[semantic-web] <none>

Hello ,]I'm a tiro on studying in Sparql 1.1 which is the standard language
of RDF. In my survey ,we can do some join like
equal-join,left-outer-join,because the sparql can support the operator
equality ,as well as inequality. However,it also support the operator like
greater or less.So my question is that can we use the operator of greater
or less in the sparql query between two variables, namely,theta-join. I
 saw some research claimed that they do the thetajoin on large graph on the
cloud,but I did't see some sparql queries contained theta-join， neither in
the sparql1.1. So,can you give me some explain what's the problem and can
we use thetajoin like the following examples.
select ?ename ?grade where {
?emp rdf:type f:emp;
foaf:surname ?ename;
f:Sal ?sal.
?salgrade rdf:type f:salgrade;
f:LoSal ?low;
f:HiSal ?high;
f:Grade ?grade.
FILTER (?sal >= ?low && ?sal <= ?high)
}
Looking forward to your reply,thank you .