Update package for offline synchronization of software updates

A software update package for use by an update agent executing on a client computer for updating a software application in an offline manner, the software update package comprising:

• an update catalog file, wherein the update catalog file is an XML file formatted according to a predetermined schema, and includes:
• a list of updates available in the update package;
• and
• a table of file locations of files corresponding to each update available in the update package;
• a plurality of update fragments, such that for each update available in the update package a corresponding set of update fragments is included in the update package.

A software update system implementable on a client computer for updating a software application on the client computer from an update package located on computer-readable media, the software update system comprising:

• an update agent that updates the software application on the client computer according to software update data from an update source, the update agent including:
• a communication module configured to obtain software update data from the update source over a communication network, and also from a media module;
• and
• a media module configured to obtain software update data stored on computer-readable media, wherein the media module is further configured to implement the same communication interfaces as the update source when the communication module communicates with the update source over the communication network;
• wherein the communication module is further configured to communicate with the media module in the same manner as it would communicate with the update source.