A sequence is an abstraction used to assign numbers to items of the same or similar type throughout a document. This page summarizes how sequences are defined by the OpenDocument standard. Much has been filtered out, but I believe this to represent a reasonably complete synopsis of the role of sequences in terms of both their function and their presence in an OpenDocument file.
The information on this page came from the first committee draft of OpenDocument Format v1.2, released Feb 16, 2009.
This page collects information about how the OpenDocument text file format records structure in the document. Also included is information about how structural information is displayed. Much has been filtered out, but it is my belief that this subset represents the core of document structure in the OpenDocument text format.