Querying the RDF: Small Case Study in the Bicycle Sale Domain

Querying the RDF: Small Case Study in the

Bicycle Sale Domain

Ondřej Šváb, Vojtěch Svátek,

Martin Kavalec, Martin Labský

VŠE, University of Economics, Prague

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Querying the RDF: Small Case Study in the Bicycle Sale Domain

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Content

• 1. Integration of web analytic tools

• 2. RDF/S

• 3. Bicycle Sale Domain in RDF/S

• 4. Sesame

• 5. RDF query languages

• 6. Example of HTML interface usage

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1. Integration of web analytic tools

• Analytic tools from RAINBOW

• http://rainbow.vse.cz

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2. RDF/S

• RDF – Resource description framework– Assertional language for information representation– Reification– RDF graph– Several types of serialization: RDF/XML, N-Triples,

N3

• RDFS – Resource description framework schema– Semantic language for RDF– „core vocabulary“, enables to define properties, classes

and their taxonomy (hierarchy)

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3. Bicycle Sale Domain in RDF/S

• Typical extracted attributes:– Name of bike, price, picture, components

<rdf:Description rdf:about="http://www.bikepedlar.co.uk/Giant_terrago.htm"><bike:hasCompany rdf:resource="http://www.bikepedlar.co.uk"/><bike:hasName>Giant Terrago F/S 3</hasName><bike:hasPrice>350.00</hasPrice><bike:hasBikePart rdf:resource="http://rainbow.vse.cz/bikes/bikes.rdf#alivio"/>

</rdf:Description>

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Example of reification

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4. Sesame

• System for manipulating with RDF/S– http://www.openrdf.org

• Four functional modules:– Query Module– Admin Module– Extract Module– Explore Module

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5. RDF query languages

• RDQL– Implemented according to HP specification

• RQL– Original proposal by ICS-FORTH

• SeRQL– Developed as part of system Sesame

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Pros/Cons RDQL RQL SeRQL

Path expr. + + +

RDFS support

- ++ +

Optional path exp.

- + ++

Reified statements

+ + ++

Strings comp.

- + +

Features of RDF query languages

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Path expressions:

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Namespaces in queries

using namespaceweb = <!http://rainbow.vse.cz/schema/webpage.rdfs#>,xsd = <!http://www.w3.org/2001/XMLSchema#>,bike = <!http://rainbow.vse.cz/schema/bikes.rdfs#>,comp = <!http://rainbow.vse.cz/schema/company.rdfs#>,meta = <!http://rainbow.vse.cz/schema/meta.rdfs#>,pict = <!http://rainbow.vse.cz/schema/picture.rdfs#>,rdfs = <!http://www.w3.org/2000/01/rdf-schema#>,rdf = <!http://www.w3.org/1999/02/22-rdf-syntax-ns#>

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RQL/SeRQL 1

RQL

select domain(@predicate), @predicate, range(@predicate)

from {} @predicate {}where @predicate =

pict:hasWidth

SeRQL

select domain, rangefrom {<pict:hasWidth>} <rdfs:domain> {domain},{<pict:hasWidth>} <rdfs:range> {range}

1Q: Find restrictions (domain and range) of property hasWidth.

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RQL/SeRQL 2

RQL

select X, name, picture, widthfrom {X : bike:RetailOffer }

bike:hasName {name},{X} bike:hasPicture {picture}.

pict:hasWidth {width}

where name like "l*" and width < 70

2Q: Find all retail offers with name starting with letter ”l” and having a picture with width lower than 70.

SeRQL

select X, name, picture, width from {X} <serql:directType> {<bike:RetailOffer>}, {X} <bike:hasName> {name}, {X} <bike:hasPicture> {Y} <pict:hasWidth> {width}

where name like "l*" and width < "70"^^<xsd:integer>

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RQL 3/13Q: Find all retail offers of bicycles that have a concrete bike component. Output

the name of company that offers the bike, the picture of retail offer, the price of bike (offer). Retrieve the retail offer even if the URL of picture is not known.

(select web, company, price, picture, namefrom {X : bike:RetailOffer } bike:hasCompany {web : comp:Company }. comp:companyName {company}, {X} bike:hasPrice {price}, {X} bike:hasPicture {picture}, {X} bike:hasBikeProduct {idtyp}. bike:name {name}where idtyp=data:part1)Union …

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…

Union

(select web, company, price, null, name

from {X : bike:RetailOffer } bike:hasCompany

{web : comp:Company }. comp:companyName {company},

{X} bike:hasPrice {price},

{X} bike:hasBikeProduct {idtyp}. bike:name {name}

where idtyp=data:part1 and not

(X in select X

from {X} bike:hasPicture {picture}))

RQL 3/2

Operator “in” - subquery

Result = S1un. S2

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SeRQL 3

select prv, web, company, price, picture, namefrom {prv} <serql:directType> {<bike:RetailOffer>}; <bike:hasPrice> {price}; [<bike:hasPicture> {picture}]; <bike:hasBikeProduct> {idtyp}, {idtyp} <bike:name> {name}, {prv} <bike:hasCompany> {web} <rdf:type> {<comp:Company>}; <comp:companyName>

{company}where idtyp = <data:part1>

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RQL 4 – query over reified statements

select X, obj, certainty

from {X : rdf:Statement } rdf:subject {reifSubj},

{X} rdf:predicate {reifPred},

{X} rdf:object {reifObj},

{X} meta:hasMeta {obj}. meta:certainty {certainty}

where certainty > "0.9"

4Q: Find all statements that have certainty higher than 0.9.

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SeRQL 4 –query reified statements

select obj, certainty

from { {reifSubj} reifPred {reifObj} }

<meta:hasMeta> {obj} <meta:certainty> {certainty}

where certainty > "0.9"^^<xsd:double>

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6. Example of HTML interface (usage)

- Three parts

- First for specifying the query

- Second for result

- Third for „detailed“ results in certain regard

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HTML interface

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Initial query

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Following query – [About]

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Following query – [Picture]

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Future work

– Integration, transformation– More active cooperation with Sesame– HTML interface and better querying – Testing with greater amount of real-world data

Thank you for your attention

Querying the RDF: Small Case Study in the Bicycle Sale Domain

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