The Open Document statement for Explorer BOXI 3.1 (former polestar) is:
You can find the documentid via Query Builder (as this is not sown in InfoView) and the CUID (which is in the properties of the space located in InfoView).
Open Query Builder: http://servername:port/AdminTools/
then run the SQL query: SELECT SI_CONTENT_ID FROM CI_INFOOBJECTS WHERE SI_CUID=’CUID_FOUND_IN_INFOVIEW‘
BTW: I came across this video that explains it better.