olemus
ISO/IEC 2382:
teenuse omadus olla saadaval kasutaja nõudel
ning jätkuda nõutava aja kestel
spetsiifiliste tolerantsidega ja ettemääratud tingimustel
=
ability of a service to be obtained at the request of the user, and to continue to be provided for a requested duration, within specific tolerances and under given conditions