This work introduces a framework for awareness support in groupware systems, called BW. Awareness gathers the group knowledge, its activities and its overall status. Awareness support is an important feature for groupware systems, since it provides a context for individual contributions, improving these contributions and avoiding contradictory interactions among group members. Despite its importance, awareness support is not systematic and developers must build it from scratch for each new application. The BW framework addresses this issue. It intends to support groupware designers to easily build past event awareness mechanisms. Past event awareness refers to the awareness information about the activities performed in the past, which results may have changed or not be valid anymore. The BW framework has been designed to develop new groupware applications and to improve existing ones. Thus, this framework can be included into asynchronous groupware system that needs a past events awareness support. The BW framework was implemented in Java and tested into the COPSE/CUTE groupware system, validating the statements presented in this work.