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Graphical user interface

The graphical user interface manages the complete user interaction. It supports:

The model description process consists of several main steps.


The net's graphical representation is clearly dominated by the Coloured Petri net part. This part is specified by creating and positioning places and transitions and establishing their connections by directed arcs. Figure 3 shows the net corresponding to Example 1.


Attributes of places and transitions have to be set. This includes entering the different colours in a list, choosing the type of transitions and places (timed or immediate, resp. timed or ordinary) and fixing the number of tokens for the initial marking. Especially timed places require some additional information:

  1. for each colour
    1. its rank according to bulk arrivals
    2. its service time distribution specified by its mean and coefficient of variance. This service time distribution is approximated by a Cox distribution as described in [8].
  2. scheduling strategy
    Presently available scheduling strategies are FCFS, LCFS-Pr, PS and Infinite Server (IS).
  3. number of servers
  4. performance figures
    to be determined in quantitative analysis (cf. Sec. 3.2.4).
Figure 5 displays attributes for Station_1 of example 1.


The incidence functions of the Coloured Petri net (cf. [10]) have to be specified. This is possible in a graphical submodel at each transition. Such a submodel describes the locally unfolded net regarding a single transition and its input and output places. A special feature of QPN-Tool fills the submodel automatically with the transition's colours and all input and output places including all of their colours. Thus only arcs and their weights have to be specified manually.

Figure 6 shows the submodel of transition Fork in Fig. 3. A rhomb represents a coloured place. Colours of a place are represented by circles which are connected to its corresponding place by lines. Bars display colours of the transition whose submodel is regarded. Obviously transition colour `fork_light' takes one `light' token from place `Station_1' and puts on places `Wait' and `Station_2' one token on each of the corresponding colour `light'. Transition colour `fork_heavy' does the same for `heavy' tokens.

Locally unfolding a net has certain advantages:

Since locally unfolding is used within QPN-Tool, it combines a comfortable description technique with a clear presentation.

Next: Analysis techniques Up: QPN-Tool Previous: QPN-Tool

Tue Jan 9 09:20:20 MET 1996