A method is provided for securely delivering identity data units over a communications network to a client device. This effects a simple construction that is efficient for cooling an NMR apparatus. The present invention also provides a method and apparatus for monitoring an electronic communication utilising the above dictionary. The media player is then instructed based on the metadata to access and appropriately place the branding elements in or outside of the video rendering window. A controller, upon outputting an electronic document as audio from the audio output unit using speech synthesis, when the electronic document contains the word stored in the storage unit, controls the audio output from the audio output unit according to the type associated with the word. The method includes declaring one or more class structures in databases having metadata describing characteristics defining the class structures.