There are not always cause-effect relations

Nevertheless, there are relations between the properties of the reaction system and its chemical behaviour, as can be seen firom the following example  

The fundamental molecular property underlying such an observed change of the behaviour, is the electronic distribution over the substrate. This will determine its interaction with the other constituents of the reaction system. However, this fundamental intrinsic property of the substrate caimot be measured directly. 

It is less drastic to assume that there are relations between the properties of the reaction system and the observed repsonse(s), but that these relations are not necessarily cause-effect relations. The properties of reaction space and the responses are related because they depend on the same intrinsic properties. 

This view is closely associated with the way chemists comprehend phenomena in organic chemistry. The outcome of an experiment is often explained in terms of various effects (inductive effects, mesomeric effects, steric effects etc.) which in the present context fairly closely correspond to the principal properties . 

Quantitative relations between the reaction space and the observed responses can be described as follows The data are divided into two blocks X and Y The X block contains the descriptors of the reaction system, and the Y block contains the responses observed with these systems. We are thus looking for a relation between the data structure of these blocks. 

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