Recommended practice is to use a controlled vocabulary where available. For example, for file formats one could use the list of Internet Media Types [[MIME](https://www.iana.org/assignments/media-types/media-types.xhtml)]. (en)
A [second property](/specifications/dublin-core/dcmi-terms/#http://purl.org/dc/terms/format) with the same name as this property has been declared in the [dcterms: namespace](http://purl.org/dc/terms/). See the Introduction to the document [DCMI Metadata Terms](/specifications/dublin-core/dcmi-terms/) for an explanation. (en)