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ComputerAided_Design_Engineering_amp_Manufactur.pdf

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n g<br />

n j<br />

Definition: The and of a TT (PP, TP, and PT) generation are transition (place, transition, place)<br />

and transition (place, place, and transition), respectively.<br />

For factor 2, ng and nj can be in the same or different PSPs. For the latter case, there are five possibilities:<br />

(1) sequential earlier (SE), (2) sequential later (SL), (3) concurrent (CN), (4) exclusive (EX), and (5) cyclic (CL).<br />

Definition: Let �g ( �j) denote the PSP that contains the generation point (joint). Pure generation (PG)<br />

generates paths within a single PSP (Figure 8.2), i.e., �g � �j . Interactive generation (IG) generates<br />

paths between two PSPs (Figure 8.4), i.e., �g ��j .<br />

Definition: If ng → nj prior to the generation, then it is a forward generation; otherwise it is a backward<br />

generation.<br />

In Figure 8.2, [t1 p4 t3] is a forward generation; �6 in Figure 8.4(a) is a backward generation. A<br />

backward TT generation needs the addition of tokens to the NP to avoid the resulting N being nonlive.<br />

This constitutes Rule TT.2.<br />

The idea of constructing the rules is simple. An eligible generation upon N to produce should<br />

not alter the marking and firing behavior of . Furthermore, the new PSP must be live and bounded.<br />

One of the following three actions is taken depending on the type of generation: (1) forbidden,<br />

(2) permitted, or (3) permitted but need more generations. For instance, a TP generation causes<br />

an extra token to be injected into the original net whenever the NP gets a token. This alters the<br />

marking behavior of and the net is unbounded. A PT generation robs a token from and<br />

causes to be nonlive, hence changing its firing behavior. To avoid this problem, add more<br />

generations or forbid such generations. The rules are complete in the sense that all possible generations<br />

have been considered.<br />

The following definitions for TT and PP rules have considered all possible structural relationships<br />

between and . Some generations are forbidden, some require the addition of tokens, while others<br />

require further generations.<br />

1<br />

N 2<br />

N 1<br />

N 1<br />

N 1<br />

N 1<br />

N 1<br />

ng nj Definition: TT Rule:<br />

For an NP from tg � �g to tg � �j generated by the designer,<br />

(0) TT.0 If tg � tj or only one of them is in a cycle, which was solely generated using Rule PP.1, then<br />

signal “forbidden, delete the � ” and return.<br />

(1) TT.1 If � , signal “a pure TT generation;” otherwise signal “an interactive TT generation.”<br />

(2) TT.2 If ← , signal “forming a new cycle.”<br />

If, without firing , there does not exist a firing sequence � to fire , then insert token in a<br />

place of NP.<br />

If � , return and the designer may start a new generation.<br />

(3) TT.3 If the structure synchronic distance � � then<br />

(a) TT.3.1<br />

Apply Rule TT.4.<br />

(b) TT.3.2<br />

Generate a new TT-path path to synchronic and such that after step 3.c,<br />

changes from � to 1.<br />

(c) TT.3.3<br />

Go to step 2.<br />

(4) TT.4<br />

(a) TT.4.1<br />

Generate a TP-path from a transition of each in to a place in the NP.<br />

(b) TT.4.2<br />

Generate a virtual PSP, a PT-path, from the place to a transition of each in .<br />

w<br />

�g �j tg tj tj tg �g �j s<br />

dgj s<br />

tg tj dgj tg �g Xgj pk n˙ j tj �j Xjg Definition: PP Rule:<br />

For an NP from pg � �g to pj � �j generated by the designer,

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