SPARQL

Hello,

my name is Andr�� Bolles and I'm studying computer science in Oldenburg,
Germany. In the context of my diploma thesis I analysed the technical
report:

SPARQL Query Language for RDF

By doing this I think found some unclear parts in this document, so that
there may be some users who do not exactly know how to evaluate some
queries. I will tell you these parts and explain why I think these parts are
not clear.

1.
In the left join definition there is said the following:

LeftJoin(��1, ��2, expr) =
    { merge(��1, ��2) | ��1 in ��1and ��2 in ��2, and ��1 and ��2 are
compatible and expr(merge(��1, ��2)) is true } set-union
    { ��1 | ��1 in ��1and ��2 in ��2, and ��1 and ��2 are not compatible }
set-union
    { ��1 | ��1 in ��1and ��2 in ��2, and ��1 and ��2 are compatible and
expr(merge(��1, ��2)) is false }


But, what if there is no solution in ��2. The sparql implementation in ARQ
says that in this case the solution from ��1 will be taken, but this is not
said in the technical report.

2. There is said:

A solution mapping, ��, is a partial function �� : V -> T.

But what is T. I think you mean RDF-T.

3. The ___domain of ��, dom(��), is the subset of V where �� is defined.

This is trivial, because dom(x) always defines the set, where x is defined.
This is the definition of dom.

Maybe these hints can be helpful by improving this recommendation.

Greetings,

Andre Bolles

Received on Friday, 18 January 2008 18:11:43 UTC