Clarifying SIP 2.0 and dc*.xml files?

[netsensei]

The 2.0 specification specifies a naming convention for descriptive metadata files: dc+schema.xml and mods.xml. The spec suggests that the conventions can be loosely interpreted when it comes to files containing Dublin Core structured metadata.

In this section following suggestion is made:

If descriptive metadata is available for a given IE, a link is established via a shared ID between the relevant PREMIS object in the premis.xml file and the corresponding descriptive/dc*.xml file.

Further down, a section about the <dmdSec> element gives this concrete example: xlink:href="./metadata/descriptive/dc_1.xml"

Whereas the profiles defined in the 2.0 specification don't seem to go beyond the existence of dc+schema.xml files for both the Basic as well as Material Artwork profiles.

Moreover, the Material Artwork definition seems to contradict the possibility of having multiple descriptive metadata files::

There MUST be exactly one IE at the root. There MAY be other sub-IE’s that are part of the root IE or other sub-IE’s (e.g. to describe panels of a triptych individually).

So, this allows for the existence of multiple IE's. (sidenote: it's unclear what is meant by the second "other sub-IE's" if there's only exactly one IE at the root)

However, this line under the "Descriptive metadata" heading suggests that there's only a single IE which should be described in a dc+schema.xml file.

A descriptive metadata file descriptive/dc+schema.xml describing the IE MUST be present at the package level.

Also, the naming of the files creates a link between the contents and the schemas used to structure the content. e.g. dc+schema.xml seems to indicate that the file contains both dcterms as well as schema.org properties. However, if multiple dc*.xml files may exist. Does this imply it's possible to create valid combinations such as dc+schema_3.xml indicating that this file contains metadata about a third IE inside the package having both dcterms and schema.org properties?