© Copyright 2007 STI - INNSBRUCK Applying Reasoning to Instance Transformation Adrian Mocan, Mick...

© Copyright 2007 STI - INNSBRUCK www.sti-innsbruck.at

Applying Reasoning to Instance Transformation

Adrian Mocan, Mick Kerrigan, Emilia Cimpian

[email protected]

2www.sti-innsbruck.at

Overview

• Context• Ontology mappings and mapping rules• Grounding the mappings to WSML• Applying data mediation • Conclusions


Ontology-based Data MediationContext

• Mediation ScenarioBusiness Partner 2

Business Partner 1

Information System 2

communicate

Ontology 1

uses

hassource

Ontology 2

has target

usesInformation

System 1

Mediation Component

Target Ontology

Source Ontology

Storage

Mappings

Mappings

Source Instance

Target Instance

Ontology Mapping Tool

Run-time Data Mediator

inTermsOf

inTermsOf

• Mediation SolutionWeb Service Modeling Toolkit


Run-time Data Mediator

Abstract Mappings

Repr.

RulesGenerator

Instance

Source

ReasoningEnvironment

Mapping Rules

Mappings

Instance

Target

Ontologies

Abstract Mappings

Repr.

Abstract Mappings

Repr.

RulesGenerator

RulesGenerator

Instance

Source

Instance

Source

ReasoningEnvironmentReasoning

Environment

Mapping Rules

Mappings

Instance

Target

Instance

Target

OntologiesOntologies

• Input– Source Instances + Source/Target Schemas

– Ontology Mappings

• Output– Target Instances


Ontology Mappings (1)

• Abstract representation of mappings– Alignment format developed as part of the KW NoE project

Schema elements (e.g. concepts, attributes)

Restriction on the schema elements (e.g. allowed values for an attribute)

Concept2Concept (C2C)Attribute2Attribute (A2A)Concept2Attribute (C2A)Attribute2Concept (A2C)

mapping(sourceEntity; [sourceEntityRestriction]; targetEntity; [targetEntityRestriction];

typeOfMapping)


Ontology Mappings (2)

• The Alignment Format – Not committed to any ontology representation language

• It doesn’t have a formal semantics

– It has an XML and an RDF serialization

• Why using such a mapping language?– Easier to manage mappings

• When parts of the alignment need to be updated

• When the mapped ontologies evolve

– Allows the effective usage of the mappings

Mappings needs to be grounded to a concrete formalism


Web Service Modeling Language (WSML) (1)

• Family of languages for Web Service Modeling Ontology (WSMO)

• WSML-Flight– Based on Datalog

• WSML-Rule– Extension of WSML-Flight based on Horn fragment of F-logic– Allows functions symbols and unsafe rules


Web Service Modeling Language (WSML) (2)

concept person hasChristianName ofType (0 *) _string hasSurname ofType (1 1) _string hasGender ofType (1 1) Gender dateOfBirth ofType (0 1) Date

concept book title ofType (1 1) _string hasAuthor ofType (0 *) author concept author subConceptOf person authorOf inverseOf(hasAuthor) ofType (0 *) book

instance crimeAndPunishment memberOf book title hasValue “Crime and Punishment" hasAuthor hasValue dostoyevsky

axiom authorshipFromAuthor definedBy authorship(?x, ?y):- ?x[authorOf hasValue ?y] memberOf author

F-Logic

person[hasChristianName =>>_string; hasSurname => _string; hasGender => Gender; dateOfBirth => Date].

book[title => _string; hasAuthor => author].

author::person[authorOf =>> book].

crimeAndPunishment:book.book[title -> “Crime and Punishment”; hasAuthor -> dostoyevsky].

FORALL X,Y authorship(X,Y) <- X:author[auhtorOf -> Y]


Mapping Rules in WSML

• The ontology mappings are grounded to WSML rules

• The target instances are “constructed” by these rules– Function symbols are used in order to generate new, unique

identifiers for these instances

mediated(source_instance, target_concept)

• WSML rules + source instances + source/target schema fragments are loaded into a reasoner– “pseudo-merged” ontology– The mediated data (i.e. the target instances) are retrieved by

querying this ontology


Running Examples

concept Person

hasChristianName ofType _string

hasSurname ofType _string

hasGender ofType Gender

dateOfBirth ofType Date

concept Date

day ofType _integer

month ofType _integer

year ofType _integer

concept Gender

instance _1 memberOf Gender

instance _2 memberOf Gender

instance _ memberOf Gender

concept Citizen

hasName ofType Name

hasSex ofType Sex

hasBirthday ofType Date

concept Name

hasFirstName ofType _string

hasSurname ofType _string

concept Date

day ofType _integer

month ofType _integer

year ofType _integer

concept Sex

instance M memberOf Sex

instance F memberOf Sex

instance N memberOf Sex

Source Ontology Target Ontology


Mapping Rules in WSMLClass to Class Mapping

mapping(o1#Person, o2#Citizen, C2C)

mediated(?x, o2#Citizen) memberOf o2#Citizen and mapped(o1#Person, o2#Citizen,?x):-

?x memberOf o1#Person

instance johnS

memberOf o1#Person

mediated(johnS, o2#Citizen)

memberOf o2#Citizen

mapped(o1#Person, o2#Citizen, johnS)


Mapping Rules in WSMLClass to Attribute Mappings

mapping( o1#Person, o2#Citizen.hasName , C2A)

mediated(?x,o2#Citizen)[hasName hasValue mediated(?x, o2#Name)] memberOf o2#Citizen:-

?x memberOf o1#Person and

mediated(?x,o2#Name)[?anAttribute hasValue ?aValue] memberOf o2#Name.

instance johnS memberOf o1#Person

mediated(?x,o2#Name)[…] memberOf

o2#Name

mediated(johnS,o2#Citizen)[hasName

hasValue mediated(johnS, o2#Name)]

memberOf o2#Citizen


Mapping Rules in WSMLAttribute to Attribute Mappings (1)

mapping(o1#Person.hasSurname, o2#Name.hasSurname, A2A)

mediated(?x,o2#Name)[hasSurname hasValue ?v] memberOf o2#Name:-

?x[hasSurname hasValue ?v] memberOf ?subCs and

?subCs subConceptOf o1#Person and mapped(?subCs,o2#Name,?x).

instance johnS[hasSurname

hasValue “Smith”] memberOf o1#Person

mapped(o1#Person, o2#Name, johnS)

mediated(johnS,o2#Name)[hasSurname

hasValue “Smith”] memberOf o2#Name

mapping(o1#Person, o2#Name, C2C)


Mapping Rules in WSMLAttribute to Attribute Mappings (2)

mapping(o1#Person.dateOfBirth, o2#Citizen.hasBirthDay, A2A)

mediated(?x,o2#Citizen)[hasBirthDay hasValue mediated(?i, o2#Date)] memberOf o2#Citizen:-

?x[dateOfBirth hasValue ?i] memberOf ?subCs and?subCs subConceptOf o1#Person and mapped(?subCs, o2#Citizen)mediated(?i,o2#Date)[?anAttribute hasValue ?aValue].

instance johnS[dateOfBirth hasValue

johnS_birthdate] memberOf o1#Person

mapped(o1#Person, o2#Citizen, johnS)

mediated(johnS_birthdate, o2#Date)[...]

mediated(johnS,o2#Citizen)[hasBirthDay

hasValue

mediated(johnS_birthdate, o2#Date)] memberOf o2#Citizen


Mapping Rules in WSMLAttribute to Class Mappings


Mapping Conditions

• Conditions that have to hold for the mapping to apply

• Three main types– Attribute occurrence conditions

– Attribute type conditions

– Attribute value conditions

Source

Target


Querying and Retrieving the Mediated Instances

?- ?x memberOf o2#Citizen Found < 1 > result to the query: (1) -- ?x = mediated(johnS, o2#Citizen)

?- mediated(johnS, o2#Citizen)[?y hasValue ?z] memberOf o2#Citizen and ?z memberOf ?avC. Found < 3 > results to the query: (1) -- ?z = o2#M, ?avC = o2#Sex, ?y=o2#hasSex (2) -- ?z = mediated(johnS,o2#Name), ?avC = o2#Name, ?y= o2#hasName (3) -- ?z = mediated(johnS_birthDate, o2#Date), ?avC = o2#Date, ?y = o2#hasBirthday

?- mediated(johnS, o2#Name)[?y hasValue ?z] memberOf o2#Name and ?z memberOf ?avC. Found < 2 > results to the query : (1) -- ?z = John, ?avC = string, ?y = o2#hasFirstName (2) -- ?z = Smith, ?avC = string, ?y = o2#hasSurname

...


Applying the Ontology-based Data Mediation

• SEEMP EU FP6 Project

• SemanticGov EU FP6 Project

• Rules, schemas and data to be mediated cannot be simply loaded in the reasoning space

• A set of optimizations have to be applied for an effective mediation task

• Minimize the size of the knowledge base to be queried (i.e. filtering)


Optimizations for the Instance Transformation Scenario

• Source Instance Filtering– Instances of unmapped entities can be directly discarded

• Mapping Filtering– Mappings that cannot applied to any of the source instances

don’t need to be transformed to rules

• Source and Target Ontology Filtering– Schema elements that are not relevant don’t need to be included

in the reasoning space

mapping(sourceEntity; [sourceEntityRestriction]; targetEntity; [targetEntityRestriction];

typeOfMapping)


Value Transformation Services

• Very often imply more than “re-arranging” the source values in the structure imposed by the target is needed

• Target values might need to be computed based on source values

• Value transformation services– Service calls embedded in the rules– The reasoner has the role of setting the parameters– Services are resolved after reasoning in a preprocessing phase

mapping(sourceEntity; [sourceEntityRestriction];targetEntity; [targetEntityRestriction];

typeOfMaping)

Transf. Service(serviceId, param)


Value Transformation ServicesExample

mediated(?X45,o2#Citizen)[o2#hasName hasValuehttp://example.org/concatService(?Y46,?Y47)] memberOf o2#Citizen :- ?X45[o1#hasChristianName hasValue ?Y46] memberOf o1#Person and ?X45[o1#hasSurname hasValue ?Y47] memberOf ?SC47 and ?SC47 subConceptOf o1#Person and mapped(?SC47,o2#Citizen,?X45) .

instance mediated(johnS, o2#Citizen) memberOf o2#Citizen o2#hasSex hasValue o2#M o2#hasName hasValue http://example.org/concatService("John","Smith") o2#hasBirthday hasValue mediated(johnS_birthDate, o2#Date)


Summary and conclusions

• Main principle of an instance transformation engine– Separation between mappings and rules– Grounding of mappings to WSML rules– Usage of a Datalog reasoner with function symbols

• Applying data mediation

• Future work– Extend and refine the optimization algorithms– Further Evaluation

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