tests around comparators in the graph constraint

On Mon, Dec 13, 2004 at 10:30:35AM -0600, Dan Connolly wrote:
> ACTION: EricP to sketch tests around comparators in the graph
> constraint

Given a graph:

    :book1 dc:title "SPARQL Tutorial" .
    :book1 ns:price 41 .

We can ask for the titles of the books that cost less than $42:

    SELECT ?title
     WHERE (?book dc:title ?title)
           (?book ns:price ?price)
       AND (?price < 42)

or we can use an XQuery (XPath really) function

    SELECT ?title
     WHERE (?book dc:title ?title)
           (?book ns:price ?price)
       AND (?price op:lessThan 42)

Simon suggested we look at expressing that in the WHERE clause:

    SELECT ?title ?price
     WHERE (?book dc:title ?title)
           (?book ns:price ?price)
           (?price op:lessThan 42)

which would presumable match the above data. But would it match

    :book1 dc:title "SPARQL Tutorial" .
    :book1 ns:price :price .
    :price op:lessThan 42.

or

    :book1 dc:title "SPARQL Tutorial" .
    :book1 ns:price 43 .
    43 op:lessThan 42.

? Generally, how do we distinguish between asserted triples and
those inferred? We may want to, especially given that querying a
representation of a query can leave lots of triples in the op
namespace around, potentially confusing or misleading the
querier.

-- 
-eric

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