Network Primitives

In some sense, the network primitives are the most interesting aspect of PLAN, as they enable mobile computation via generating and sending new active packets.

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  The first basic network primitive, OnRemote, is quite general, and we expect that convenient shortcut versions of this primitive (with some of the arguments implied) will be built on it eventually. Its syntax is: OnRemote( E, H, , )

  The meaning of this primitive is: evaluate E on host H. Furthermore, use the function to determine how to get to H. Finally, the current packet donates of its resource bound to the child packet.

  More specific restrictions follow:

  • E must be a function call . The arguments will be evaluated at the current node yielding .
  • H is an expression of type .
  • is an integer indicating how much of the parent's global resource bound should be transferred to the child packet.
  • should be a function or service of type . should return some host which is a neighbor of the current node (with the idea being that is the next hop on a route to h in the routing scheme represented by ).

  On success, the call to OnRemote will create a PLAN packet which is sent to . The invocation part of the PLAN program consists of and the code part consists of the subset of the code of the invoking program that is required to properly evaluate the invocation. The remainder of the packet is defined by the remaining three arguments to OnRemote. Within the currently executing program OnRemote returns unit.

  In the event of an error, one of the following exceptions will be raised (and the creation of the packet aborted):

  • NotEnoughRB will be raised if exceeds the parent packet's current resource bound.
  • HostNotLocal will be raised if the function maps H to a host which is not a neighbor of the current node.

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  The second network primitive, OnNeighbor is similar to OnRemote, with the restriction that the generated child packet must execute on a neighbor of the current node. The syntax is: OnNeighbor( E, H, )

  Here, we want E to be evaluated on H (a neighbor of the current node), and of the current packet's resource bound will be transferred to the child packet. More specifically:

  • As with OnRemote, E must be a function call . The arguments will be evaluated at the current node, but not the actual call to f.
  • H is a expression of type , and must be a neighbor of the current node.
  • is an integer indicating how much of the parent's resource bound should be transferred to the child packet.

  On success, the call to OnNeighbor will return unit. In the event of an error, one of the following exceptions will be raised:

  • NotEnoughRB will be raised if exceeds the parent packet's current resource bound.
  • HostNotLocal will be raised if H is not a neighbor of the current node.