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Instantaneous Description

An instantaneous description formally describes the state of a CP instance at a particular time. An instantaneous description of a CP instance tex2html_wrap2340 is a 7-tuple:

displaymath2471

such that:

tex2html_wrap2454 is the originator agent; tex2html_wrap2455 is the helper agent; tex2html_wrap2340 is the polarity of the CP instance; tex2html_wrap2457 is the current setting of transport policies; tex2html_wrap2458 is the current state of the finite state control; tex2html_wrap2459 represents all utterances currently kept by the input list; and tex2html_wrap2460 is the current state of the pushdown list.

Figure 3 depicts a partial instantaneous description for an instance of the CP DBP employed by a trading interagent to allow its customer (a buyer agent) to participate in a bidding round open by the auctioneer agent. We identify buyer Akira as the originator, the auctioneer as the helper, and the colored node tex2html_wrap2461 as the state of the finite state control.

A deterministic CP has at most --without taking into account possible e-moves for dealing with expired utterances-- one possible move from any instantaneous description. However, continuously traversing the input list in search of an utterance that causes a transition can lead to race conditions. For instance, in the CP instance of Figure 3 the second and fourth utterances can originate a race condition since both utterances can cause a move in the finite state control. Thus, it is necessary to define criteria for deciding which utterance must be accepted as we show in the next section.



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Wed Mar 10 11:44:57 MET 1999