To solve a problem of a conventional system that a user only can carry out document edition on data different from display data observed previously if the other user edits and changes the document when switching a reference mode to an edition mode is instructed for edition work on a client side in a document management database having the display data in addition to actual data.

In the document management database having the actual data and the display data, the actual data of a document are stored as temporary data at opening in a reference mode. In change operation from the reference mode to the edition mode, when the change of a document is confirmed by change detection before transfer to edition action, editing action can be carried out not on the changed document data but on the displayed document data using the temporary data stored at opening in the reference mode.