One identifier (such as a DOI, URN, standard designator, or standards organization’s internal document ID) for a standard, using the @std-relationship-type attribute to name the type of identifier (such as dated or undated designations).
Several <std-id> identifiers may be grouped into a container element <std-id-group> to indicate that they are alternative identifiers for the same standard. For example, such a group could contain: one <std-id> containing a DOI, a second <std-id> containing a URN, and a third containing a standards-producing organization’s internal-processing identifier. Thus each <std-id> (with its attributes) can be used inside the <std-id-group> element to support the coupling of identifiers, such as the designator and the URN, and to describe this relationship.
Text, numbers, or special characters, zero or more
... <std ><std-ref>ISO 9001:2015</std-ref> <std-id-group> <std-id std-id-type="dated" std-id-link-type="doi" originator="ISO">10.9999/ISO-9001:2015</std-id> <std-id std-id-type="dated" std-id-link-type="doi" std-relationship-type="std-adopted-from" originator="EN">10.9998/EN-ISO-9001:2015</std-id> <std-id std-id-type="dated" std-id-link-type="doi" std-relationship-type="std-adopted-from" originator="BSI" >10.9998/BS-EN-ISO-9001:2015</std-id> </std-id-group></std> ...