Thank you, Andy, for a detailed description. I am interested in learning more
about SPARQL from you, can you link me to some of your video lectures which I
can watch to learn basics? It would be helpful.
Regards,
Samita Bai
________________________________
From: Andy Seaborne <a...@apache.org>
Sent: 26 March 2021 15:32
To: users@jena.apache.org <users@jena.apache.org>
Subject: Re: About Parameterized SPARQL String
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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