簡潔な答え
簡単に言えば、クエリが構文的に適切に形成されておらず、探しているものが返されないということです。.クエリは、セミコロン ( ) ではなくピリオド ( )でトリプル パターンを終了する必要があります;。固定クエリは次のようになります。
PREFIX schema: <http://schema.org/>
SELECT ?description
WHERE {
?review a schema:Review ;
schema:author "Judson C." .
}
ただし、これはクエリで使用されないSELECT変数?descriptionであるため、常に空です。おそらくSELECT ?review、パターンに追加するか、パターンに追加しますschema:description ?description。
長い答え
これが機能することを示すもう少し詳細が続きます。あなたが提供した RDF は整形式ではないため、それに対してテストするのは困難です。私はあなたが提供したものを取り、それをN3として書き、次のようにしました. (RDF/XML も回答の最後にあります。)
@prefix schema: <http://schema.org/> .
[]
a schema:Rating ;
schema:ratingValue "5.0" .
[]
a schema:Review ;
schema:reviewRating [] ;
schema:description "OMG Love this place!! But glad I don't have to stand in line for an hour like back in the day to get my fix!" ;
schema:datePublished "2013-05-18" ;
schema:author "Judson C." .
[]
a schema:Review ;
schema:reviewRating [] ;
schema:description "If you're ever wondering of where to stuff your face with a good ol' sandwich, you'll definitely have to pop in at Ike's Place. Not only are the different sandwiches uniquely named, they're also uniquely flavor profiled. A wonderful experience indeed!Sandwiches I've personally ordered are the Love Triangle, Nacho girl, and the Al Bundy. For all you people out there who loved the tv show, Married with Children, I think you could appreciate the sentiment of having a sammie named after the 'No Ma'am enthusiast. I know I did. Ahhh... *tucks hand under pant waistband*All kidding aside, these sandwiches are pretty legit. You go to the counter and order whichever sandwich sounds appealing and they can either add chips or a drink to your meal. Simple. They have a wide range of sandwiches that are made to please any meat lover, vegetarian, or vegan palate alike. The huge variety is an A+ in my book. They can even individualize and customize your sandwich to your liking. This means that even the pickiest of eaters are welcome!So if you're interested in a fun place to enjoy a good sandwich, most definitely give 'em a try!" ;
schema:datePublished "2013-04-30" ;
schema:author "Ann S." .
前述のように、クエリにはいくつかの構文エラーがあります。トリプル パターンは.ではなく で終わる必要があり、次の;ようにする必要があります。
PREFIX schema: <http://schema.org/>
SELECT ?description
WHERE {
?review a schema:Review ;
schema:author "Judson C." .
}
?descriptionただし、クエリで使用されていないため、これは有用なものを返しません。Jena の ARQ を使用して (およびクエリを schema.query として記述)、1 つの行 (パターンが一致したため) を出力しますが、バインドされていない変数を使用します。
$ /usr/local/lib/apache-jena-2.10.0/bin/arq \
--query schema.query \
--data schema.n3
---------------
| description |
===============
| |
---------------
バインドするクエリは次の?descriptionとおりです。
PREFIX schema: <http://schema.org/>
SELECT ?description
WHERE {
?review a schema:Review ;
schema:author "Judson C." ;
schema:description ?description .
}
予想どおり、いくつかの有用な結果が得られます。
$ /usr/local/lib/apache-jena-2.10.0/bin/arq \
--query schema2.query \
--data schema.n3
-------------------------------------------------------------------------------------------------------------------
| description |
===================================================================================================================
| "OMG Love this place!! But glad I don't have to stand in line for an hour like back in the day to get my fix!" |
-------------------------------------------------------------------------------------------------------------------
RDF/XML 付録
手元にあるデータの RDF/XML シリアル化は次のとおりです。
<rdf:RDF
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
xmlns:schema="http://schema.org/">
<schema:Review>
<schema:reviewRating rdf:parseType="Resource">
</schema:reviewRating>
<schema:description>If you're ever wondering of where to stuff your face with a good ol' sandwich, you'll definitely have to pop in at Ike's Place. Not only are the different sandwiches uniquely named, they're also uniquely flavor profiled. A wonderful experience indeed!Sandwiches I've personally ordered are the Love Triangle, Nacho girl, and the Al Bundy. For all you people out there who loved the tv show, Married with Children, I think you could appreciate the sentiment of having a sammie named after the 'No Ma'am enthusiast. I know I did. Ahhh... *tucks hand under pant waistband*All kidding aside, these sandwiches are pretty legit. You go to the counter and order whichever sandwich sounds appealing and they can either add chips or a drink to your meal. Simple. They have a wide range of sandwiches that are made to please any meat lover, vegetarian, or vegan palate alike. The huge variety is an A+ in my book. They can even individualize and customize your sandwich to your liking. This means that even the pickiest of eaters are welcome!So if you're interested in a fun place to enjoy a good sandwich, most definitely give 'em a try!</schema:description>
<schema:datePublished>2013-04-30</schema:datePublished>
<schema:author>Ann S.</schema:author>
</schema:Review>
<schema:Review>
<schema:reviewRating rdf:parseType="Resource">
</schema:reviewRating>
<schema:description>OMG Love this place!! But glad I don't have to stand in line for an hour like back in the day to get my fix!</schema:description>
<schema:datePublished>2013-05-18</schema:datePublished>
<schema:author>Judson C.</schema:author>
</schema:Review>
<schema:Rating>
<schema:ratingValue>5.0</schema:ratingValue>
</schema:Rating>
</rdf:RDF>