1. A method of retrieving a plurality of resource fragments from a audio-visual resource that is encoded using a hierarchical addressing model for the class of resources of which the audio-visual resource is a member, the method comprising the steps of: inputting a URI reference comprising a Universal Resource Identifier and a complex fragment identifier comprising a plurality of audio-visual resource specific location steps; locating the audio-visual resource using the Universal Resource Identifier; establishing a logical representation of the structure of the audio-visual resource; and iteratively evaluating the fragment identifier location steps against the logical representation to resolve the complex fragment identifier into a set of explicit fragment references configured to explicitly address each of the plurality of resource fragments of the audio-visual resource.