Today, companies feel a need to invest in digital transformation due to changing customer demands and increasing market pressure, but at the same time also experience many challenges in planning and implementing digital transformation processes. The aim of the paper is to support digital transformation in the following two areas: 1) identification of dimensions and factors on digital transformation projects to be observed in enterprises; 2) multi-aspect digital transformation ontology formalising the elements and inter-relationships of these factors. As most of the factors are of qualitative nature and difficult to measure, the multi-aspect ontology serves as means for operationalising them. To this end, an illustrative example and application steps are presented.