D2R-Q

1
D2R-Q

• Work together with Andy, Chris and Kevin
• Goal Query huge, live, non-RDF data bases with
  RDQL
• Allow access to existing databases
• Allow a more efficient storage of application
  specific RDF data
• Approach
• Develop a declarative mapping language, that
  allows to
• rewrite RDQL and find(spo) queries to application
  specific SQL queries.
• Redesign my D2R MAP language
• Implement it as a Jena graph

2
D2R-Q Architecture
RDFApp
Query Update
Query
App-specificdatabase
Jena extended with D2R-Q Graph
Non-RDFApp
Joseki
Uses
D2R-Q MAP
3
Structure of a D2R-Q MAP
4
Example

• Part of a map about authors, papers and
  conferences

InProceedings rdftype rdfsClass
d2rclassMap db1InProceedings . db1InProceedings
rdftype d2rClassMap d2ruriPattern
"http//www.example.org/ db01Paper_at__at_Papers.PaperI
D_at__at_" d2rdataStorage db1Database1
. title rdftype rdfProperty
d2rpropertyBridge db1inProceedingsTitle
. db1inProceedingsTitle rdftype
d2rDatatypePropertyBridge
d2rcolumn "Papers.Title"
d2rbelongsToClassMap db1InProceedings
d2rdataType dtypestring
. author rdftype rdfProperty
d2rpropertyBridge db1inProceedingsAuthor
. db1inProceedingsAuthor rdftype
d2rObjectPropertyBridge d2rjoin
"Papers.PaperID Rel_Person_Paper.PaperID"
d2rjoin "Rel_Person_Paper.PaperID
Persons.PerID" d2rbelongsToClassM
ap db1InProceedings
d2rrefersToClassMap db1PersonsClassGroupMap
.
5
Example Query find(s p o)

• Find (ANY, iswctitle, RDF in XML)
• Algorithm
• Look at Predicate
• Find ClassMaps
• Get ColumnNames
• Get Tables
• Execute SQL
• Return results
• SQL

InProceedings rdftype rdfsClass d2rclassMap
db1InProceedings . db1InProceedings rdftype
d2rClassMap d2ruriPattern
"http//www.example.org/ db01Paper_at__at_Papers.PaperI
D_at__at_" d2rdataStorage db1Database1 . title
rdftype rdfProperty d2rpropertyBridge
db1inProceedingsTitle . db1inProceedingsTitle
rdftype d2rDatatypePropertyBridge
d2rcolumn "Papers.Title"
d2rbelongsToClassMap db1InProceedings
d2rdataType dtypestring.
SELECT Papers.PaperIDFROM PapersWHERE
Papers.Title RDF in XML
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Example Query find(s p o) with a Many-to-Many Join

• Find(ANY, iswcauthor, http//www.persons.orgP123
  4)
• Algorithm
• Look at Predicate
• Find ClassMaps
• Find ReferedMaps
• Get ColumnNames
• Get Tables
• Execute SQL
• SQL

author rdftype rdfProperty
d2rpropertyBridge db1inProceedingsAuthor
. db1inProceedingsAuthor rdftype
d2rObjectPropertyBridge d2rjoin
"Papers.PaperID Rel_Person_Paper.PaperID"
d2rjoin "Rel_Person_Paper.PaperID
Persons.PerID" d2rbelongsToClassMap
db1InProceedings d2rrefersToClassMap
db1PersonsClassMap .
SELECT Papers.PaperIDFROM Papers, Persons,
Rel_Person_Paper WHERE Papers.PaperID
Rel_Person_Paper.PaperID AND
Rel_Person_Paper.PaperID Persons.PerID
AND Persons. PersonID 1234
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Query Performance find(s p o)

• find (?x p o) OK (I guess)
• find (?x p ?z) OK
• find (s p ?z) OK
• find (s p o) OK
• find (s ?x ?y) slow
• find (?x ?y o) very slow
• find (?x ?y ?z) db dump
• ? Use Pattern groups, because they contain more
  usable information.

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Pattern Groups

• Second step Use Pattern groups because they
  contain more information useable for query
  optimization.
• WHERE part of a RDQL query
• Find all author with papers at "TheConference"
• results in one SQL statement.

(?x iswceventTitle "TheConference") (?y
iswcconference ?x) (?y iswcauthor ?z)
9
D2R-Q Status Quo

• Language designed
• Algorithms designed
• Paper tests with two relatively complex
  ontologies and database schemata (including
  taxonomies and many-to-many relationships).
• Implementation started
• D2RQGraph implements Jena Graph
• D2RQQueryHandler implements Jena QueryHandler.
• D2R-Q will be available under an open source
  license sometime in May.