Converting a graphic object from a first format to a second format with the aid of a stored checksum

A computer program product, encoded on a computer-readable medium, operable to cause data processing apparatus to perform operations comprising:

• obtaining an electronic document in a first format, the electronic document comprising a graphic object represented using a main dataset and a private dataset;
• normalizing the main dataset of the graphic object of the electronic document stored in an object model in memory;
• computing a checksum for the normalized main dataset of the graphic object;
• comparing the computed checksum with a stored checksum located in the private dataset of the electronic document;
• and
• converting the electronic document from the first format to a second format based in part on a result of the comparing, wherein the converting comprises, when the computed checksum and the stored checksum do not match, propagating a change from the main dataset to the private dataset.

A system comprising:

• a user interface device;
• and
• one or more computers operable to interact with the user interface device and to:
• obtain an electronic document in a first format, the electronic document comprising a graphic object represented using a main dataset and a private dataset;
• normalize the main dataset of the graphic object of the electronic document stored in an object model in memory;
• compute a checksum for the normalized main dataset of the graphic object;
• compare the computed checksum with a stored checksum located in the private dataset of the electronic document;
• and
• convert the electronic document from the first format to a second format based in part on a result of the comparing, wherein the converting comprises, when the computed checksum and the stored checksum do not match, propagating a change from the main dataset to the private dataset.