Omeka 2.0 is the second major release. It represents many fundamental changes and improvements to the core and development API Core Changes Fixed numerous issues Shifted naming conventions for better comformity to upcoming Zend 2.0 standards Removed Data Types from ElementTexts Removed Entities to represent Users. All user information is now directly on User objects Added Dublin Core information to Collections Removed Orderable mixin Added Searchable mixin Ownable mixin now named Mixin_Owner Taggable mixin now named Mixin_Tag ActsAsElementText mixin now named Mixin_ElementText PublicFeatures mixin now named Mixin_PublicFeatured Omeka_Acl removed. User Zend_Acl instead Derivative images now produced for many more file types archive directory changed to files archive/files directory changed to files/original Phased loading is now removed in favor of loading resources when needed API Changes Removed many functions with overlapping or similar functionality details Functions no long echo directly and instead return values Form functions have been removed in favor of using Zend Form Helpers Many new and renamed hooks and filters details Arguments passed to all hooks consolidated into one $args array beforeSaveForm() and afterSaveForm() callbacks removed from records Omeka_Form_Admin class added to help build simple admin forms Omeka_Plugin class renamed Omeka_Plugin_AbstractPlugin Controllers should now extend Omeka_Controller_AbstractActionController Models should now extend Omeka_Record_AbstractRecord Db wrappers removed :getDb, getTable, and findById are replaced by equivalent calls to _helper->db->{methodName}. Omeka_Context removed in favor of using Zend_Registry Plugins can now add their content to search with Mixin_Search Additional details can be found in the codex and in the new documentation