To address the problem of alignment and the demands on requirements analyses for enterprise systems (ES), we suggest the optimisation of requirements analyses and thus improved alignment by formalising analyses of both organisation’s requirements and enterprise system’s capabilities with the Bunge–Wand–Weber (BWW) ontology. However, issues arise when applying this ontology to ES requirements. These issues necessitate the extension of the BWW ontology in the sense of a methodically rigorous integration of Bunge’s qualitative differentiation of ontologically distinct layers of reality. This extension of the BWW ontology, by facilitating the development of rigorous methods for the ontological analysis of ES requirements, would form the basis for evaluating the alignment of ES packages with the needs of the organisation.