"or" in a SPARQL query

Question

I don't quite understand why in SPARQL they haven't implemented the basic logic operators. However in most of the cases is possible to obtain the same result in a number of way.

The purpose of this question is to have a quick reference for the possible way troughs that can substitute an "or" statement.

Here's what I can think of:

1)UNION

e.g:

SELECT * WHERE {  { ?s :propA ?o } UNION { ?s :propB ?o }  } 

-not often suitable because it can became very verbose because

SELECT * WHERE {      { GRAPH ?g {?s ?p ?o. ?o ?pp ?data1}} UNION      { GRAPH ?g {?s ?p ?o. ?o ?pp ?data2}} }  

doesn't work as

SELECT * WHERE {      GRAPH ?g {        ?s ?p ?o.         {?o ?pp ?data1} UNION         {?o ?pp ?data2}      }  } 

(at least not with Stardog)

2)FILTER

e.g:

SELECT * WHERE     {          ?s ?p ?o.         FILTER (?p = :propA || ?p = :propB )     } 

Any other ideas?

Answer 1

I'm not entirely sure why you say SPARQL doesn't supply 'the basic logic operators', because your own examples clearly show that it does: it provides logical-OR (||) and logical-AND (&&) as part of FILTER conditions, and disjunctive graph patterns using UNION (of course, conjunctive graph patterns need no special syntax).

Other variations of OR-like constructs are also possible. For queries of the form "this particular value must be one of these possibilities" you can use the set membership operator, IN:

SELECT *  WHERE {      ?s ?p ?o.     FILTER (?p IN (:propA, :propB, :propC ) ) } 

You can also use the VALUES clause for this kind of pattern:

SELECT *  WHERE {     VALUES ?p { :propA :propB :propC }      ?s ?p ?o. } 

Update I forgot one, perhaps the simplest. For queries such as yours, where you are looking for a few alternatives for a property name, you can actually use a property path expression as well, like so:

SELECT *  WHERE {     ?s :propA|:propB|:propC ?o. } 

Answer 2

If you want to trace which predicate lead to which object then this is universal solution for "OR" :

SELECT DISTINCT ?s ?o1 ?o2  WHERE {   {      ?s p1 ?o1 .      OPTIONAL      {         ?s p2 ?o2 .      }   }    UNION    {      ?s p2 ?o2 .      OPTIONAL      {         ?s p1 ?o1 .      }   } }