In this data structure, what is the XML terminology for the currency= " usd "...

In this data structure, what is the XML terminology for the currency= " usd " code snippet?

< ? xml version= " 1.0 " encoding= " UTF-8 " ? >

< ciscopress >

< book isbn= " 50581730795252386 " >

< title > Routing TCP/IP < /title >

< author > Jeff Doyle < /author >

< category > < /category >

< year > 2005 < /year >

< edition > 2 < /edition >

< price currency= " usd " > 72 < /price >

< /book >

< /ciscopress >