1. A method for provisioning in communications, data or service networks ( 1 ), the method comprising steps for receiving at least one request form a client system ( 11 , 30 ) through an Application Program Interface (API, 12 , 13 ) for defining measures relating to customers and/or services and/or network elements ( 18 , 19 , 20 , 21 , 72 ), processing ( 14 ) each request in functional layers ( 80 , 81 , 82 , 83 ) of the provisioning system hosted by network operator ( 1 , 2 ), executing tasks according to the results of the processing step, and reporting the results to the requesting entity, characterized in that service operators ( 3 , 4 ) are allowed to use the provisioning system ( 15 ) through authenticated Application Program Interface (API, 40 , 50 ) and Management User Interface ( 48 , 49 , 58 , 59 , 93 ) and authorisation function ( 43 , 53 ) after the provisioning rules processing ( 94 ) where the rights for the use of the network elements ( 18 , 19 , 20 , 21 , 72 ) are controlled by the network operator, whereby the network operator is able to present and utilize one physical network in many logical views, each representing the portion accessible for virtual operator, and in this way controllable by network operator with limitations, authentication and authorization rules.