Graphically Querying RDF Using RDF-GL

Graphically Querying RDF Using RDF-GL

Dutch-Belgian Database Day 2010 (DBDBD 2010)

November 22, 2010

Frederik [email protected]

Viorel [email protected]

Flavius [email protected]

Uzay [email protected]

Erasmus University RotterdamPO Box 1738, NL-3000 DRRotterdam, the Netherlands

This talk is based on the paper RDF-GL: A SPARQL-Based Graphical Query Language for RDF. Hogenboom, F.P., Milea, D.V., Frasincar, F. & Kaymak, U. (2010). In Y. Badr, A. Abraham, A.-E. Hassanien & R. Chbeir (Eds.), Emergent Web Intelligence: Advanced Information Retrieval (Advanced Information and Knowledge Processing) (pp. 87-116). Springer London.

mailto:[email protected]




Introduction

• Increasing amount of information

• Querying large databases quickly and efficiently is desired

• This need is addressed by several tools and languages

• However, intuitiveness is often of less importance (expressivity over clarity)

Dutch-Belgian Database Day 2010 (DBDBD 2010)November 22, 2010

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Graphical Query Languages

• Enable users to create queries by arranging and connecting symbols on a canvas

• Build on existing textual query languages

• Abstract away from difficult syntax and hence aim to enhance intuitiveness

• Coverage of textual equivalents vs. maintaining usability

• Available for semi-structured representations such as XML, but no SPARQL-based GQL for RDF

• RDF-GL is a GQL for a SPARQL subset


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RDF-GL

• Covers most SPARQL SELECT queries

• No support for:– Prologue: BASE and PREFIX– Query type: ASK, CONSTRUCT, DESCRIBE– REDUCED, FROM, NAMED, GRAPH

• However, the design of the language allows for extension

• Based on SPARQL and not on SPARQL 1.1


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RDF-GL: Example (1)


PREFIX j.1: <http://www.daml.org/2003/09/factbook/factbook-ont#>SELECT DISTINCT ?name ?oilWHERE{ ?country j.1:localShortCountryName ?name . ?country j.1:grossDomesticProductPerCapita ?gdp . { FILTER (?gdp < 1500) . } UNION { FILTER (?gdp > 2500) . } OPTIONAL { ?country j.1:oilProvedReserves ?oil . }}ORDER BY ASC(?gdp)

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RDF-GL: Example (2)


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RDF-GL: Basic Elements


{ , }

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RDF-GL: Mapping to SPARQL (1)


PREFIX j.1: <http://www.daml.org/2003/09/factbook/factbook-ont#>SELECT DISTINCT ?elevationWHERE{ ?country j.1:elevation ?elevation .}ORDER BY DESC(?elevation) OFFSET 5 LIMIT 4

Query type andsequence modifiers

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FILTER (?gdp > 1250) .

j.1:EthnicGroup rdfs:subClassOf ?class .

Filters

Triples

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?country j.1:highwaysTotal ?hw .{ FILTER (?hw < 20000) .}UNION{ FILTER (?hw > 150000) .}

Unions

OPTIONAL{ ?country j.1:heliports ?heli .}

Options

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?country j.1:highwaysTotal ?hw .{ FILTER (?hw < 20000) .}UNION{ FILTER (?hw > 150000) . OPTIONAL { ?country j.1:heliports ?heli . }}

Nesting

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RDF-GL: Converting to SPARQL

• Generate default PREFIXes (RDF, RDFS, XSD, etc.)

• Determine query TYPE

• Generate WHERE clause:– Convert all arrows and their connected boxes to triples– Add triples not connected to UNIONs or OPTIONALs to

query– Add UNION and OPTIONAL circles and their children to

query recursively

• Determine ORDER BY

• Determine LIMIT and OFFSET


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Implementation: SPARQLinG (1)


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Implementation: SPARQLinG (2)


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Experiments (1)

• Query the CIA World Factbook for countries which have an import or export to neighbors worth more than $10 billion a year

• The query needs to return:– The names of both the countries and their neighboring

trading partners– The percentages of imports and exports– Optionally the inflation rate of the neighboring partners

• Only the first 20 results are desired and should be ordered by country name (ascending)


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Experiments (2)


PREFIX j.1: <http://www.daml.org/2003/09/factbook/factbook-ont#>SELECT DISTINCT ?nameC ?nameN ?percentExp ?percentImp ?inflationWHERE{ ?country j.1:conventionalShortCountryName ?nameC . ?country j.1:border ?border . ?border j.1:country ?neighbor . ?neighbor j.1:conventionalShortCountryName ?nameN . ?country j.1:exportPartner ?partnerExp . ?partnerExp j.1:percent ?percentExp . ?partnerExp j.1:country ?neighbor . ?country j.1:importPartner ?partnerImp . ?partnerImp j.1:percent ?percentImp . ?partnerImp j.1:country ?neighbor . { ?country j.1:imports ?imports . FILTER (?imports > 10000000000) . } UNION { ?country j.1:exports ?exports . FILTER (?exports > 10000000000) . } OPTIONAL { ?neighbor j.1:inflationRate ?inflation . }}ORDER BY ASC(?nameC) LIMIT 20

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Experiments (3)


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Experiments (4)

• The creation of RDF-GL queries is not necessarily faster than the creation of SPARQL queries

• However, the GQL and tool offer:– Overview– Easy reuse of variables– Maintenance


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Order Dependency in SPARQL

• OPTIONAL is not commutative, causing problems when sharing variables in OPTIONAL clause:

• We need a binary OPTIONAL operator which is commutative and associative


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SELECT ?name ?aliasWHERE{ ?x foaf:name ?name . OPTIONAL { ?x foaf:nick ?alias . } OPTIONAL { ?x foaf:mbox ?alias . }}

SELECT ?name ?aliasWHERE{ ?x foaf:name ?name . OPTIONAL { ?x foaf:mbox ?alias . } OPTIONAL { ?x foaf:nick ?alias . }}

Discussion

• AND-relationship is implicit, OR-relationship is explicit

• Issues:– No coverage for the complete SPARQL language– Determining statement order is difficult

• Solutions:– Extend language by using:

• Extra symbols

• Extra colors/shadings

• Extra shapes

– Add numbers for ordering, make use of the horizontal or vertical position of elements, etc.


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Conclusions

• RDF-GL is a GQL for SPARQL

• The GQL covers a subset of SPARQL (i.e., almost all SELECT queries)

• Future work:– Implement a way to determine query order– Extend the language to include more of SPARQL, i.e., – Visualization:

• Widget size indicating importance• Lay-out algorithm

– SPARQL to RDF-GL conversion


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Questions


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Appendix: EBNF non-terminals (1)


[1] Query ::= SelectQuery[2] SelectQuery ::= ‘SELECT’ ‘DISTINCT’? ( Var+ | ‘*’

) WhereClause SolutionModifier[3] WhereClause ::= ‘WHERE’? GroupGraphPattern[4] SolutionModifier ::= OrderClause? LimitOffsetClauses?[5] LimitOffsetClauses ::= ( LimitClause OffsetClause? |

OffsetClause LimitClause? )[6] OrderClause ::= ‘ORDER’ ‘BY’ OrderCondition+[7] OrderCondition ::= ( ( ‘ASC’| ‘DESC’)

BrackettedExpression ) (Constraint | Var )

[8] LimitClause ::= ‘LIMIT’ INTEGER[9] OffsetClause ::= ‘OFFSET’ INTEGER[10] GroupGraphPattern ::= ‘{’ TriplesBlock?

( ( GraphPatternNotTriples | Filter ) ‘.’? TriplesBlock? )* ‘}’

[11] TriplesBlock ::= TriplesSameSubject ( ‘.’ TriplesBlock? )?

[12] GraphPatternNotTriples ::= OptionalGraphPattern | GroupOrUnionGraphPattern

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Appendix: EBNF non-terminals (2)[13] OptionalGraphPattern ::= ‘OPTIONAL’ GroupGraphPattern[14] GroupOrUnionGraphPatter

n::= GroupGraphPattern ( ‘UNION’

GroupGraphPattern )*[15] Filter ::= ‘FILTER’ Constraint[16] Constraint ::= BrackettedExpression |

BuiltInCall | FunctionCall[17] FunctionCall ::= IRIref ArgList[18] ArgList ::= ( NIL ‘(’ Expression ( ‘,’

Expression )* ‘)’ )[19] TriplesSameSubject ::= VarOrTermPropertyListNotEmpty |

TriplesNode PropertyList[20] PropertyListNotEmpty ::= Verb ObjectList ( ‘;’ ( Verb

ObjectList )? )[21] PropertyList ::= PropertyListNotEmpty?[22] ObjectList ::= Object ( ‘,’ Object )*[23] Object ::= Graphmode[24] Verb ::= VarOrIRIref | ‘a’ [25] TriplesNode ::= Collection |

BlankNodePropertyList[26] BlankNodePropertyList ::= ‘[’ PropertyListNotEmpty ‘]’


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[27] Collection ::= ‘(’ GraphNode+ ‘)’[28] GraphNode ::= VarOrTerm | TriplesNode[29] VarOrTerm ::= Var | GraphTerm[30] VarOrIRIref ::= Var | IRIref[31] Var ::= VAR1[32] GraphTerm ::= IRIref | RDFLiteral |

NumericLiteral | BooleanLiteral | BlankNode | NIL

[33] Expression ::= ConditionalOrExpression[34] ConditionalOrExpression ::= ConditionalAndExpression ( ‘||’

ConditionalAndExpression )*[35] ConditionalAndExpressio

n::= ValueLogical ( ‘&&’

ValueLogical )*[36] ValueLogical ::= RelationalExpression[37] RelationalExpression ::= NumericExpression ( ‘=’

NumericExpression | ‘!=’ NumericExpression | ‘<’ NumericExpression | ‘>’ NumericExpression | ‘<=’ NumericExpression | ‘>=’ NumericExpression )?

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Appendix: EBNF non-terminals (4)[38] NumericExpression ::= AdditiveExpression[39] AdditiveExpression ::= MultiplicativeExpression ( ‘+’

MultiplicativeExpression | ‘-’ MultiplicativeExpression | NumericLiteralPositive | NumericLiteralNegative )*

[40] MultiplicativeExpression

::= UnaryExpression ( ‘*’ UnaryExpression | ‘/’ UnaryExpression )*

[41] UnaryExpression ::= ‘!’ PrimaryExpression | ‘+’ PrimaryExpression | ‘-’ PrimaryExpression | PrimaryExpression

[42] PrimaryExpression ::= BrackettedExpression | BuiltInCall | IRIrefOrFunction | RDFLiteral | NumericLiteral | BooleanLiteral | Var

[43] BrackettedExpression ::= ‘(’ Expression ‘)’


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Appendix: EBNF non-terminals (5)[44] BuiltInCall ::= ‘STR’ ‘(’ Expression ‘)’ | ‘LANG’

‘(’ Expression ‘)’ | ‘LANGMATCHES’ ‘(’ Expression ‘,’ Expression ‘)’ | ‘DATATYPE’ ‘(’ Expression ‘)’ | ‘BOUND’ ‘(’ Var ‘)’ | ‘sameTerm’ ‘(’ Expression ‘,’ Expression ‘)’ | ‘isIRI’ ‘(’ Expression ‘)’ | ‘isURI’ ‘(’ Expression ‘)’ | ‘isBLANK’ ‘(’ Expression ‘)’ | ‘isLITERAL’ ‘(’ Expression ‘)’ | RegexExpression

[45] RegexExpression ::= RegexExpression[46] IRIrefOrFunction ::= IRIref ArgList?[47] RDFLiteral ::= String ( LANGTAG | ( ‘^^’

IRIref ) )?[48] NumericLiteral ::= NumericLiteralUnsigned |

NumericLiteralPositive | NumericLiteralNegative

[49] NumericLiteralUnsigned ::= INTEGER | DECIMAL | DOUBLE[50] NumericLiteralPositive ::= INTEGER_POSITIVE |

DECIMAL_POSITIVE | DOUBLE_POSITIVEDutch-Belgian Database Day 2010 (DBDBD 2010)November 22, 2010

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Appendix: EBNF terminals (1)[57] IRI_REF ::= ‘<’ ( [^<>"{}|^`\]-[#x00-#x20])*

‘>’ [58] PNAME_NS ::= PN_PREFIX? ‘:’ [59] PNAME_LN ::= PNAME_NS PN_LOCAL [60] BLANK_NODE_LABEL ::= ‘_:’ PN_LOCAL [61] VAR1 ::= ‘?’ VARNAME [62] LANGTAG ::= ‘@’ [a-zA-Z]+ ( ‘-’ [a-zA-Z0-

9]+ )* [63] INTEGER ::= [0-9]+ [64] DECIMAL ::= [0-9]+ ‘.’ [0-9]* | ‘.’ [0-9]+ [65] DOUBLE ::= [0-9]+ ‘.’ [0-9]* EXPONENT | ‘.’

([0-9])+ EXPONENT | ([0-9])+ EXPONENT

[66] INTEGER_POSITIVE ::= ‘+’ INTEGER [67] DECIMAL_POSITIVE ::= ‘+’ DECIMAL [68] DOUBLE_POSITIVE ::= ‘+’ DOUBLE [69] INTEGER_NEGATIVE ::= ‘-’ INTEGER [70] DECIMAL_NEGATIVE ::= ‘-’ DECIMAL [71] DOUBLE_NEGATIVE ::= ‘-’ DOUBLE [72] EXPONENT ::= [eE] [+-]? [0-9]+ [73] STRING_LITERAL1 ::= ‘ ( ( [^#x27#x5C#xA#xD] ) | ECHAR

)* "’" Dutch-Belgian Database Day 2010 (DBDBD 2010)November 22, 2010

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Appendix: EBNF terminals (3)[83] VARNAME ::= ( PN_CHARS_U | [0-9] )

( PN_CHARS_U | [0-9] | #x00B7 | [#x0300-#x036F] | [#x203F-#x2040] )*

[84] PN_CHARS ::= PN_CHARS_U | ‘-’ | [0-9] | #x00B7 | [#x0300-#x036F] | [#x203F-#x2040]

[85] PN_PREFIX ::= PN_CHARS_BASE ( ( PN_CHARS | ‘.’ )* PN_CHARS )?

[86] PN_LOCAL ::= ( PN_CHARS_U | [0-9] ) ( ( PN_CHARS | ‘.’ )* PN_CHARS )?


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Graphically Querying RDF Using RDF-GL

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