“ Declarative Updates for RDF Graphs: A n Introduction t o the Language RUL ”

“Declarative Updates for RDF Graphs: An Introduction to the Language RUL”

Kllapi Herald (M945)Nomikos Vangelis (M917)

01/03/2008

Paper Presentation

Query Languages for RDF/RDFS

• SPARQL (W3C Recommendation)

• ICS-FORTH RQL (RDFSuite, Atlas)

• SeRQL (Sesame)

• RDQL

• others….

RQL - A Brief Introduction• declarative query language for RDF/RDFS

• relies on a typed data model!!!– literal, resource, class, property, meta-class, bag, seq, alt types– for error detection and safety– for performance (e.g better storage)

• follows a functional approach– (e.g subclassof(), superclassof(), leafclass, domain(), range())

• separation of three layers:– meta-schema (e.g. meta-classes such as rdfs:Class)– schema– data

Why???

University RDF Schema – An Example

Module

Person

Staff

Economics Maths

Student

AcademicStaff NonAcademicStaff GraduateStudent

TeachingAssistant

UnderGraduateStudent

takes

teaches

assistsWith

Literal

foaf:name

RQL vs SPARQL - Schema Querying

• Example 1: “Which classes can appear as domain and range of the property teaches?”

• SPARQLPREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#> .SELECT ?X, ?YWHERE { ?X teaches ?Y .

?X rdf:type rdfs:Class . ?Y rdf:type rdfs:Class . }

• RQL

SELECT $X, $Y FROM {$X}teaches{$Y}

$X, $Y are variables bound to schema classes

RQL vs SPARQL - Schema Querying

• Example 2: “Find all properties that have range Module.”

• SPARQL

PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#> .SELECT ?PWHERE { ?P rdf:type rdf:Property .

?P rdfs:range Module . }

• RQL

SELECT @PFROM @P{;Module}

@P is a variable bound to property

RQL vs SPARQL - Basic Data Queries

• Example 3: “Find all GraduateStudents.”

• SPARQLPREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> . SELECT ?XWHERE { ?X rdf:type GraduateStudent . }

• RQLa) GraduateStudent

b) SELECT X FROM GraduateStudent{X}

Equivalent queries

RQL vs SPARQL - Basic Data Queries• Example 4: “Find all modules and their classes that Koubarakis teaches.”

• SPARQLPREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .SELECT ?X , ?ZWHERE { ?X rdf:type Person .

?X teaches ?Y .?Y rdf:type ?Z .?X foaf:name ?N .FILTER(regex(?N, “Koubarakis”) . }

• RQLSELECT Y , $ZFROM {X;Person}teaches{Y;$Z} , {X;Person}foaf:name{N}WHERE N = “Koubarakis”USING NAMESPACE foaf = &http://xmlns.com/foaf/0.1/

Y;$Z retrieves the

class of resource Y

RQL - More Complex Queries• Example 5: “Find all UnderGraduateStudents and the number of modules they

take.”SELECT X, CFROM UnderGraduateStudent{X}WHERE C = COUNT( SELECT Y

FROM {X}takes{Y;Module} )

• Example 6: “Find the persons who are NonAcademicStaff but not TeachingAssistants.”( SELECT X FROM NonAcademicStaff{X} ) minus ( SELECT Y FROM TeachingAssistant{Y} )

• Example 7: “Find the TeachingAssistant resources which have also been classified under UnderGraduateStudent.”SELECT XFROM TeachingAssistant{X} WHERE exists Y in UnderGraduateStudent SUCH THAT X=Y

RQLvs SPARQL – A ComparisonFeatures SPARQL RQL

Negation NO YES

Aggregate Functions

(i.e min, max, sum, avg, count)

NO YES

Nested SubQueries NO YES

Optional YES NO

Quantifiers

(i.e exists,forall)

NO YES

Graph Construction YES NO

Set Based Queries NO YES

RQL has some very interesting features that are not present at SPARQL yet!!!

Do we need more?

• We presented one more query language!

• Are we happy only with SELECT and ASK queries?

• Is it useful to have a way to update RDF data?– dynamic environments (e.g Grid Metadata)

RUL – A companion for RQL

• a declarative update language for RDF

• relies on RQL and on its typed data model (ICS-FORTH )

• each RUL operation always result in a consistent state of the updated graph(i.e effects and side-effects of each RUL operation)

• does not deal with – schema updates - blank nodes– containers - collections

• we will present the semantics of RUL in an informal way by a series of examples.

INSERT for Class Instances

• Goal– insert new class instances and classify them– insert new classification links for existing class instances

• SyntaxINSERT QualClassExp(ResourceExp)[FROM VariableBinding][WHERE Filtering][USING NAMESPACE NamespaceDefs]

• Example: “Make the resource with URI http://www.di.uoa.gr/Koubarakis an instance of the class AcademicStaff.”

INSERT AcademicStaff(&http://www.di.uoa.gr/Koubarakis)

INSERT for Class Instances

A

C

BD

1. INSERT A(&r4)

2. INSERT D(&r1)

&r1 &r2 &r3&r4

3. INSERT A(&r1)

4. INSERT B(&r1)

5. INSERT C(&r2)

No changes

DELETE for Class Instances• Goal

– delete a class instance – delete classification links

• SyntaxDELETE QualClassExp(ResourceExp)[FROM VariableBinding][WHERE Filtering][USING NAMESPACE NamespaceDefs]

• Example: “Delete all instances of class Person except for the resources with URIs http://www.di.uoa.gr/Koubarakis and http://www.di.uoa.gr/Zoi.”

DELETE $C(X)FROM $C{X}WHERE $C=Person AND ( X != &http://www.di.uoa.gr/Koubarakis AND

X != &http://www.di.uoa.gr/Zoi )

DELETE for Class InstancesA

C

B

L

M

K

N

Literal

Literal

P1

P2

&r4&r1

&r2

&r3

&r5

“str1”

P1

“str2”

“str3”

P2

P1

“str4”

P1

1. DELETE B(&r1)2. DELETE B(&r3)3. DELETE C(&r2)4. DELETE M(&r4)

5. DELETE L(&r5)P1

REPLACE for Class Instances• Goal

- replace an existing class instance with a new one

• SyntaxREPLACE QualClassExp (OldResourceExp NewResourceExp)[FROM VariableBinding][WHERE Filtering][USING NAMESPACE NamespaceDefs]

• Example: “The information that Manolis is academic staff is incorrect. The correct information is that Koubarakis is academic staff.”

REPLACE AcademicStaff(&http://www.di.uoa.gr/Manolis &http://www.di.uoa.gr/Koubarakis )

Replace for Class Instances

A

C B

“str1”

“str2”

Literal

&r4

&r1

&r2

&r3

P1

P1

1. REPLACE A(&r1 r1_new)

&r1_new

2. REPLACE B(&r2 &r4)

P1

3. REPLACE A(&r3 &r3_new)

&r3_new

REPLACE is not equivalent to a DELETE followed by an INSERT

A

B LiteralP1

“str1”&r1

P1

REPLACE B(&r1 &r2)

A

B LiteralP1

“str1”&r1

P1

DELETE B(&r1)

INSERT B(&r2)

&r2

&r2

REPLACE classification for Class Instances

• Goal– modify the classification of a class instance

• Syntax

REPLACE OldQualClassExp NewQualClassExp (ResourceExp)[FROM VariableBinding][WHERE Filtering][USING NAMESPACE NamespaceDefs]

• Example: “KT finished! We want to reclassify Zoi as instance of class GraduateStudent.”

REPLACE TeachingAssistant GraduateStudent(&http://www.di.uoa.gr/Zoi)

REPLACE classification for Class Instances

A

C

B

D

K

Literal

Literal

“str2”

“str1”

P1

P2

P1P2&r1

&r3

&r2

1. REPLACE A D(&r1)

2. REPLACE B K(&r2)

3. REPLACE B K(&r3)

No changes!

INSERT for Property Instances• Goal

– insert new property instances to existing resources

• SyntaxINSERT QualPropertyExp(SubjectExp, ObjectExp)[FROM VariableBinding][WHERE Filtering][USING NAMESPACE NamespaceDefs]

• Example: “Make the resource http://www.di.uoa.gr/Koubarakis teach the resource http://www.di.uoa.gr/KT.”

INSERT teaches(&http://www.di.uoa.gr/Koubarakis, &http://www.di.uoa.gr/KT)

INSERT for Property Instances

A B

C

P1

P2

&r3

&r1

&r2

&r4

P1P1

1. INSERT P2(&r3, &r4)

P2


P2


No changes!

DELETE for Property Instances• Goal

– remove instatiation links

• SyntaxDELETE QualPropertyExp(SubjectExp, ObjectExp)[FROM VariableBinding][WHERE Filtering][USING NAMESPACE NamespaceDefs]

• Example: “Delete the resource http://ww.di.uoa.gr/Koubarakis as teacher of KT.”

DELETE teaches(&http://www.di.uoa.gr/Koubarakis, &http://ww.di.uoa.gr/KT)

DELETE for property instances

A

B C

DP1

P2

P1

P2

P2

&r1

&r2

&r3

&r4

&r5 &r6

1. DELETE P1(&r1, &r3)


P1


REPLACE for Property Instances

• Goal– replace the subject or the object of a property instance

• SyntaxREPLACE QualPropertyExp (OldSubjectExp[<-NewSubjectExp], OldObjectExp[<-NewObjectExp])[FROM VariableBinding][WHERE Filtering][USING NAMESPACE NamespaceDefs]

• Example: “Make Zoi teach KT instead of Koubarakis.”

REPLACE teaches(&http://www.di.uoa.gr/Koubarakis&http://www.di.uoa.gr/Zoi,

&http://www.di.uoa.gr/KT)

REPLACE for Property Instances

A

B

C

D Literal

Literal

Literal

P1

P2

P3

&r1 &r2

&r3

&r4“str2”

“str1”

P2

P3

1. REPLACE P2(&r2 &r3, "str1")

P2

2. REPLACE P2(&r2 &r1, "str1")

3. REPLACE P3(&r4, “str2“ “str3”)

“str3”

No changes!

REPLACE classication for Property Instances• Goal

– modify the classification of one or more property instances

• Syntax

REPLACE OldQualPropertyExp NewQualPropertyExp(SubjectExp, ObjectExp)[FROM VariableBinding][WHERE Filtering][USING NAMESPACE NamespaceDefs]

• Example: “Make Koubarakis not teach KT! Koubarakis takes KT! ”

REPLACE teaches takes(&http://www.di.uoa.gr/Koubarakis, &http://www.di.uoa.gr/KT)

REPLACE classication for Property Instances

A B

C D

Literal

&r1

&r3

&r2&r4

&r5

“str1”

P3

P3

P1

P2 P4

P5

P4

P5

P1

P2

1. REPLACE P2 P1(&r1, &r3)

P1

2. REPLACE P3 P1(&r2, “str1”)



P5


P4 No changes!

Update Sequences

• The easy way– we can express sequences of updates by writing multiple RUL

statements one after the other

• The RUL way– sequences of primitive updates inside a single RUL statement

• Sequences of Updates – 2 types– of the same kind (e.g. a lot of insertions)– of different kinds (multiple INSERT, DELETE or REPLACE

clauses before the FROM clause of an update statement)

Update Sequences Examples

• Example: “Insert the resource with URI http://www.di.uoa.gr/KT as instance of the class Module and make resource Koubarakis its teacher.”

INSERT Module(&http://www.di.uoa.gr/KT) , teaches(&http://www.di.uoa.gr/Koubarakis ,

&http://www.di.uoa.gr/KT)

• Example: “All TeachingAssistants who assistsWith KT must take the lesson as UnderGraduateStudent.”

DELETE assistsWith(X,&http://www.di.uoa.gr/KT )REPLACE TeachingAssistantUnderGraduateStudent(X)INSERT takes(X, &http://www.di.uoa.gr/KT )FROM TeachingAssistant{X}WHERE {X} assistWith {&http://www.di.uoa.gr/KT }

order of execution does matter

SPARQL/Update (SPARUL)• supported by Hewlett-Packard

• it uses a syntax derived from SPARQL

• express updates to an RDF store

• SPARQL/Update provides the following facilities:– Insert new triples to an RDF graph – Delete triples from an RDF graph – Perform a group of update operations as a single action– Add a new RDF Graph to a Graph Store– Remove an RDF graph from a Graph Store

SPARQL Update - Examples• Example 1: “Make the resource with URI http://www.di.uoa.gr/Koubarakis an

instance of the class AcademicStaff.”

PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .INSERT { <http://www.di.uoa.gr/Koubarakis> rdf:type AcademicStaff }

• Example 2: “Delete all UnderGraduate Students who takes KT.”

DELETE FROM <http://www.di.uoa.gr/Students> { ?X rdf:type UnderGraduateStudent}

WHERE { ?X takes <http://www.di.uoa.gr/KT> }

graph

Remarks

It supports Graph Management and inherits all the advantages (and disadvatages) of SPARQL

But…

It lacks formal/informal semantics!!!

Conclusion

• A lot of effort on Query Languages for RDF data retrieval

• No W3C Reccomendation for RDF Updates

• Each system has its own way

So…

We are waiting for W3C recommendation!!!

Thank you!!!

[email protected]

[email protected]

Links• RQL: http://139.91.183.30:9090/RDF/RQL/

• Sesame RQL: http://www.openrdf.org/doc/rql-tutorial.html

• RUL: http://139.91.183.30:3026/RULdemo/demo/

• SPARQL: http://www.w3.org/TR/rdf-sparql-query/

• SPARQL/Update: http://jena.hpl.hp.com/~afs/SPARQL-Update.html

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“ Declarative Updates for RDF Graphs: A n Introduction t o the Language RUL ”

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