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Annex 1  
4.15 Interface PCODE-PIM  

Contents  
  • 1 Characterization of the Interface
  • 2 Example
  • 3 Tool Support
  • 4 Literature
  • 1 Characterization of the Interface

    The interface corresponds to type "information transmission from one basic method to another in sequential order". The PIM - Process Interaction Modeling results are further utilized by PCODE - Pseudocode.

    In the PIM process interaction diagrams, certain courses of the modeled processes are illustrated. The sequence of the signal exchange between the processes includes a causal logic specification of the behavior, i. e. this behavior is explicitly requested by the software. The detailed specification of the behavior in the detailed SW design via PCODE must take these causal logic specifications into consideration, i. e. the sequences formulated in PCODE must be consistent to the sequences specified in the PIM.

    2 Example

    The following example illustrates the interface relationship on the basis of an example from /Rumbaugh, 1991/, chap. 5.1.2.

    Figure 4.21
    Figure 4.21: Example Process Interaction diagram for telephone call

         process PHONE_LINE 
         ...
         when STATE = IDLE
           accept dial request
              start dial tone at Caller
              set STATE = DIAL_TONE
           end
         when STATE = DIAL_TONE
           accept one digit
              stop dial tone at Caller
              set STATE = DIALING
           end
         when STATE = DIALING
           repeat
             accept digit
           until valid number is received
           start ringing at Callee
           start ringing tone at Caller
           ...
    

    Figure 4.22: PCODE Section for Example of a Telephone call

    Explanation:

    The process "Phone_Line" can be seen as a simple state automation which-as a possible execution-generates the listed process interaction diagram (see Figure 4.21 ; a state automaton with expanded features (handling of time-outs, etc.) has been listed in chap. 5.1.4 in /Rumbaugh, 1991/).

    The listed pseudocode (see Figure 4.22) accurately generates the preset sequence of the signals by permitting only certain states for the corresponding actions or by realizing the actions itself (expressed by "when..." ). In this connection, the PCODE notation follows Ada.

    3 Tool Support

    The direct mapping of process interaction diagrams into pseudocode is not supported by tools. In case state automata are explicitly generated for the individual processes, tool support is available for the mapping of state automata into pseudocode (cf. interface 4.17 Interface PCODE-STM).

    4 Literature

    /Rumbaugh, 1991/ Chap. 5 includes a number of examples about the modeling of events, states and sequences. The process interaction diagrams are referred to as "event traces".

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