The main issue in designing the structure for CSCW systems is to provide efficientcollaboration mechanisms. We propose here a hierarchical collaboration mechanism scheme whichconsists of three levels:system-oriented

application-oriented and operation object-oriented collaboration support. In accordance to this hierarchical collaboration mechanism

we explore a platformbased architecture of CSCW systems that can accommodate multiple cooperative applications. Withproviding all of the three-layer cooperation mechanis ms

multimedia desktop conferencing systemTH-MDCS can support geographically separative group members which are of different fields

seated at their desks

cooperating at the same time or at different time by means of sharing information in such multimdia forms as video

audio

image

graphics and text to carry out various taskstogether.