att.sortable provides attributes for elements in lists or groups that are sortable, but whose sorting key cannot be derived mechanically from the element content. [9.1 Dictionary Body and Overall Structure]
Moduletei — The TEI Infrastructure
Membersbibl biblFull biblStruct correspAction entry entryFree event idno item list listApp listBibl listChange listEvent listNym listOrg listPerson listPlace listRelation listWit msDesc nym org person personGrp place relation superEntry term witness
sortKeysupplies the sort key for this element in an index, list or group which contains it.
Status Optional

<rng:ref name="data.word"/>
David's other principal backer, Josiah
ha-Kohen <index indexName="NAMES">
 <term sortKey="Azarya_Josiah_Kohen">Josiah ha-Kohen b. Azarya</term>
</index> b. Azarya, son of one of the last gaons of Sura was David's own first

The sort key is used to determine the sequence and grouping of entries in an index. It provides a sequence of characters which, when sorted with the other values, will produced the desired order; specifics of sort key construction are application-dependent

Dictionary order often differs from the collation sequence of machine-readable character sets; in English-language dictionaries, an entry for 4-H will often appear alphabetized under ‘fourh’, and McCoy may be alphabetized under ‘maccoy’, while A1, A4, and A5 may all appear in numeric order ‘alphabetized’ between ‘a-’ and ‘AA’. The sort key is required if the orthography of the dictionary entry does not suffice to determine its location.