The user may run a variety of applications. For example, the user usually runs a Conference Manager application, that lets the user control and know what is going on in a conference. A user can also run two other distinguishable types of application, called <#1797#> conference aware<#1797#> and <#1798#> conference transparent<#1798#>. Conference aware applications have been explicitly implemented as conferencing applications for the CAR system, such as a purpose-written shared editor. Conference transparent applications are ones that have been implemented either as stand-alone, or else as distributed, but unaware of possible interactions with other distributed applications. In both these cases, a so-called <#1799#> Nest<#1799#> program is used to encapsulate the application and map Car Conference Library calls and Notifications into meaningful application specific actions. A Nest program must be written for each new type of conference transparent application to implement these mappings. Examples of Conference Transparent Applications currently fall into 3 types:
  1. X Windows based applications These are conferenced by using a CAR version of Shared X, and a Nest for Shared X to provide Application Inclusion/Termination or Exclusion, Floor Control and other CAR functions[#CAR##1#]. Shared X is a mechanism for replicating the window of an X Windows client program on a number of servers' displays. The modfel is illustrated in the diagram#fnshx#1802>.

    Figure: Shared X Windows

    Other shared window paradigms are feasible, as long as they allow single user applications to produce replicated bitmap display output, and have modest control mechanisms for the workstation providing input at any one time.

  2. Conventional Interactive Applications. These include applications that are normally run on a workstation interactively by a single user. For instance, editors (whether text or graphics) fall into this category. Each of these requires a special purpose Nest.
  3. Simple (mono-media) Conferencing Applications. These use a multicast network address as their means of identifying a conference as well as transmitting their media data. These include the LBL VAT [#VAT##1#] program and the INRIA IVS program [#IVS##1#]. They need to have multicast addresses allocated per conference. Floor control, restricting which source can send at any one time, can be applied through the Notification Service and a VAT or IVS specific Nest.