A.F. Kolchin ANALYSIS OF DESIGN TASK

A.F. Kolchin ANALYSIS OF DESIGN TASK

The designing is usualy viewed as a process based on the transition from the universe of design specifications to the universe of objects or components i.e. the process of complete specification of a set of primitive components and their relations.However, this definition does not contain the goal, the designer aimed at. Let us consider a goal as the description of requirements which are implemented by the object under design i.e. they are the part of specification.

The problem of designing is transformed to the design task if some strategy or method which makes possible to transfer from specification of object under design to the object itself is given.

The report describes well known general method for design problem class which is called “propose – critisize - modify” (PCM method). Generaly speaking PCM method is the general template comprising the following method classes: a) methods proposing complete or partial solution; b) methods checking proposed solutions and analyzing (critisizing) propositions to discover the causes of specification violations if they are exist; c) methods modifying propositions in order to fulfil design goals. The analysis of real tasks shows that the class of methods proposing solution can be didvided into methods based on 1) problem decomposition and solution construction; 2) design plans and 3) modification of available solution. In this study the analysis of described above method classes, used in design tasks, is done; the type and structure of used knowledge are defined; their functional structures are built; behavioral structures are proposed.

It is proposed to divide the multitude of design tasks into four classes (depending on whether or not a) object structure; b) components the object consists of; are initially defined for object under design): parametric design, configuration design, skeleton design and creative design.

The analysis of parametric design task is presented in the report. Well known refinement of PCM method for parametric design task (which is called “propose and revise”) is discussed in details. It is shown that this method may be decomposed into four following tasks: select parameter, propose parameter’s values, check constraints and correct detected constraint violations. In turn, the last subtask may be also decomposed into smaller subtasks and so on until all subtasks become elementary. For every subtask requirements are defined which are imposed on the structure and type of domain knowledge, used by subtask. All these requirements make possible to form restrictions and usage conditions for the whole method. On one hand this makes possible to create method (or its modification) selection criteria, based on goals of the design problem which is solving; on the other hand to answer the question how necessary domain knowledge should be interpreted and represented. This method independansy of particular problem (but not of the class of problems) and domain knowledge used makes possible to create the library of such methods and their modifications which is one of the key modules of toolkit for construction of intelligent design systems which is under development now.

I. A .Kalabanovsky, A.F.Pohilko DATA PRESENTATION AND CRITERION OF INVESTIGATION OF CAD-SYSTEMS FOR THE CLASS OF PROBLEMS WITH THE STRUCTURED PRESENTATION OF DATA

In the area of industrial design one of the most wide-spread problems is the design of equipment from the kit of standard details and components. Moreover, linking of components is done by elementary mathematical formulae and functions. In a process of automated design all components of designing object are displayed through several aspects[1]:

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  Tabular aspect of presentation;
  
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  Graphic aspect of presentation;
  
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  Textual aspect of presentation;
  
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  Mathematical aspect of presentation.
  

To refer the process of design to the class of problems with outline(structured) presentation of data, it must correspond to the following criterions:

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  design of an object is basically produced of standard details and component;
  
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  using of the non-standard details is reduced to minimum,
  
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  non-standard details and components are designed by other organizations or groups of designers, not in accordance with design of the main object;
  
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  non-standard details used in design are taken as united indivisible components with determined working parameters, non-changable during the design process.
  

The result of some design task, refering to class of problems with structured data, would be the system of decisions, strictly keeping three main decision principles for the problems of the given class:

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  Principle of casuality, i.e. all system components are casually bounded by the relations leading to the decision of the problem;
  
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  Principle of modality, i.e. all actions of process of design are produced consecutively from the initial to the final stage and lead to the final objective of design;
  
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  Principle of modifiability, i.e. any structural modifications of the task should not break the principles of casuality and modality.
  

1. 
   Pohilco A.F. Technolody of development user-orinted CAD-applications. International Conference INFORMATION TECHNOLODY IN DESIGN. Proceeding. 1Moscow. IESTI, 1996.
   
2. 
   George J. Klir. Architecture of Systems Problem Solving. State University New York at Binghamton. Plenum Press. New York. 1985.