The full taxonomic hierarchy of the included taxa/items certainly must be supported by the standard (and it will be addressed after we deal with simple characters, states and items). If the creator of the dataset doesn't think it's important then they can choose to leave it out; if the user of the data doesn't think it's important then they can ignore it. This will be especially important if we intend to support inheritance and compilation up and down the classification (as has been suggested by several of us).
Jumping the gun a bit, I would think these relationships would be stored either as a separate nested set of elements with ID's linking to specific items, or the items themselves would be nested with parent items containing their children.
Steve Shattuck CSIRO Entomology biolink@ento.csiro.au