In this paper, we discuss the use of ontologies for semantic business process management. In particular, we address system and process integration challenges encountered in the real world, based on the example of the telecom domain: Internet-based telephony service (Voice over IP). Various aspects of ontology development are covered including relations to industry standards, ontology creation methodology and practice determined by telecom-specific aspects. Based on the use case example and the YATOSP framework, we ar-gue that the economical justification of the development of domain ontologies, due to their complexity and numerous dependencies, is not straightforward.