     var dirty: Bool {get set}
 }
 
-public class GraphContext {
+open class GraphContext {
     
     // Singletons
     //static let sharedInstance 
     
-    public let url: NSURL
-    public let docURL: NSURL
+    open let url: URL
+    open let docURL: URL
     //public var error: NSError?  // readonly?
     var temporary = false  // // delete data wrapper after closing the context
     

        return result;
    }
    
    public func update(inout aNode: Node) {
        if aNode.dirty {
            nodeStore.updateValue(aNode)
            

        return result;
    }
    
    func update(_ aProperty: inout Property) {
        if aProperty.dirty {
            propertyStore.updateValue(aProperty)
            
