The SELECT statement of a query can include expressions, not just variables.
This involves is a syntactic extension and is available if the query is
parsed with language Syntax.syntaxARQ.
Expressions are enclosed in () and can be optionally named using
AS. If no name is given, and internal name is allocated which may
not be a legal SPARQL variable name. In order to make results portable in the
SPARQL Query Results XML
Format, the application must specify the name so using AS is
strongly encouraged.
Expressions can involve group aggregations.
Expressions that do not correctly evaluate result in an unbound variable in the results. That is, the illegal expression is silently skipped.
Examples:
PREFIX : <http://example/>
SELECT (?p+1 AS ?q)
{
:x :p ?p
}
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
PREFIX : <http://example/>
SELECT (count(*) AS ?count)
{
:x rdf:type :Class
}