Ontologies will be crucial for the future development of Next Generation Service Delivery Platforms. While various projects have defined ontologies for the mobile domain, there is yet little agreement on a common semantic model. One reason is the intrinsically hard problem of finding, using, mapping and evolving already existing ontologies. In this paper we present the Mobile Ontology, an effort within the IST project SPICE to converge towards a standardized ontology. Our approach is based on a minimal core ontology that defines common concepts for sub-ontologies of relevant domains and that is easily extensible towards existing and future ontologies. It is our intention to make this ontology available to other projects and collaboratively work on standardized ontology for the mobile domain.