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• Buffered online.This is like the online option. Any changes added to a specified ver-
sion are immediately sent out on the appropriate network connections, but incoming
changes are added to a different version. This is a policy that would often be more useful
in off-line collaborations, in which collaborators separately make changes but and accu-
mulate them from others in distinct working versions. It is sometimes useful to monitor
a collaborator’s activity even if one is not ready to spend time on the coordination work
required to resolve problems by executing a merge.
The policy management module may have several different policies instantiated at the
same time, corresponding to different documents, or even different modes of collaboration
on the same document. Of course, the typical application will pick one or two policies corre-
sponding to the sensible modes of interaction for its particular task, and select the proper
ones to activate automatically, or with user assistance.
7.1.3 The network manager
The policies presented above are rather weak, with each policy being a set of connections
between sources of changes, and processes that accept changes, along with a program to de-
cide which changes go to which places. That definition of policy ignores important aspects,
including all of the temporal and scheduling aspects, whatever negotiations are required be-
tween servers to determine what will be transmitted, and the like. These aspects of policy
are delegated to individual network connections, because these aspects of communication
policy and the network medium are intimately related. It is rarely sensible to use a polling
architecture over email, especially if the polling interval is short.
The concept of connection is quite general; anything that can accept Palimpsest changes
or produce them can be thought of as a connection. Some connections involve no network
activity at all, instead creating files for archival or transfer by “sneakernet.” Some signifi-
cant characteristics of network connections include:
1. Directionality.A connection can be incoming-only, outgoing-only, or bidirectional.
• Buffered online.This is like the online option. Any changes added to a specified ver-
sion are immediately sent out on the appropriate network connections, but incoming
changes are added to a different version. This is a policy that would often be more useful
in off-line collaborations, in which collaborators separately make changes but and accu-
mulate them from others in distinct working versions. It is sometimes useful to monitor
a collaborator’s activity even if one is not ready to spend time on the coordination work
required to resolve problems by executing a merge.
The policy management module may have several different policies instantiated at the
same time, corresponding to different documents, or even different modes of collaboration
on the same document. Of course, the typical application will pick one or two policies corre-
sponding to the sensible modes of interaction for its particular task, and select the proper
ones to activate automatically, or with user assistance.
7.1.3 The network manager
The policies presented above are rather weak, with each policy being a set of connections
between sources of changes, and processes that accept changes, along with a program to de-
cide which changes go to which places. That definition of policy ignores important aspects,
including all of the temporal and scheduling aspects, whatever negotiations are required be-
tween servers to determine what will be transmitted, and the like. These aspects of policy
are delegated to individual network connections, because these aspects of communication
policy and the network medium are intimately related. It is rarely sensible to use a polling
architecture over email, especially if the polling interval is short.
The concept of connection is quite general; anything that can accept Palimpsest changes
or produce them can be thought of as a connection. Some connections involve no network
activity at all, instead creating files for archival or transfer by “sneakernet.” Some signifi-
cant characteristics of network connections include:
1. Directionality.A connection can be incoming-only, outgoing-only, or bidirectional.
