Working with language tags

Getting a language tag from a literal

Literals in RDF may be language tagged strings. These literals have a text part as well as a language tag. For instance, the literal “color”@en has the text part “color” and the language tag “en”. In a SPARQL query, use the lang function to get the language of a literal with a language tag. If a literal does not have a language tag, then lang returns the empty string, "".

Comparing language tags

The SPARQL function langMatches can be used to compare the language tags of RDF literals in SPARQL queries. The simple equality operator, =, can be used to compare exact string matches, but will not correctly consider regional variants. For instance, the four possible values of ?str in:

values ?str { "color"@en-US "color"@en "colour"@en "colour"@en-GB }

are all English language strings, but two of these have regional specifications. This means that

select ?str { 
  values ?str { "color"@en-US "color"@en "colour"@en "colour"@en-GB }
  filter (lang(?str) = 'en')
}

will return only two results, since only two of the values of ?str have “en” as a language tag. However,

select ?str { 
  values ?str { "color"@en-US "color"@en "colour"@en "colour"@en-GB }
  filter langMatches(lang(?str), 'en')
}

will return all four values.