WE PRESENT A PATTERN SYSTEM NAMED COCHI (COLLABORATIVE OBJECTS FOR COMMUNICATION AND HUMAN INTERACTION), WHICH SUPPORTS REUSABILITY IN THE DEVELOPMENT OF GROUPWARE AT THREE LEVELS OF ABSTRACTION: ARCHITECTURE, DESIGN AND IMPLEMENTATION. COCHI.~AS TWO PROPERTIES: EASE OFUSE ANDJLEXIBILITY, BUT IN CONTRAST WITH OTHER TOOLS, COCHI MAINTAINS AN EQUILIBRIUM BETWEEN BOTH GOALS PROVIDING A CLASS FRAMEWORK THAT ALLOWS A DEVELOPER TO IMPLEMENT GROUPWARE APPLICATIONS REDUCING THE IMPLEMENTATION EFFORT AND A SET OF ARCHITECTURAL AND DESIGN PATTERNS THAT ADDS JLEXIBILITY TO THE PLATFORM AND PERMITS ITS EXTENSION WITH NEW FEATURES. THIS MAKES COCHI PARTICULARLY USEFUL FOR THE RESEARCH OF NEW MULTI-USER INTERFACE WIDGETS, COORDINATION MECHANISMS, JLOOR CONTROL POLICIES, ETC. WE SHOW HOW COCHI'S CLASSFRAMEWORK REDUCES THE EFFORT REQUIRED TO IMPLEMENT SYNCHRONOUS GROUPWARE AND HOW THE ARCHITECTURAL AND DESIGN PATTERNS HAVE BEEN EXTENDED TO SUPPORTFEATURES LIKE QUALITY OFSERVICE (QOS) AND EMOTIONAL AWARENESS NOT PRESENT ORIGINALLY. THUS, WE SHOW HOW EASE OF IMPLEMENTATION IS NOT NECESSARILY IN OPPOSITION WITH EXTENSIBILITY IN REUSABLE SOFTWARE.WE PRESENT A PATTERN SYSTEM NAMED COCHI (COLLABORATIVE OBJECTS FOR COMMUNICATION AND HUMAN INTERACTION), WHICH SUPPORTS REUSABILITY IN THE DEVELOPMENT OF GROUPWARE AT THREE LEVELS OF ABSTRACTION: ARCHITECTURE, DESIGN AND IMPLEMENTATION. COCHI.~AS TWO PROPERTIES: EASE OFUSE ANDJLEXIBILITY, BUT IN CONTRAST WITH OTHER TOOLS, COCHI MAINTAINS AN EQUILIBRIUM BETWEEN BOTH GOALS PROVIDING A CLASS FRAMEWORK THAT ALLOWS A DEVELOPER TO IMPLEMENT GROUPWARE APPLICATIONS REDUCING THE IMPLEMENTATION EFFORT AND A SET OF ARCHITECTURAL AND DESIGN PATTERNS THAT ADDS JLEXIBILITY TO THE PLATFORM AND PERMITS ITS EXTENSION WITH NEW FEATURES. THIS MAKES COCHI PARTICULARLY USEFUL FOR THE RESEARCH OF NEW MULTI-USER INTERFACE WIDGETS, COORDINATION MECHANISMS, JLOOR CONTROL POLICIES, ETC. WE SHOW HOW COCHI´S CLASSFRAMEWORK REDUCES THE EFFORT REQUIRED TO IMPLEMENT SYNCHRONOUS GROUPWARE AND HOW THE ARCHITECTURAL AND DESIGN PATTERNS HAVE BEEN EXTENDED TO SUPPORTFEATURES LIKE QUALITY OFSERVICE (QOS) AND EMOTIONAL AWARENESS NOT PRESENT ORIGINALLY. THUS, WE SHOW HOW EASE OF IMPLEMENTATION IS NOT NECESSARILY IN OPPOSITION WITH EXTENSIBILITY IN REUSABLE SOFTWARE.