The data structure is used in accessing a plurality of data files. The data stucture comprises a plurality of annotation storage areas adapted to correspond with the data files, each annotation storage area containing an annotation an annotation representing a time sequential signal and each annotation storage area comprising a plurality of block storage areas each containing phoneme and word data forming a respective temporal block of the annotation and each block having an associated time index identifying a timing of the block within the corresponding annotation. Each block storage area includes a plurality of node storage areas, each asociated with a node which represents a point in time at which a word and/or phoneme begins or ends within the corresponding annotation, and each node storage area having a time offset storage area containing a time offset defining the point in time represented by the node relative to the time index associated with the corresponding block. Each node storage area further has one or more phoneme link storage areas, each having a phoneme storage area containing data identifying a phoneme associated with corresponding node; or one or more word link storage areas, each having a word storage area containing data identifying a word associated with the corresponding node. One or more of the node storage areas has at least one of the phoneme link storage areas and at least one of the word link storage areas.