A method of operating a communications network is disclosed. In order to manage a network, it is first necessary to establish the state the network is in. This is difficult in practice because the network operational data stored and transmitted in the network takes a myriad of forms owing to the variety of suppliers and types of network equipment. There is a need to distil that network operational data down to aggregate network operational data which can be taken to provide an indication of the state of the network which is of a manageable size, and to which network management apparatus can react by sending control commands to the network. The problem of generating aggregate network operational data is tackled by identifying the type of each attribute found in each network operational data item, and classifying the network operational data items in a manner which takes account of the identified types and thus provides network aggregate data which more accurately reflects the operational state of the network. This in turn leads to the network management apparatus controlling the network to operate in a more efficient manner than has hitherto been possible.