This is a customer requirement that just like opening CAD documents from CREO, why can't we open MS documents from windchill and edit within windchill instead of using Windchill Desktop Integration or downloading files and checkin again since a copy will be saved on local drive.
And your question is what?
Desktop Integration is the closest tool available today. You might be able to write a customization to both Windchill and Word to accomplish what you want, but not sure what the justification would be since DI can check documents directly into WC.
Even though their is a local copy of the file, this is no different that the local cache that the CAD workgroup manager use.
WDI is the closest solution as of now I accept but my client was asking a general question like the way we open CAD objects from CREO why can't PTC develop something like when we click on an excel file instead of downloading it another window should open and we should be able to edit excel / docs directly from the window and checkin back to windchill. I explained same thing is happening when we use WDI where in all MS Office products will have integrated tab that allows users to directly checkin to Windchill. Finally they agreed to it.
That wouldn't be like Creo. When you open files in Creo then Windchill is downloading files to a workspace located on your computer (there is also a sync'd version on the server). After you save the files you have to check them in from the workspace. Creo doesn't edit the CAD files directly in Windchill.