Hi Samita,
The values are inserted in to the overall query at the point where they
are bound. There are 3 places allowed - Basic Graph Pattern Matching
Property Path Patterns and GRAPH ?g - which are the places where SPARQL
touches the data.
Let;'s say we have { ?s ?p ?o } and we want ?s to be ex:s.
this becomes (written in SPARQL syntax)
{ ?s ?p ?o VALUES ?s { ex:s } }
which is join( {?s ?p ?o }, T) where T is the table from VALUES.
{ ?s :p ?o } UNION { ?s :q ?z }
becomes
{ ?s ?p ?o VALUES ?s { ex:s } } UNION { ?s :q ?z VALUES ?s { ex:s } }
multiple joins -- the algebra forms are given in the write-up.
Doing it this way leaves the variable in-place, so it can be used in
expressions but the value it has is forced to a specific RDF term.
Andy
On 25/03/2021 16:52, Samita Bai / PhD CS Scholar @ City Campus wrote:
Dear Andy,
I read about the EXISTS from the link you sent. I can now understand your
answer partially, can you please elaborate the following statement more.
The pattern is rewritten to inject a "join" into each place the
variables can become bound. It is not a single join.
It would be helpful.
Thanks in advance for your consideration.
Regards,
Samita Bai
________________________________
From: Andy Seaborne <a...@apache.org>
Sent: 25 March 2021 17:57
To: users@jena.apache.org <users@jena.apache.org>
Subject: Re: About Parameterized SPARQL String
https://afs.github.io/substitute
This covers use in EXISTS but the mechanism is general and gives a
foundation for value-substitution.
Is it "join" - yes and no.
The pattern is rewritten to inject a "join" into each place the
variables can become bound. It is not a single join.
Andy
On 25/03/2021 09:05, Rob Vesse wrote:
ParameterizedSparqlString works by simple textual substitution into the
provided query string so you get a more specific query with your parameters
It does not have any relationship to joins.
I guess what you may be asking is how it compares to other methods for
providing initial bindings e.g. adding VALUES to a query which would be
evaluated as a Join? The answer there is that it isn't really a fair
comparison, a parameterized query vs one using VALUES might yield very
different query execution plans so perform very differently. As with all
queries it's going to depend on both your queries and your data
Rob
On 25/03/2021, 08:31, "Samita Bai / PhD CS Scholar @ City Campus"
<s...@iba.edu.pk> wrote:
Hello everyone,
I have used Parameterized SPARQL String for providing initial solution
bindings for query execution. I need to document my technique; can anyone help
me how can we compare Parameterized SPARQL String with joins?
Is Parameterized SPARQL string type of join or its entirely different?
Please someone help me out.
Regards,
Samita Bai
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