uDig is an open source desktop application framework, built with Eclipse Rich Client (RCP) technology. uDig can be used as a stand-alone application. The goal of uDig is to provide a complete Java solution for desktop GIS data access, editing, and viewing. uDig can be extended with RCP "plug-ins" and it can be used as a plug-in in an existing RCP application. uDig features coordinate reference system support for all data sources, and on-the-fly coordinate system transformation and full support for network-based installation of optional features and upgrading of existing features.