A system developing model for process control systems

Copyright © IFAC PRP 4 Automation, Ghent, Belgium 1980

A SYSTEM DEVELOPING MODEL FOR PROCESS CONTROL SYSTEMS I. Westhagen Systemutvikling A.s., Oslo 3, Norway

Abstract. Developing process control systems,based on computers, is a compl,cated affair when you have to be concerned about the fact that the system shall meet the needs of the workers,thelocal labour union and the company leaders. And this needs cannot be met if the different parts are not involved in the system developing process. To manage the whole developing process under this conditions,it is to great help using a system developing model that can guide us into the different necessary stages of the developing process. The article describe such a model and the conditions why itis necessary (in Norway) to use certain models,methods and techniques in the developi ng process. Keywords. System developing model ,methods and techniques,end user involvement and demands,conditions for the system developing work,system quality, society requirements for how the developing process should take place. INTRODUCTION The system developing process can be illustrated as seen in fig. 1. All work that have to be done between an idea or a need comes up to a complete computerbased system is ready for use in the factory. I am going to talk about a model and some methods that can help us in controlling this work from a to z such that certain requirements are fulfilled. THE REQUIREMENTS AND PROBLEMS CONNECTED TO THE SYSTEM DEVELOP-ING WORK There are at least three important classes of requ i remen ts: 1.The requirements of the society described in the workers security law and agreements between labour union and the union of employers. 2.The end users requirements to the system quality.The system has to fulfill needs of different parts. 3.The usual requirements of holding cost and time for the developing work within certain limits. A system developing model should take into ac~ Count all these three classes of requirements. But to ma ke it cl ea rat once: It is impos sib1e to take care of all this with just formalized methods. The system developing process is (or Should.be) a social process. The ability to communlcate and cooperate with other people in a development process,can never be sUbstituted

THE PROCESS IDEA------------ CONTROL a z SYSTEM Fig. 1. The system developing process by formalized methods,but such methods can be an important help in the communication process. Before describing the model,I will explain more in details the three classes of requirements and the connected problems mentioned above. The requirements of the society The paragraph 12 in our worker security law says: the workers shall take part in the system developing process.-and ---technology shall be developed in such a way that unwanted physical and/or phsycological impacts on the workers do not occur.-There should be quite clear that these statements must have concequences for how the system developing shall take place. But the law does

I. Westhagen

170

not give any description (of course) of how this work should be done in practise. If we really want to have active involvement from and cooperation with the workers in the system developing process,we have to understand and accept the following: The end users represant a valuable resource which is important to make use of in the system developing process. There will be of no use just to fullfill the law literally - because that will not make the most of the resources mention above. The system developing model and methods must therefor be of such a kind that they not only meet the needs of the experts,but also the users requirements. The methods must not exclude the users from taking part in the developing process,but rather stimulate the developing process to be a good social process within the factory. The law states that job enrichment is important.It means that when developing computerbased process control systems,it is necessary to take care of all factors that have impacts on the working conditions.And we all know that process control systems have great impacts 1i ke: - taking away certain jobs - making changes in working organization - centralizing control operation - work quality polarization The problem is that we don't know for certain how to take care of these aspects in the developing process. But we do know that cooperation with the workers are important. We also know that these problems must have consequences for the system developing methods. Some empirical materials we do have.It is clearly,for example,that organization development must go hand in hand with the system developing work. This means that there must exist a mandate for and an occasion to work with organizational aspects.To summarize the conditions the system developing methods must take into account: - The methods must stimulate,not exclude, the users involvement such that the resource they represant is used in the developing process. - The the ing ing

methods must be able to integrate organizational and system developwork such that the quality of worklife is enriched.

The system quality requirements Taking care of the system quality is a question of: - Do we do the right things? and Are we doing things right? Answering the first question with "yes" is necessary before we care about the second one. But to answer the first question we have to

answer this first: Who is going to answer? Again we can see that without t('vlng the end users into the developing process - all from the very beginning it is impossible to meet the real needs of the users.This make setting of objectives to the most important thing in the developing cycle. Primarily it is not the experts needs that shall be satisfied,but the end users. Of course there may be possibilities that the users are not able to see. Then it is the experts responsebility to tell ,but not to decide. The role of the expert have to change. Normally there is not possible to build a process control system on just objectives. These are usually not operational.Detailed specifications have to be worked out before the system can be constfucted.These specifications - .called users demand specification (UDS) - shall represant the systems outer attributes. There should be quite impossible to control that we aredoing the right things,and that things are being done in the right way without these specifications. The system developing model must lead the developing process in such a way that these UDspecifications are being worked out. The economic and timeschedule requirements The problem with holding the cost of the developing work down is well known.But there should not be overseen that the maintenance cost is often higher than the developing cost. The system developing model and methods should therefor help us in holding both the developing and maintenance cost down. I have now presanted the main requirements and conditions under which a computerbased process control system must be developed and constructed. The system developing model I am going to describe in the following,is a result of different research projects I have been involved in and my own expierences in this field. THE SYSTEM DEVELOPING MODEL A model that covers the whole developing process must be quite large.Therefor it is not possible to give more than the main frames o~ the model here.Specially it will not be posslble to describe the different methods and/or techniques that are used in the varies phases of the model. The main outline of the model are shown in fig. 2. The characteristcs we can see out of t his i 11 ust rat ion of the model , is: - The model describe a pha'~-0riented developing process with emphasize on the problem- and analizing part of ~the process. - The model indicate an iterative developi n9 pro cess. - The model require documented results of each phase.

A System Developing Model

rlla 1 n aC1 ti vi ty I type

r~a in

phases

Main results

Prob 1em oriente system work

r

of phase one: Description of the situation Problem describtion Description of objectives Efforts description

PHASE TWO: NEEDS ANALYSIS SUbactivities:a)Design new work organisation and routi nes -work separation man/maschine -designing jobs -specify information requirement -design control room

::s:~~: oriente system work

Result a) b) c) d)

171

b)specify the rules for information processing c)specify the actual control theory to be used. Measuring specification.

Detailed construction

1

f

t1 Sys tern i

into opera._t_i_on_ _.-..

d)logical data structuring e)specify integration with other systems

Fig. 2. The main outline of the system developing model To understand the model we have to look inside the main outline given in fig. 2.And we must all the time remember the requirements and problems I have described before PHASE ONE: PRODUCTION AND PROCESS ANALYSIS Subactivities: a) Analyzing the situation -the process -the production equipment -the existing control system -the working routines -the quality of working life -the level of competance -the production economi b) Analyzing the problems -identify concerned parts -gap analysis -problem priority c) Setting objectives d) Decide the efforts to be done -alternatives -analyze the consequences rough ly Methods:

a)-process flowchart mathematical models -drawings -wallgraph -questionnaire -verbal expression b)-Kepner-Tregoe -tabel s c)-verbal expression d)-verbal expression

~11ethods

:

a)-wallgraph -simulation -display picture drawings -report drawings -ergonomi cs b)-differnt mathematics -verbal instructions c)-cybernetic methods d)-data base technique e)-verbal instructions

Result of phase two: A user demand specification document PHASE THREE: SYSTEM CONSTRUCTION Subactivities:a)Evaluate system architecture -centra 1i za t ion -distributed -security evaluations b)spesify the instrumentation c)spesify the computer equipment, terrlli na 1s etc. d)evaluate cumputer delievery companies e)analyzing the concequenses -economically -technically -organi za tiona 1 f)select the proper alternative g)plan education activities

I. Westhagen

172

Methods:

Verbal expression and tabels

work organization the people in the factory want,before the start of the system construction work.

Result of phase three: A system specification document

-The model also emphasize the results of the developing work in the different phases shall be documented successivly.

PHASE FOUR: DETAILED CONSTRUCTION Subactivities:a)structuring -program structure -data structure -communication structure b) programmi ng -flow Chart drawing -coding -testi ng c)educate the operaters

The model furthermore show us that the typical cybernetic problems usually represant a small part -and also often small problems- against all other problems that must be taken care of in a practical developing process. We must all the time remember that the result of the developing process is of little value if it does not meet the needs of the end use~s. It is of little help that the system is a very technically advanced system if the users won1t use it. ·

d)design the work routine in deta i 1 HOW SHOULD THE MODEL BE USED ? e)installing the instruments f)planning the system test Methods:

a)data base techniques communication protocols b)different computer language and coding procedure -fortran,assembly,JSP,APL,etc.

Result of phase four: System documents and a lab. version of the system.

The model as described is a maximum model.Depending on the actual situation,the different activities will require more or less work.Or they can be out of question at all.What is important is that we have to take a conscious decision about an activity should be worked out or not. An interesting question is:When and how should the workers in the factory take part in the developing process with reference to the model? The intensity of the user involvement should after my opinion,be as illustrated in fig. 3. Intensity of users pa rt i c i pa t ion

PHASE FIVE: SYSTEM INTO OPERATION Subactivities:a)system test

'.

users

b)acceptance test c)get the new work organization into operation d)educate operators No formalizing methods is used

Result of phase five: A complete system documentation and a system in operation The model presented above will not - in itself - fulfill the conditons described in the beginning of this artcle. But it will help very much. The main thing is how the model will be used in practical developing work. In addition to the characteristica I mention above,I will underline the following: -The model emphasize finding the right work separation between the man and the maschine.And from this design the

-

1\

experts 1

_or

_ _---I..'

Methods:

'"

2

3

- - ' -_ _----'~

4

1110 d! 1 )-

5 '________

______41

Pha ses

Fig. 3. Users and experts partisipation in the system developing process To secure user participation in the system developing process,the developing methods must not represant a difficult learning process for the users before they can start on the real work of developing the system. If sO,that will destroy the users possibility to take real part inthe developing process and they will very soon withdraw -more or less frustrated.And certainly they will be negative to what is going on.This statement may be seen as if the users prevent us from using advanced methods. This is not true. What the users are interestd in is the systems outer attributes.And it i~ possible to describe the outer attributes wlthout making use of difficult methods.

A System Developing Model

Organizing the system developing work in a proper way under this circumstanses and requirements,may be difficult.At first,the users must get time to involve themselves in the process. This means that some of their daily jobs must be transferred to other.And this usually means difficulties. But if the users of the system have to work with the system developing problems in the evenings and when they are off the job,itis imp~ssible to get anything but frustration out of It. When the users have got the right terms for doing a job in the developing process,it is rather efficient to organize their participation in socalled working groups.It is in this groups -where both the users and the experts take part - that mo st 0 f the act i vi tie s descri bed i n the system developing model,phase 1,2 and 3, are going on. CONCLUSION A system developing model is a necessary common platform for the different parts to comminicate on.It is necessary because developing a co~puterbased process control system concern many different people in the factory - and their views and interests are not the same as those of the experts or the leaders in many aspects.As mention before, I also mean such a model is necessary to fulfill the requirements described in the beginning of the article.It is a fact that we ,are not abl e to manage the different aspects connected to the technollogy impact on the quality of working life. In spit of this,there exist not any accepted model for doing system developing work in this field. Each one has adopted their own model or method -if any at all. This is not good enough. I hope that this article will represant a start on a broader discussion and research work for finding good system developing methods. There is a lot of work yet to be done. As I said before, the goal is not to find a model that means that the system developing work can be automated. That is not possible or wanted. The main thing is to be able to manage the developing process so that the negative concequences are minimized without taking away the positive concequences. REFERENCES There are little or no litterature in this field on system developing models and methods In the field of developing administrative information systems there is a lot of litterature but this is not all relevant to our field.

173