In this paper we introduce a complex procedure of reducing dimensionality of multidimensional data series. The procedure consists of several steps, and each step gives a new data series representation as well as dimension reduction. The approach is based on the concept of data series aggregated envelopes, and principal components called here 'essential attributes' generated by a multilayer neural network. The essential attributes are generated by outputs of hidden layer neurons. Next, all differences of the essential attributes are treated as new attributes. The real values of the new attributes are nominalized in order to obtain a nominal representation of data series. The approach creates a nominal representation of the original data series and considerably reduces their dimension. Practical verification of the proposed approach was verified for classification and clustering of time series problems, the results are set out in different papers of the authors. Here, the short summarization confirms utilities of time series dimension reduction procedure.