This paper describes the Virtual Workspace System (VWS) which provides a service for sharing state (both data and meta-data or schema) for asynchronous collaborating engineering applications. Key features are:(1) a reliable and platform independent message transport mechanism between client workspaces; (2) an ontological formalism for describing the content of collaborating workspaces, based on the object-oriented model and extending it with notion of constraints; (3) selective sharing based on interest; (4) ability to group events together into transactions; (5) support for conflict detectionhesolution support; and, (6) collaboration policies that can be set at the object level (e.g., a user can be notified of changes to object of class C1 immediately, but not so for objects of class C2). The VWS system is being used to develop a collaborative application to support both design of facilities and maintenance management at the U.S. Army's Fort Gordon.