This paper discusses an ontologisation of a subset of the Telemanagement Forum's New Generation Operational Support Systems standards. The result is a set of ontologies, each corresponding to a particular element in the set of standards, covering complementary aspects of the telecommunication domain. These ontologies are articulated in a modular way according to the standards they target. The ontologies are also mapped, again, in ways adapted from the correspondences put forward within the set of standards itself. We show that ontologisation of informally or semi-formally laid standards can involve non-trivial ontological engineering choices. In addition to sharing lessons learnt, our aim is to support the view that the production of ontologies issued from standards is an endeavour that has the potential of furthering and enhancing standards' development, their dissemination, and operationalisation. Ontologisation of standards, we believe, should be part of the standard development lifecycle.