15 
differentiation of the model. 
However, in view of the additional effort involved, it is obvious that a 
compromise will have to be reached in regard to the degree of differentiation 
to be employed in a particular case. In order to limit this degree of differen- 
tiation, a decision will first have to be taken as to which alternative sub- 
processes are to be included in the evaluation. The subdivision of the sub- 
processes into smaller units will then follow after an analysis has been made 
of the variations which could be expected, and which could be significant in 
each sub-process. The identification of all influencing factors, and their 
quantification or classification in terms of theoretical models, will undoubted- 
ly be one of the most difficult tasks in the establishment of production 
standards, not only in view of the large number of influencing factors, but 
also of the different groups of parameters involved in each influencing factor, 
as will be discussed below. The influencing factors themselves can be conve- 
niently grouped into the following four categories: 
* factors which are also product specifications, 
* influencing factors which are also process parameters, 
* factors pertaining to the project area, 
* factors pertaining to the executing organisation. 
As an illustration, the relation between the four categories of influencing 
factors and a selected number of sub-processes is given in matrix form in 
figure 5. 
Independent of the above classification, the theoretical models for the 
production standards will have to be designed in such a way that they contain, 
explicitly, the following three groups of parameters, (Q,) representing the 
quantitative aspects of the work (length of contour lines plotted, number of 
triangulation points used per model, etc), (Mj) representing the methodo- 
logical aspects (type of equipment used, method of organisation of work, 
etc), and (S, ) representing subjective or human aspects (skill and motivation 
of operator, etc). 
ie Production Standards = f (Q,, M,, SL) 
The numerical values of these parameters, as derived from the statistical 
processing of a large quantity of empirical data, will either be continuous 
functions of the influencing factors or discrete values representing various