A.1 A number of environment variables can be used to ease the setting up of a collaborative session.

  • COVISA_CENTRAL_PORT – this should be set to the port number that the COVISA Server is using. Some port numbers are reserved and are not available at the user level, the port number that we typically use is 5127; this default value is set when IRIS Explorer is installed.

  • COVISA_CENTRAL_MACHINE – this should be set to the machine name where the COVISA Server is running. It should be set in the form: csindy12.leeds.ac.uk

  • USER – this sets the UserName widget on the MServer module and contains the name used to identify a collaborator in the session. It is often set by default by UNIX command shells. If this is not the case then this variable may be explicitly set by the user using the appropriate command for their chosen shell. For the csh and tcsh shells this would be

    setenv USER <username>

    before starting up IRIS Explorer.

The MServer module picks up this information and uses it as default values for some of its widgets. These can be altered at run time using the module control panel. These values are particularly useful when creating collaborative applications, or if the COVISA Server is always run at a default location. The COVISA Server, by default, uses the COVISA_CENTRAL_PORT variable to set its port number. This can be changed by using the

-port <portnumber>

command line argument when running the COVISA Server from a command shell. See Section 2.1 for more details.

A.2 The COVISA system, like the rest of IRIS Explorer, is completely heterogenous. This means that sessions can be conducted not only between users on different versions of UNIX, but also between users on UNIX and Windows platforms.


A.3 When a module is duplicated (using the duplicate option from the popup menu on the module), the effect varies depending on the current state of the module. If it had not been initiated into the collaborative session (by pressing the Initiate button) then the duplicated module automatically joins the collaborative session and forms a new group. If it had been initiated and was already a group member, then the duplicate appears to be a second member of the same group. The COVISA Server will not allow more than a single member of a group by one collaborator, and will eventually kill the duplicated module (usually when it attempts to become connected for the first time).

A.4 When you replace a collaborative module (using the replace option from the popup menu on the module), it deletes the old module and starts a new one. When this module is enabled it initiates itself into the collaborative session and starts a new group (i.e., it will have a different Group Number and hence belong to a different group). This happens irrespective of whether the module had previously been initiated or not. See Section 4.3 for a detailed description of starting up a collaborative module.

A.5 The MSharePointer module's Output port should be wired to the Render module's Input port, and the Render module's Pick port should be wired to port Input of MSharePointer. The Render module then needs to be set into the appropriate mode, see Section


A.6 Although both parties have successfully connected to a COVISA Server, it sounds like you have connected to different servers. For data to be passed between collaborators, they all have to be connected to a single COVISA Server. See Section 4.1 for a detailed description of how to start up a collaborative session.

A.7 For a collaborative session to work correctly, the COVISA module suite must be installed on all collaborators' machines, with the modules appearing in the Librarian of each collaborator. Also, any other user written modules that need to be used within the session should be installed locally for each collaborator. The system is not currently capable of downloading module code at run time.

A.8 The COVISA Server can be run in one of two different modes:

  • Store and Foreward (default mode) – in this mode the server keeps a copy of the last shared data object passed to it for each collaborative group. When a collaborator joins late, a copy of any stored data is automatically passed on.

  • Pass – in this mode the server merely passes data to collaborators who are currently members of the session. No data is stored at the server.

For a more detailed description see Section 4.1.