Data structure to store information about an external reference. An
external reference can be either a single cell reference, a cell range
reference, or a named range.
Index of an externally linked document. Each externally-linked document
has a unique index value.
You can get the index value of an external document from the
corresponding ExternalDocLink
instance through its attribute com::sun::star::sheet::ExternalDocLink::TokenIndex.
Name of the sheet that the external reference points to.
In case of a cell range reference that spans across multiple
sheets, this is the name of the first sheet in that range.
Note that an external range name ignores this value at the moment,
but it may make use of this data in the future when Calc supports a
sheet-specific range name.
This can store either SingleReference for a single
cell reference, ComplexReference for a cell range
reference, or simply a ::string for a defined name.
The SingleReference::Sheet member shall contain
the index of the external sheet cache containing the values of the
externally referenced cells.
