Late Join (English "late entry ") designates the late joining from users in computer science to a which is running meeting of a computer application to the group work (Groupware).

The occupation with problems and solutions in connection with Late Joins is one of the tasks computers of the Supported Cooperative Work. As in a material meeting the question arises, how the members that were added again can be brought as fast and comprehensively as possible on the current conditions to the work. In the specialized terminology it concerns the efficient completion of an Late Join inquiry of a Late Join Clients, by by one or more Late Join servers Late Join data are conveyed to it. Thereby the following optimization criteria are to be considered:

• Initialization delay. The temporal duration to the new users in the meeting to participate actively to be able should be as short as possible.
• Network load. The network should be loaded by the entry if possible little.
• Application complexity. The algorithms, which manage the initialization, should be as simple and fast as possible.
• Robustness. The initialization should run off as faultlessly as possible.
• Consistency. After conclusion of the initialization the new users on the current conditions and in the possession of all necessary data should be.

Problems, which work against an optimal fulfilment of the criteria, are:

• Late Join servers experience additional working load by the initialization. The selection of a suitable Late Join server can be time-consuming and affect negatively thus initialization delay and application complexity. If a server is selected by mistake, which is not even on the current conditions, the consistency is in danger.
• The range of the Late Join data can fail with large systems very largely, which can affect initialization delay, network load, application complexity and robustness negatively.
• The time of the initialization should for the minimization of the initialization delay be as early as possible, could however possibly in a later dwell phase substantially more efficiently be completed. Also the question arises whether the Late Join Client receives all Late Join data immediately or these are only gradually sent away arranged according to criteria for choice.
• Transfer errors weaken the robustness and increase by the necessary corrections or repeated transmissions the network load.

As solutions for these problems the following possibilities offer themselves:

• Complete or partial initialization. The range of the Late Join data with a complete initialization (with that the Late Join Client all available data receives) can be reduced or graduated at least, if it receives first only the straight necessary data and additional data only if they are needed. The selection of the data is managed over so-called Late Join Politiken.
• The kind of the Late Join data can be varied between history, condition or a combination of both. In the case of initialization by a history all operations of all participants implemented so far are conveyed to the Late Join Client; since actions are cancelled often or overwritten several times, here usually much redundancy results. The initialization over the current condition does not contain this redundancy, however usually the transmission of very many data needs. With the combination first an older condition and afterwards all operations implemented off there are conveyed.
• The initialization can be implemented over Unicast or multicast. By Unicast initialize exactly one Late Join server exactly a Late Join Client, while by multicast a Late Join server several Late Join Clients can initialize at the same time - under additional load of some further group members.

Articles in category "Late Join"

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