In ISO STS, this attribute named the designator for the standard being cited (in the element <std>). Current NISO STS Best Practice does not use this attribute; rather the identifier for a standard being cited should be tagged either

• in a <std-id> element (for a single identifier, equivalent to this attribute) or, more typically,

• using the element <std-id-group> which holds several standard identifiers (<std-id>), for example, both a dated and an undated designator.