1. A computer-implemented method of determining explicit fragment references for a plurality of resource fragments of an audio-visual resource, wherein the resource fragments can be addressed using a hierarchical logical model for classes of resources of which the audio-visual resource is a member, and wherein the explicit fragment references are configured to direct at least one of a process and a device to each of the plurality of resource fragments, the method comprising the steps of: (a) inputting a URI reference comprising a Universal Resource Identifier and a complex fragment identifier comprising a plurality of audio-visual resource-specific location steps; (b) determining an audio-visual resource location using the Universal Resource Identifier; (c) constructing an XML (eXtensible Markup Language) representation of the audio-visual resource based on the hierarchical logical model and information collected from the audio-visual resource location, the hierarchical logical model being used to create the explicit fragment references, wherein the XML representation of the audio-visual resource includes XML elements and XML attributes that correspond to a super-set of the resource fragments of the audio-visual resource that are addressable by the complex fragment identifier using an extended Xpath addressing scheme; (d) evaluating a current resource-specific location step of the resource location steps against the XML representation of the audio-visual resource, the resource location step having a temporal or spatial axis, a node test and at least one predicate, the evaluating step comprising the steps of: (d-1) selecting a set of nodes in the XML representation of the audio-visual resource dependent upon the current location step, said selected set of nodes representing the explicit fragment references; and (d-2) projecting the selected set of nodes to the temporal or spatial axis specified by the current location step; (e) modifying an XML representation of the selected set of nodes, when the current location step is for one of a spatial or a temporal axis, said modifying step comprising the steps of: (e-1) evaluating the node test of the current location step to select the projections of the nodes on the axis; (e-2) adding XML special attributes to the XML representation of the selected set of nodes; and (e-3) applying the at least one predicate to refine the selected node set according to the added XML special attributes; (f) selecting a next resource specific location step from the resource location steps as the current location step; and (g) repeating said evaluating step (d) and modifying step (e) to provide a targeted degree of resolution for resolving the resource-specific location steps into a set of the explicit fragment references.