1. A method executed on a computing device for merging sequences of ordered objects, the method comprising: determining common and non-common objects from a collaboratively authored document among a base and two derived sequences, wherein the base sequence is an original sequence of the ordered objects from a master version of the collaboratively authored document and the two sequences are derived from the original sequence based on addition, removal, and reorder of the objects to a modified version of the collaboratively authored document; merging a z-position of the common and non-common objects in relation to each other according to a z-order on z-axis, by: determining a final sequence of the common objects on the z-axis, wherein objects along the z-axis include one or more of: overlapping objects, embedded objects and overlaid graphics; and determining a final sequence of all objects based on positioning the non-common objects relative to the common objects in their respective sequences on the z-axis, wherein the final sequence represents changes made by two or more users to the base sequence of the collaboratively authored document including rearranged objects, new objects, and removed objects across the z-axis.