- From: Adrian Walker <adriandwalker@gmail.com>
- Date: Fri, 5 Jun 2009 13:24:40 -0400
- To: Lee Feigenbaum <lee@thefigtrees.net>, ding@cs.byu.edu, jitao.yang@gmail.com
- Cc: public-sparql-dev@w3.org
- Message-ID: <1e89d6a40906051024q4363c54cx8b7e7dd1be3eba65@mail.gmail.com>
Jitao, Lee, & All --
You may be interested in the approach to querying RDF in
www.reengineeringllc.com/demo_agents/RDFQueryLangComparison1.agent
An advantage would appear to be that it is clearer what question is actually
being asked.
BTW, does anyone know please of a reasonably stable SPARQL implementation
that exposes a lower level API than SPARQL itself?
Cheers, -- Adrian
On Fri, Jun 5, 2009 at 12:35 PM, Lee Feigenbaum <lee@thefigtrees.net> wrote:
> Jitao Yang wrote:
>
>> Another problem is:
>> if I add another new book which has no authors to the RDF file like:
>>
>> <?xml version="1.0" encoding="utf-8"?>
>> <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
>> xmlns:dc="http://purl.org/dc/elements/1.1/"
>> xmlns:vcard="http://www.w3.org/2001/vcard-rdf/3.0#">
>> <rdf:Description rdf:about="http://example.org/BookJava">
>> <vcard:fullname>Book Java</vcard:fullname>
>> <dc:author>
>> <rdf:Description rdf:about="
>> http://example.org/BookJava/authorA">
>> <dc:fullname>Bob Smith</dc:fullname>
>> <dc:country>Italy</dc:country>
>> </rdf:Description>
>> </dc:author> <dc:author>
>> <rdf:Description rdf:about="
>> http://example.org/BookJava/authorB">
>> <dc:fullname>Tom Bush</dc:fullname>
>> <dc:country>Italy</dc:country>
>> </rdf:Description>
>> </dc:author>
>> </rdf:Description>
>>
>> <rdf:Description rdf:about="http://example.org/BookCpp">
>> <vcard:fullname>Book Cpp</vcard:fullname>
>> <dc:author>
>> <rdf:Description rdf:about="http://example.org/BookCpp/author2
>> ">
>> <dc:fullname>Mike Luck</dc:fullname>
>> <dc:country>France</dc:country>
>> </rdf:Description>
>> </dc:author>
>> <dc:author>
>> <rdf:Description rdf:about="http://example.org/BookCpp/author1
>> ">
>> <dc:fullname>Alice Bird</dc:fullname>
>> <dc:country>Italy</dc:country>
>> </rdf:Description>
>> </dc:author> <dc:author>
>> <rdf:Description rdf:about="
>> http://example.org/BookJava/authorB">
>> <dc:fullname>kobe Mc</dc:fullname>
>> <dc:country>Italy</dc:country>
>> </rdf:Description>
>> </dc:author>
>> </rdf:Description>
>>
>> <rdf:Description rdf:about="http://example.org/BookC">
>> <vcard:fullname>Book C</vcard:fullname>
>> </rdf:Description>
>>
>> </rdf:RDF>
>>
>> I want to query "the books whose authors are all Italian" or "the books
>> which have no authors",
>> so I use SPARQL like:
>>
>> PREFIX dc:<http://purl.org/dc/elements/1.1/>
>> PREFIX vcard:<http://www.w3.org/2001/vcard-rdf/3.0#>
>> SELECT DISTINCT ?bookName
>> WHERE {
>> ?bookURI vcard:fullname ?bookName .
>> OPTIONAL{
>> ?bookURI dc:author ?author .
>> ?author dc:country ?country .
>> FILTER(?country = \"Italy\") .
>> OPTIONAL{
>> ?bookURI dc:author ?author2 .
>> ?author2 dc:country ?country2 .
>> FILTER(?country2 != \"Italy\")
>> }
>> FILTER(bound(?country2))
>> }
>> FILTER(!bound(?author))
>> }
>>
>> I can get the right answers:
>> ---------------
>> | bookName |
>> ===============
>> | "Book C" |
>> | "Book Java" |
>> ---------------
>> but, my original idea is FILTER(!bound(?country2)) which means filter the
>> books which have non-Italian authors,
>> however if I use FILTER(!bound(?country2)), it will return the opposite
>> answers:
>> --------------
>> | bookName |
>> ==============
>> | "Book C" |
>> | "Book Cpp" |
>> --------------
>> I can not understand the reasons?
>>
>> Thank you very much if Lee would like to explain to me,
>> or the other persons who have time to help me?
>>
>
> Because of the !bound(?author), you're only going to receive books that
> don't satisfy your outer optional. Because the outer optional requires an
> author, this will include books with no author, as you want.
>
> Books with an author will only satisfy the outer optional if
> bound(?country2) is true, which is true only if the book has a non-Italian
> author. So you end up excluding those as well, as you want.
>
> That said, I think you've made the query overly complicated. Would this
> accomplish what you want?
>
> PREFIX dc:<http://purl.org/dc/elements/1.1/>
> PREFIX vcard:<http://www.w3.org/2001/vcard-rdf/3.0#>
> SELECT DISTINCT ?bookName
> WHERE {
> ?bookURI vcard:fullname ?bookName .
> OPTIONAL{
> ?bookURI dc:author ?author .
> ?author dc:country ?country .
> FILTER(?country != "Italy") .
> }
> FILTER(!bound(?author))
> }
>
> (This is simply the original query but with the part that required at least
> one Italian author removed.)
>
>
> Lee
>
> Best wishes,
>> Jitao
>>
>>
>> On Sat, May 30, 2009 at 21:51, Lee Feigenbaum <lee@thefigtrees.net<mailto:
>> lee@thefigtrees.net>> wrote:
>>
>> Jitao Yang wrote:
>>
>> Dear all,
>>
>> if there is a RDF like:
>>
>> <?xml version="1.0" encoding="utf-8"?>
>> <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
>> xmlns:dc="http://purl.org/dc/elements/1.1/">
>> <rdf:Description rdf:about="http://example.org/BookJava">
>> <dc:fullname>Book Java</dc:fullname>
>> <dc:author>
>> <rdf:Description
>> rdf:about="http://example.org/BookJava/authorA">
>> <dc:fullname>Bob Smith</dc:fullname>
>> <dc:country>Italy</dc:country>
>> </rdf:Description>
>> </dc:author> <dc:author>
>> <rdf:Description
>> rdf:about="http://example.org/BookJava/authorB">
>> <dc:fullname>Tom Bush</dc:fullname>
>> <dc:country>Italy</dc:country>
>> </rdf:Description>
>> </dc:author>
>> </rdf:Description>
>>
>> <rdf:Description rdf:about="http://example.org/BookCpp">
>> <dc:fullname>Book Cpp</dc:fullname>
>> <dc:author>
>> <rdf:Description
>> rdf:about="http://example.org/BookCpp/author1">
>> <dc:fullname>Alice Bird</dc:fullname>
>> <dc:country>Italy</dc:country>
>> </rdf:Description>
>> </dc:author> <dc:author>
>> <rdf:Description
>> rdf:about="http://example.org/BookCpp/author2">
>> <dc:fullname>Mike Luck</dc:fullname>
>> <dc:country>France</dc:country>
>> </rdf:Description>
>> </dc:author>
>> </rdf:Description>
>> </rdf:RDF>
>>
>>
>> and I query the RDF by:
>>
>> PREFIX dc:<http://purl.org/dc/elements/1.1/>
>> SELECT DISTINCT ?bookName
>> WHERE {
>> ?bookName dc:author ?author .
>> {?author dc:country ?country . FILTER(?country
>> = "Italy")}
>> };
>>
>> the query results are:
>>
>> ---------------------------------
>> | bookName |
>> =================================
>> | <http://example.org/BookCpp> |
>> | <http://example.org/BookJava> |
>> ---------------------------------
>>
>> can anybody tell me how to query out the "book whose authors'
>> country are all Italy "?
>>
>
>
>
>
> which means the query results should be:
>>
>> ---------------------------------
>> | bookName |
>> =================================
>> | <http://example.org/BookJava> |
>> ---------------------------------
>>
>>
>> Jitao,
>>
>> It's not pretty, but you should be able to do it with something like:
>>
>> PREFIX dc:<http://purl.org/dc/elements/1.1/>
>> SELECT DISTINCT ?bookName
>> WHERE {
>> # first, make sure there's an author from italy
>> ?bookName dc:author ?author .
>>
>> ?author dc:country ?country . FILTER(?country = "Italy") .
>> # next, "try" to find another author not from italy
>> OPTIONAL {
>> ?bookName dc:author ?author2 .
>> ?author2 dc:country ?country2 .
>> FILTER(?country2 != "Italy")
>> }
>> # finally, we only want this book if we didn't find any non-Italy
>> # authors
>> FILTER(!bound(?country2))
>> }
>>
>> (Warning, untested query.)
>>
>> hope this helps,
>> Lee
>>
>>
>>
>> Thank you very much for your help!
>>
>> Best wishes,
>> Jitao
>>
>>
>>
>>
>
Received on Friday, 5 June 2009 17:25:22 UTC