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Re: query RDF dataset

From: Jitao Yang <jitao.yang@gmail.com>
Date: Mon, 1 Jun 2009 22:37:01 +0200
Message-ID: <eb1226bd0906011337sbad22c7p2ec64a98b6b69583@mail.gmail.com>
To: Lee Feigenbaum <lee@thefigtrees.net>
Cc: public-sparql-dev@w3.org
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?

Best wishes,
Jitao

On Sat, May 30, 2009 at 21:51, Lee Feigenbaum <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 Monday, 1 June 2009 20:37:53 GMT

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