Power (exponentiation) and other math function support in SPARQL

Question

I am trying to write a SPARQL query where I want to filter on the square of something, but I am simply unable to figure out how to square a number (x²) (except by multiplying it with itself, of course). I guessed a square root function called math:sqrt() which works, yet nothing like math:pow seems to exist.

How do I get the square of something in SPARQL and, more importantly, where can I read about it and other math functions such as math:sqrt in SPARQL?

Note: This is related to my previous question: Reverse wikipedia geotagging lookup .

score 3 · Answer 1 · answered Sep 10 '09 at 10:07

3

SPARQL supports some XPath arithmetic functions such as + - * /. They are described in the SPARQL spec.

The power function is not supported by the spec. And in any case x*x is more efficient way to compute squares than pow(x,2) would be.

answered Sep 10 '09 at 10:07

laalto

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Hi. Thanks. What about specification of other math functions, such as the square root (math:sqrt seems to work fine) and the trigonometric functions sin, and cos? I updated the question a bit. – Bjarke Freund-Hansen Sep 10 '09 at 11:25
Those would be implementation-specific extensions, not part of the core SPARQL. – laalto Sep 11 '09 at 08:46
Where would I find documentation on these implementation-specific extensions? – Bjarke Freund-Hansen Sep 12 '09 at 08:48
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Well, start with your SPARQL query engine documentation. I cannot read your mind and don't know which one you are using. – laalto Sep 13 '09 at 11:50

score 3 · Accepted Answer · edited May 23 '17 at 11:55

It's now a few years later and the SPARQL 1.1 Query Language has been published. It includes many more built-in functions than the original SPARQL query language. In addition to lots of functions on strings, RDF terms, &c., there are a number of numeric functions (the section numbers indicate the section in the linked standard):

17.4.4 Functions on Numerics

17.4.4.1 abs

17.4.4.2 round

17.4.4.3 ceil

17.4.4.4 floor

17.4.4.5 RAND

There's still no square function here, and the quickest way to implement that will be using *, so laalto's answer still stands. The operators that SPARQL supports are described in 17.3 Operator Mapping, and for XPath arithmetic is still just the set of +, -, *, and /.

Power (exponentiation) and other math function support in SPARQL

2 Answers2

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