Yes it is copy of the standard decision task TS00008276. i have replaced BOR with my custom class so as to enable the binding of _wi_object_id with the class and get the document link in the workitem.
things are working as expected, by copying the standard task i am getting the document link under"object and attachment ' section of workitem. but on clicking of it i am getting the error " user decision ********** has no alternative index 0000.