A possible analogy between the designs of a technical product and of an information system.

Bojan, Ioan

Abstract: Design is a combination of science, technique, math and art, being the result of the active co-operation between a multitude of theoretical and practical knowledge. The result of the product development design is a technical product, while the result of informatics system design is an information product. The article presents a possible analogy between the two types of design.

Key words: technical product, informatics product, constructive design, technological design, structured analysis

1. INTRODUCTION

Both technical and information products have a life cycle.

The life cycle of a technical product, having in view the level of profit, the volume of production and the cost of production, can be divided in distinct stages: product definition, product achievement, launching on the market, development, maturity, saturation, decline and disappearance. One can note an obvious similitude with the biological life cycle. For the information product, the following stages of life cycle have been considered as being the most adequate (Behforooz, 1996; Lauden, 1998): opportunity study, logical design, technical design, set-up, testing, conversion and implementation, exploitation, evaluation, modification and maintenance.

In order to observe the analogy between the two types of designing we will show the content and the tools for each one.

2. APPROACHES OF THE LIFE CYCLE FOR A TECHNICAL PRODUCT

2.1 Sequence approach

In this kind of approach, the development of activities is sequential (Fig.1), due to the organization manner and the information flow between different departments of the company. The approach defines a necessary order in the development phases of the product life cycle or of its processes and also establishes the concrete responsibilities. The duration of the cycle is very long.

[FIGURE 1 OMITTED]

2.2 The simultaneous approach

This kind of approach aims at simultaneously developing some activities or at least at partially overlapping them (Fig.2). As a result, when a certain activity has enough information, it can begin; there is no need for the previous activities to be finished. This approach gains time and reduces the launching deadline and also the delivery deadline.

3. TECHNICAL PRODUCT DESIGN

The planning and development of competitive products represents one of the most important and vital tasks of a company. During the development phase, some more processes are triggered (Precupetu, 1982). First, we have the constructive design process that represents the set of activities which put to work, integrate and validate the tools and methods of design. In this stage the final conception solutions, the technical and economical performances are finalized.

The results of constructive design are: unit drawing, parts and pieces drawings.

In the frame of the technological design process all the processing and assemblage operations on the materials and parts during the production process are shown, so that we can obtain certain products or parts. The basic document in this stage is the technological file.

The overlay of some activities of the product's life cycle is shown in Fig. 2.

[FIGURE 2 OMITTED]

4. THE APPROACHES OF THE LIFE CYCLE FOR AN INFORMATION SYSTEM

4.1 The cascade model

This model is very important and assures the passing from one stage to another, in sequence order (Fig. 3). Experience has proved that the passing of stages/phases in such an order is not a rule, as in most cases we have returns to anterior stages or parallel passing of some of them.

We can meet the basic idea of this model in other models, such as the X model or the incremental model.

[FIGURE 3 OMITTED]

4.2 Competition development model

The authors of this method Coad, Yourdur and Nicola gave up the stereotypy of the steps that must follow in the design of information system and replaced these steps with activities. They consider that through the concurrent model a team accomplishes the activities of object-oriented analysis (OOA), object-oriented design (OOD) and object-oriented programming (OOP) in parallel. The model is shown in Fig.4.

[FIGURE 4 OMITTED]

5. DESIGN OF AN INFORMATION SYSTEM

We will present the "Structural analysis and design" from the information system design methods. The most widely used elements of this method are:

--Data flow diagram (DFD): a network representation of information system that contains the following elements:

a) The process: transforms the inputs in outputs. Graphic representation: a numbered rectangle, assigned through the descendent method and a clear and evident name.

b) Data flow: a channel through which known data flow. Graphic representation: a named arrow.

c) The file: a storehouse of data. Graphic representation: two parallel lines with the file name between.

Materials or / Materials /

d) The terminator: a source or a destination of a data flow. The terminators are outside the context and could be: a person, a function, a department or a company.

In one model the DFD-s are set-up on the levels:

--context diagram--DFD0--determines the boundaries of the system and shows the links with environment;

--intermediate diagrams;

--low level diagrams--the processes are functionally primitives;

The relationship between levels is a father-son relation; that means all inputs/outputs in/from the DFD-father are also found in the DFD-son, based on the data conservation principle.

The data dictionary is a storehouse in which data flow, files and even processes are defined. The symbols are:

= equivalent with; + and with; [] or; () optionally; {} iteration; ** comments.

6. CONCLUSIONS: SIMILITUDES BETWEEN THE DESIGN OF A TECHNICAL PRODUCT AND THE DESIGN OF AN INFORMATION SYSTEM

After the presentation of the content and of the results of two types of design, some analogies can be observed:

--both the technical design of a product and the information system design are top-down methods;

--both methods have as final result one product; the technical product in the first case and the software product in the second case;

--both technological design and technical design as stage in the information system design answer the question : "How must it be done?"

--both the technical product and the information product have a life cycle with well-defined stages;

--the unit drawing has as correspondent the context diagram;

--the parts drawings correspond to the intermediate diagrams;

--the piece drawing corresponds to the low level diagram;

--the table of components corresponds to the data dictionary;

--both design methods start as sequential methods and have evolved more and more into parallel methods.

7. REFERENCES

Behforooz, A., Hudson, F.J., (1996). Software Engineering Fundamentals, Oxford University Press, ISBN 0195105397, New York

Draghici, G. (1999). Integrated Engineering of Products, Ed. Eurobit, ISBN 973-96065-7-1, Timisoara, Romania

Lauden, K.C., Lauden, J.P. (1998). Management Information Systems, Prentice Hall, ISBN 0138577234, New Jersey

Oprea, D. (1999). Analysis and Design of Economics Informational Systems, Ed. Polirom, ISBN 973-683-348-8, Iasi, Romania

Precupetu, P. (1982), Industrial Technical Drawing for Machines-Building, Ed. Tehnica, Bucuresti, Romania