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Querying the Semantic Web-SPARQL
A TEAM
오혜성, 조형헌, 권윤, 신동준, 이인용
contents
 What is SPARQL
 Tell and Ask system.
 Development of Relational DB
 RDF and SPARQL
 Use of SPARQL
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What is SPARQL
SPARQL
Protocol
and
RDF Query Language
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What is SPARQL
1. W3C에 의해 2008년에 개발된
2. RDF 형식으로 정보가 저장된 DB에 대해
3. SPARQL endpoint를 통해
4. 검색, 조작 등의 명령을 내릴 수 있는
5. Query Language
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Advantages of SPARQL
1. subject-predicate-object 의 쿼리 뿐만
아니라 key-value형식 쿼리도 가능하다.
2.쿼리만이 아니라 새로운 RDF를 구성할 수도 있다.
3.그래프패턴의 질의가 가능하다.
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Tell and Ask system
• TELL operation
:어떠한 fact에 대해 말해준다.
(Axioms, TBox, ABox, the ontology)
• Ask operation
:그로부터 infer 할 수 있는 것을 요청한다.
(Answer = boolean or Non-boolean)
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Spreadsheet
• 가장 기본적 Tell-Ask 인프라 구조
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Spreadsheet
• When we get this situation…
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Spreadsheet
• When we get this situation…
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Spreadsheet
• How About this?
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Spreadsheet
• How About this?
This is workable, but begins to degrade the main advantages of spreadsheet
We can no longer use visualization to answer questions
Relies of cross-references that are not readily visible by examining the
spreadsheet
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We need new system!
• Advanced tell-and-ask infrastructure
It should be more Structured form!!
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The answer is Relational DB
It provides a systematic way to link tables together!!
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Relational Database
• What change in it?
→Represent highly structured data.
→Respond to very detailed, structured questions
So asking a question becomes a very detailed process
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RDF as a Tell-and-Ask System
• Also like a relational database, RDF requires a precise query
language to specify questions
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RDF as a Tell-and-Ask System
• All of these questions can be asked in SPARQL
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RDF as a Tell-and-Ask System
• All of these questions can be asked in SPARQL
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Make it Query Language
• It looks like some structure…
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It can be done with “SELECT”
• SELECT lists of the question words we are interested in
• WHERE indicates the selection pattern, written in braces
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WHERE
• WHERE clause can be seen as a graph pattern
• Query engine finds all matches for the pattern in the data,
and returns all the values that the question word matched
• Query can specify a graph pattern with more than one
triples
• Since the variable ?what appears in both triples, the graph
pattern is joined
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Naming question words
• English Question word
->who what where when whom etc
• In SPARQL…
-> Anything you want! Just Put [?]
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In easy way
• We can make the table by selecting descriptive
question words
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Query structure vs data structure
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Ordering of triples in SPARQL queries
• The order makes no difference to an RDF data graph
• However, execution time could be affected by the
order
• Tip! : Order triples in a query so that the fewest number of new variables
are introduced in each new triple
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Other querying
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Other querying
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Other querying
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Other querying (1.1ver)
• Negation could be useful
• [UNSAID] : Introduces a subgraph; the overall graph pattern will
match just if the UNSAID pattern does not match
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Other querying
• ASK
쿼리의 TRUE/FALSE 만을 return
• CONSTRUCT
DB에서 뽑은 정보를 정규RDF형식에 맞춤
• DESCRIBE
결과를 RDF 그래프로 출력
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Advanced Features of SPARQL
• ORDER BY : 정렬순서를 속성순으로
• LIMIT : 개수 제한
• 그외 여러가지 기능
(COUNT, MIN, MAX, AVG, and SUM )
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Advanced Features of SPARQL
• GROUP BY: 위의 명령어와 조합하여 그룹
별 개수, 최소 ,최대등을 구할수있다.
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Advanced Features of SPARQL
• HAVING: 특정 조건을 만족하는 결과만 보여준다.
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Advanced Features of SPARQL
• UNION: OR와 같다고 볼 수 있다. 각 조건을 만족
하는 결과들을 함께 return 한다.
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Federating SPARQL Queries
• We assumed that all the data triples were available in a
single graph = real?
• SPARQL can federate a query across more than one
data source
• Data sources on the Web can participate in federated
query through SPARQL endpoints
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Example of Federating
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Summary
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