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4.33 Elementary Method "PIM - Process Interaction Modeling" (PIM)  

  4.33 Elementarmethode "Proze▀interaktionsmodellierung" (PZIM)

Contents  
  • 1 Identification/Definition of the Method
  • 2 Brief Characteristic of the Method
  • 3 Limits of the Methods Application
  • 4 Specification of the Methods Allocation
  • 5 Interfaces
  • 6 Further Literature
  • 7 Functional Tool Requirements
  • 1 Identification/Definition of the Method

    /CCITT, 1985/ Annex D; pp. 189-190

    2 Brief Characteristic of the Method

    Objective and Purpose

    The method "Process Interaction Modeling"(PIM) is a semi-formal method applied for the design of the signal exchange between several communicating realtime processes. The basic method specifies which signals or data are exchanged in what time sequence between which designed processes. PIM has the character of a static rule; it only handles the sequence of the signals and thus indirectly its causal relationship.

    Means of Representation

    PIM is represented by so-called "Sequence Charts" (SQ). The following notations can be considered as examples:

    Examples for the PIM in an Ada task design are listed in /Buhr, 1984/ (p. 26-27). Examples for the process modeling with "event traces" can be found in /Rumbaugh, 1991/ (p. 87).

    Operational Sequence

    By applying the basic method, the dynamical interconnections in the process design are recorded and represented. Preparatory steps to generate the SQ (collection of signals and processes) are advisable, though not required. SQ can even be applied to find processes together with its communication requirements in a step-by-step manner, and to integrate them into a suitable causal relationship. In case the processes have already been identified and summarized in the process overview this is utilized by the method as an initial basis.

    When generating an SQ, the following steps are typically performed:

    3 Limits of the Methods Application

    The basic method must only be applied if the design comprises several concurrent processes.

    4 Specification of the Methods Allocation

    No. Activity Description
    4.1 SD4.1 - SW Architecture Design Based on the functional structure of the SW Unit the basic method specifies the signal exchange between all individual SW Unit processes as completely as possible. In this connection, the order of all signals connected with a process determines the causal dependences and sequence control in the dynamic operation, not only for each individual process but also for the overall model. Method STM - State Transition Modeling will be applied as well after the individual processes have been modeled as state automatons.

    Provided that special security requirements are not specified, the method completely covers subproduct SW Architecture.Individual Descriptions, together with STM, and completely covers subproduct SW Architecture.Dynamic Sequence Model.

    5 Interfaces

    No. Interface Observation Information in Annex 1
    5.1 PIM-PCODE The processes defined in the process interaction diagrams are taken into consideration during the PCODE generation in the detailed design. 4.15 Interface PCODE-PIM
    5.2 PIM-STM The signals or respectively the data between processes according to PIM are allocated to individual states and transitions according to STM. 4.18 Interface PIM-STM

    6 Further Literature

    /Buhr, 1984/ System Design with Ada
    /CCITT, 1985/ CCITT Annexes to Recommendations Z
    /Ko▀mann, 1987/ Entwicklung von Systemen mit einem SDL-Toolset
    /Rumbaugh, 1991/ Object-oriented Modeling and Design

    7 Functional Tool Requirements

    SSD04 - Supporting Process Modeling

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