
  * @param stringValue The value for the element
  * @return An initialized OFXMLElement with the specified element name and
  *	   value
  */
 - initWithName: (OFString*)name
-   stringValue: (OFString*)stringValue;
+   stringValue: (nullable OFString*)stringValue;
 
 /*!
  * @brief Initializes an already allocated OFXMLElement with the specified name
  *	  and namespace.
  *
@@ -150,11 +154,11 @@
  * @param namespace_ The namespace for the element
  * @return An initialized OFXMLElement with the specified element name and
  *	   namespace
  */
 - initWithName: (OFString*)name
-     namespace: (OFString*)namespace_;
+     namespace: (nullable OFString*)namespace_;
 
 /*!
  * @brief Initializes an already allocated OFXMLElement with the specified name,
  *	  namespace and value.
  *
@@ -163,12 +167,12 @@
  * @param stringValue The value for the element
  * @return An initialized OFXMLElement with the specified element name,
  *	   namespace and value
  */
 - initWithName: (OFString*)name
-     namespace: (OFString*)namespace_
-   stringValue: (OFString*)stringValue;
+     namespace: (nullable OFString*)namespace_
+   stringValue: (nullable OFString*)stringValue;
 
 /*!
  * @brief Initializes an already allocated OFXMLElement with the specified
  *	  element.
  *
@@ -215,39 +219,51 @@
 /*!
  * @brief Sets the namespace of the element.
  *
  * @param namespace_ The new namespace
  */
-- (void)setNamespace: (OFString*)namespace_;
+- (void)setNamespace: (nullable OFString*)namespace_;
 
 /*!
  * @brief Returns the namespace of the element.
  *
  * @return The namespace of the element
  */
-- (OFString*)namespace;
+- (nullable OFString*)namespace;
+
+/*!
+ * @brief Sets a prefix for a namespace.
+ *
+ * @param prefix The prefix for the namespace
+ * @param namespace_ The namespace for which the prefix is set
+ */
+- (void)setPrefix: (OFString*)prefix
+     forNamespace: (OFString*)namespace_;
+
+/*!
+ * @brief Binds a prefix for a namespace.
+ *
+ * @param prefix The prefix for the namespace
+ * @param namespace_ The namespace for which the prefix is bound
+ */
+- (void)bindPrefix: (OFString*)prefix
+      forNamespace: (OFString*)namespace_;
+
+/*!
+ * @brief Sets the default namespace for the element to be used if there is no
+ *	  parent.
+ *
+ * @param defaultNamespace The default namespace for the element
+ */
+- (void)setDefaultNamespace: (nullable OFString*)defaultNamespace;
 
 /*!
  * @brief Returns an OFArray with the attributes of the element.
  *
  * @return An OFArray with the attributes of the element
  */
-- (OFArray OF_GENERIC(OFXMLAttribute*)*)attributes;
-
-/*!
- * @brief Removes all children and adds the children from the specified array.
- *
- * @param children The new children to add
- */
-- (void)setChildren: (OFArray OF_GENERIC(OFXMLNode*)*)children;
-
-/*!
- * @brief Returns an array of OFXMLNodes with all children of the element.
- *
- * @return An array of OFXMLNodes with all children of the element
- */
-- (OFArray OF_GENERIC(OFXMLNode*)*)children;
+- (nullable OFArray OF_GENERIC(OFXMLAttribute*)*)attributes;
 
 /*!
  * @brief Adds the specified attribute.
  *
  * If an attribute with the same name and namespace already exists, it is not
@@ -279,11 +295,11 @@
  * @param name The name of the attribute
  * @param namespace_ The namespace of the attribute
  * @param stringValue The value of the attribute
  */
 - (void)addAttributeWithName: (OFString*)name
-		   namespace: (OFString*)namespace_
+		   namespace: (nullable OFString*)namespace_
 		 stringValue: (OFString*)stringValue;
 
 /*!
  * @brief Returns the attribute with the specified name.
  *
@@ -298,11 +314,11 @@
  * @param attributeName The name of the attribute
  * @param attributeNS The namespace of the attribute
  * @return The attribute with the specified name and namespace
  */
 - (OFXMLAttribute*)attributeForName: (OFString*)attributeName
-			  namespace: (OFString*)attributeNS;
+			  namespace: (nullable OFString*)attributeNS;
 
 /*!
  * @brief Removes the attribute with the specified name.
  *
  * @param attributeName The name of the attribute
@@ -314,37 +330,25 @@
  *
  * @param attributeName The name of the attribute
  * @param attributeNS The namespace of the attribute
  */
 - (void)removeAttributeForName: (OFString*)attributeName
-		     namespace: (OFString*)attributeNS;
-
-/*!
- * @brief Sets a prefix for a namespace.
- *
- * @param prefix The prefix for the namespace
- * @param namespace_ The namespace for which the prefix is set
- */
-- (void)setPrefix: (OFString*)prefix
-     forNamespace: (OFString*)namespace_;
-
-/*!
- * @brief Binds a prefix for a namespace.
- *
- * @param prefix The prefix for the namespace
- * @param namespace_ The namespace for which the prefix is bound
- */
-- (void)bindPrefix: (OFString*)prefix
-      forNamespace: (OFString*)namespace_;
-
-/*!
- * @brief Sets the default namespace for the element to be used if there is no
- *	  parent.
- *
- * @param defaultNamespace The default namespace for the element
- */
-- (void)setDefaultNamespace: (OFString*)defaultNamespace;
+		     namespace: (nullable OFString*)attributeNS;
+
+/*!
+ * @brief Removes all children and adds the children from the specified array.
+ *
+ * @param children The new children to add
+ */
+- (void)setChildren: (nullable OFArray OF_GENERIC(OFXMLNode*)*)children;
+
+/*!
+ * @brief Returns an array of OFXMLNodes with all children of the element.
+ *
+ * @return An array of OFXMLNodes with all children of the element
+ */
+- (nullable OFArray OF_GENERIC(OFXMLNode*)*)children;
 
 /*!
  * @brief Adds a child to the OFXMLElement.
  *
  * @param child An OFXMLNode which is added as a child
@@ -413,11 +417,11 @@
  * @brief Returns all children that have the specified namespace.
  *
  * @return All children that have the specified namespace
  */
 - (OFArray OF_GENERIC(OFXMLElement*)*)elementsForNamespace:
-    (OFString*)elementNS;
+    (nullable OFString*)elementNS;
 
 /*!
  * @brief Returns the first child element with the specified name.
  *
  * @param elementName The name of the element
@@ -439,19 +443,22 @@
  * @param elementName The name of the element
  * @param elementNS The namespace of the element
  * @return The first child element with the specified name and namespace
  */
 - (OFXMLElement*)elementForName: (OFString*)elementName
-		      namespace: (OFString*)elementNS;
+		      namespace: (nullable OFString*)elementNS;
 
 /*!
  * @brief Returns the child elements with the specified name and namespace.
  *
  * @param elementName The name of the elements
  * @param elementNS The namespace of the elements
  * @return The child elements with the specified name and namespace
  */
-- (OFArray OF_GENERIC(OFXMLElement*)*)elementsForName: (OFString*)elementName
-					    namespace: (OFString*)elementNS;
+- (OFArray OF_GENERIC(OFXMLElement*)*)
+    elementsForName: (OFString*)elementName
+	  namespace: (nullable OFString*)elementNS;
 @end
+
+OF_ASSUME_NONNULL_END
 
 #import "OFXMLElement+Serialization.h"