diff --git a/Sources/HTMLKitDOMExceptions.m b/Sources/HTMLKitDOMExceptions.m
index 7a0d349..1a596a3 100644
--- a/Sources/HTMLKitDOMExceptions.m
+++ b/Sources/HTMLKitDOMExceptions.m
@@ -14,3 +14,5 @@ NSString * const HTMLKitNotFoundError = @"NotFoundError";
 NSString * const HTMLKitNotSupportedError = @"NotSupportedError";
 NSString * const HTMLKitSyntaxError = @"SyntaxError";
 NSString * const HTMLKitInvalidCharacterError = @"InvalidCharacterError";
+NSString * const HTMLKitInvalidNodeTypeError = @"InvalidNodeTypeError";
+NSString * const HTMLKitIndexSizeError = @"IndexSizeError";
diff --git a/Sources/HTMLRange.h b/Sources/HTMLRange.h
index 1a15245..860a54d 100644
--- a/Sources/HTMLRange.h
+++ b/Sources/HTMLRange.h
@@ -67,7 +67,7 @@
  @param startNode The new node of the start boundary.
  @param startOffset The new offset of the start boundary.
  */
-- (void)setStartNode:(HTMLNode *)startNode startOffset:(NSUInteger)startOffset;
+- (void)setStartNode:(HTMLNode *)node startOffset:(NSUInteger)offset;
 
 /**
  Sets the end boundary.
@@ -75,7 +75,7 @@
  @param startNode The new node of the end boundary.
  @param startOffset The new offset of the end boundary.
  */
-- (void)setEndNode:(HTMLNode *)endNode endOffset:(NSUInteger)endOffset;
+- (void)setEndNode:(HTMLNode *)node endOffset:(NSUInteger)offset;
 
 /**
  Sets the start boundary before the given node.
diff --git a/Sources/HTMLRange.m b/Sources/HTMLRange.m
index f403df6..e7f2550 100644
--- a/Sources/HTMLRange.m
+++ b/Sources/HTMLRange.m
@@ -7,7 +7,90 @@
 //
 
 #import "HTMLRange.h"
+#import "HTMLKitDOMExceptions.h"
 
 @implementation HTMLRange
 
+
+#pragma mark - Boundaries
+
+NS_INLINE void CheckValidBoundaryNode(HTMLNode *node, NSString *cmd)
+{
+	if (node == nil || node.nodeType == HTMLNodeDocumentType) {
+		[NSException raise:HTMLKitNotFoundError
+					format:@"%@: Invalid Node Type Error, %@ is not a valid range boundary node.",
+		 cmd, node];
+	}
+}
+
+NS_INLINE void CheckValidBoundaryOffset(HTMLNode *node, NSUInteger offset, NSString *cmd)
+{
+	if (node == nil || node.nodeType == HTMLNodeDocumentType) {
+		[NSException raise:HTMLKitIndexSizeError
+					format:@"%@: Index Size Error, invalid index %lu for range boundary node %@.",
+		 cmd, (unsigned long)offset, node];
+	}
+}
+
+NS_INLINE NSComparisonResult CompareBoundaries(HTMLNode *startNode, NSUInteger startOffset, HTMLNode *endNode, NSUInteger endOffset)
+{
+	if (startNode == endNode) {
+		if (startOffset == endOffset) {
+			return NSOrderedSame;
+		} else if (startOffset < endOffset) {
+			return NSOrderedAscending;
+		} else {
+			return NSOrderedDescending;
+		}
+	}
+
+	HTMLDocumentPosition position = [startNode compareDocumentPositionWithNode:endNode];
+	if ((position & HTMLDocumentPositionFollowing) == HTMLDocumentPositionFollowing) {
+			// Check Spec
+	}
+
+	if ([startNode containsNode:endNode]) {
+		HTMLNode *child = endNode;
+		while (child.parentNode != startNode) {
+			child = child.parentNode;
+		}
+		if ([child.parentNode indexOfChildNode:child] > startOffset) {
+			return NSOrderedDescending;
+		}
+	}
+
+	return NSOrderedAscending;
+}
+
+- (void)setStartNode:(HTMLNode *)node startOffset:(NSUInteger)offset
+{
+	CheckValidBoundaryNode(node, NSStringFromSelector(_cmd));
+
+	CheckValidBoundaryOffset(node, offset, NSStringFromSelector(_cmd));
+
+	if (self.rootNode != node.rootNode ||
+		CompareBoundaries(node, offset, _endContainer, _endOffset) == NSOrderedDescending) {
+		_endContainer = node;
+		_endOffset = offset;
+	}
+
+	_startContainer = node;
+	_startOffset = offset;
+}
+
+- (void)setEndNode:(HTMLNode *)node endOffset:(NSUInteger)offset
+{
+	CheckValidBoundaryNode(node, NSStringFromSelector(_cmd));
+
+	CheckValidBoundaryOffset(node, offset, NSStringFromSelector(_cmd));
+
+	if (self.rootNode != node.rootNode ||
+		CompareBoundaries(node, offset, _startContainer, _startOffset) == NSOrderedAscending) {
+		_startContainer = node;
+		_startOffset = offset;
+	}
+
+	_endContainer = node;
+	_endOffset = offset;
+}
 @end
diff --git a/Sources/include/HTMLKitDOMExceptions.h b/Sources/include/HTMLKitDOMExceptions.h
index 115b884..f11518c 100644
--- a/Sources/include/HTMLKitDOMExceptions.h
+++ b/Sources/include/HTMLKitDOMExceptions.h
@@ -14,3 +14,6 @@ extern NSString * const HTMLKitNotSupportedError;
 
 extern NSString * const HTMLKitSyntaxError;
 extern NSString * const HTMLKitInvalidCharacterError;
+
+extern NSString * const HTMLKitInvalidNodeTypeError;
+extern NSString * const HTMLKitIndexSizeError;