OptionalabsoluteAbsolute URL to the external resource (e.g. a OneDrive web URL).
OptionaldriveOneDrive/SharePoint drive identifier Excel writes alongside cloud alternate URLs. Used by Microsoft Graph API calls to locate the container holding the external document, independent of the URL. Opaque string; round-tripped verbatim.
OptionalitemOneDrive/SharePoint item identifier — the resource-level counterpart
to driveId; used by Microsoft Graph API calls to locate the external
document itself. Opaque string; round-tripped verbatim.
OptionalrelativeRelative URL to the external resource.
Alternate URLs for an external workbook — typically used when the source file lives in a cloud location (OneDrive, SharePoint). In XLSX, this corresponds to the
<alternateUrls>extension element inside<externalBook>(from the 2021 extlinks2021 namespace).absoluteUrl/relativeUrlare captured from child elements of<alternateUrls>;driveId/itemIdare attributes on the<alternateUrls>element itself.At least one subfield must be set for the value to be meaningful; a purely empty
{}is allowed by the type but producers and consumers should omit it in that case. Each subfield is independently optional per the extlinks2021 schema.