W3C home > Mailing lists > Public > semantic-web@w3.org > February 2011

Re: How to write a UNION in SPARQL.

From: Olivier Rossel <datao@datao.net>
Date: Wed, 16 Feb 2011 10:52:48 +0100
Message-ID: <AANLkTimfFMkJWoqPQf1-zHycAHHGq+hhbuqhgR6oyqTG@mail.gmail.com>
To: Semantic Web <semantic-web@w3.org>
On Wed, Feb 16, 2011 at 10:49 AM, Olivier Rossel <datao@datao.net> wrote:
> In DBPedia, I want to get a list of presidents born in 1945.
> A president is either a "onto:President" or a "yago:President".
> So a UNION is needed to manage both.
>
> One way to write the corresponding SPARQL query is :
>
> PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
> PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
> PREFIX onto: <http://dbpedia.org/ontology/>
> PREFIX yago: <http://dbpedia.org/class/yago/>
> SELECT DISTINCT ?uri ?string
> WHERE
> {
>        {
>                ?uri rdf:type onto:President .
>                ?uri onto:birthDate ?date .
>                FILTER regex(?date, "^1945") .
>                OPTIONAL {?uri rdfs:label ?string .}
>                FILTER (lang(?string) = "en")
>        }
>        UNION
>        {
>                ?uri rdf:type yago:President.
>                ?uri onto:birthDate ?date .
>                FILTER regex(?date, "^1945") .
>                OPTIONAL {?uri rdfs:label ?string .}
>                FILTER (lang(?string) = "en")
>        }
> }
>
> Another way is :
>
> PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
> PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
> PREFIX onto: <http://dbpedia.org/ontology/>
> PREFIX yago: <http://dbpedia.org/class/yago/>
> SELECT DISTINCT ?uri ?string
> WHERE
> {
>        {{
>                ?uri rdf:type onto:President .
>
>        }
>        UNION
>        {
>                ?uri rdf:type yago:President.
>
>        }}.
>       ?uri onto:birthDate ?date .
>                FILTER regex(?date, "^1945") .
>                OPTIONAL {?uri rdfs:label ?string .}
>                FILTER (lang(?string) = "en")
> }
>

(Oops, I sent the mail a bit too fast :)
So:
Which syntax is considered to be optimal?
Are there some best practices when using UNIONs?

Any help is welcome.

Olivier Rossel
--
Datao.net
Received on Wednesday, 16 February 2011 09:53:20 GMT

This archive was generated by hypermail 2.3.1 : Tuesday, 26 March 2013 21:45:41 GMT