Before CRM 2015 Update 1 release, specialized messages were required to update certain entity attribute values. These were AssignRequest to change owner of a record, SetStateRequest to change status of a record, SetParentSystemUserRequest, etc. In this release, UpdateRequest can now be used to set these attributes.
Thus with Update 1 release following specialized message will be deprecated.
These specialized messages will continue to work with the 2011 endpoint. However, the recommendation is to use the UpdateRequest or Update method when possible to set these attributes. The Update message simplifies the SDK API and makes it easier to code standard data integration tools used with Dynamics CRM. In addition, it is easier to code and register a plug-in to execute for a single Update message instead of multiple specialized messages. The AttributeMetadata.IsValidForUpdate property for the above listed attributes has been changed to true in this release to enable this capability.
For plug-ins, when update requests are processed that include both owner fields plus other standard fields for business owned entities, plug-ins registered for the Update message in pipeline stage 20 and/or stage 40 execute once for all non-owner fields, and then once for the owner fields.
For workflows, when update requests are processed that include both owner fields plus other standard fields, workflows registered for the Update message execute once for all non-owner fields, and then once for the owner fields. Workflows registered for the Assign message by users continue to be triggered by updates to owner fields. When update requests are processed that include both state/status fields plus other standard fields, workflows registered for the Update message execute once for all non-state/status fields, and then once for the state/status fields. Workflows registered for the Change Status step continue to be triggered by updates to state/status fields.