Systems

Several important systems, both applications and infrastructures, have been developed to support collaboration. The applications include:

• RTCAL (Real-Time Calendaring System) []: Developed as part of a Ph.D. thesis at MIT, it allows multiple users to schedule meetings in real-time. This research was instrumental in identifying several of the systems issues in collaborative systems.

• Cognoter [,,]: Developed as part of the Xerox suite of collaborative applications, Cognoter allows users to collaboratively design an outline. A unique feature of this system is an automatically enforced meeting process. This research also helped identify issues in coupling among users, experimenting both with WYSIWIS (What You See Is What I See) and non WYSIWIS user interfaces.

• Grove [,]: Grove is also a group outline editor, developed at MCC. It recognizes the structure of the outline and provides fine-grained access control and non WYSIWIS user interface.

• GroupDraw []: GroupDraw is a group drawing tool, developed at the University of Calgary, which provides a new form of concurrency control called optimistic locking.

• MUD (MultiUser Dungeons) []: Developed by researchers at Xerox and elsewhere, it provides a text-based virtual environment in which people can meet and interact with each other based on which rooms they have entered.

• DIVE (Distributed Interactive Virtual Environment)/MASSIVE: Developed about the same time at Amsterdam and University of Nottingham, these systems, like MUDs, provide virtual meeting environments except that these environments are based on 3-D graphics.

• Coordinator []: Developed at Stanford, it is based on a theory of collaboration called the ''speech-act'' theory and can be considered one of the first workflow systems.

• ActionWorkflow []: Developed by the inventors of Coordinator, this system is an extension of the Coordinator that provides more extensive workflow support.

• Quilt []: Developed at Bellcore, it provides rich support for collaborative writing, including logging of concrete and abstract user actions, typed annotations, and role-based access control.

• PREP (work in PREParation editor) [,]: Also supporting collaborative writing, PREP has been developed at CMU and provides novel facilities for commenting on the document, pinpointing the differences between different versions of the document, and coupling among users.

• CSI (Collaboration Software Inspection) []: This system supports both synchronous and asynchronous inspection of documents, providing facilities for making transitions between these phases of group work.

The infrastructures include:

• Web/Java: They offer several general-purpose facilities for constructing collaborative applications.

• XTV []: An example of a centralized shared window system, developed at ODU and UNC, XTV allows the windows created by an existing, collaboration-unaware, X application to be shared among multiple isers. It creates a single copy of the X application for all users sharing the application.

• MMConf []: An example of replicated shared window system, developed at BBN, this system supports sharing of collaboration-aware applications and creates a replica of the shared application for each user sharing the application.

• GroupKit []: Unlike the previous two infrastructures, which are extensions of window systems, GroupKit is an extension of a user-interface toolkit. Like MMConf, it supports replicated, collaboration-aware, applications, but provides higher-level support for implementing the application. Two different versions of it have been implemented, extending the InterViews and TCL/TK toolkits, respectively.

• Colab Programming Environment []: Also developed as part of the Xerox Colab system, this environment extends an object-oriented programming language with constructs for sharing arbitrary objects among users.

• Rendezvous []: Developed at Bellcore, it provides a declarative, object-oriented, constraint-based system for defining WYSIWIS and non-WYSIWIS user interfaces to shared objects.

• DistView []: Developed at the University of Michigan, it provides fine-grained replication of shared objects.

• Coterie []: Another distributed shared-object system, it has been developed at Columbia University and used to develop collaborative virtual environments.

• Suite []: Suite has been developed at Purdue and UNC and extends the C/Unix/X environment with support for a rich set of collaboration functions, including coupling, multiuser undo, merging, access control and concurrency control. It provides flexible support for each function, supporting high-level parameters defining a rich design space for the function.

• Oz []: This is a web-based system for defining process control.

• Trellis []: Developed at University of Maryland, Trellis associates shared objects with processes that control access to the document, thereby intergrating data and control.

• Sui'tre []: An example of interoperating systems, Sui'tre (pronounced Sweeter) is an integration of Suite and Trellis, combining properties of both systems and thereby providing both an interpretive and compiled environment for defining collaboration functions.

• Message Bus []: Developed at Brown University as part of the Field software development environment, it is a system supporting interoperation among general software system such as debuggers and editors.

• DistEdit []: Developed at the University of Michigan, it can be considered a special case of the message bus that connects existing single-user editors of different users to each other, thereby offering collaborative editing.