adding semantics to web services standards kaarthik sivashanmugam, kunal verma, amit shethamit sheth...

Adding Semantics to Web Services Standards

Kaarthik Sivashanmugam, Kunal Verma,

Amit Sheth and John Miller

LSDIS Lab, Department of Computer Science

The University of Georgia

Outline

• Challenges in web services adoption• Web services conceptual stack and

semantics at different layers• Semantics for web service usage lifecycle• METEOR-S project at LSDIS lab• Semantic publication and discovery of web

services• Conclusion, References and Q&A

Web Service Conceptual Stack1

Description

Messaging

Network

Description:Web Service Description Language (WSDL)– To describe Web Service interfaces and implementations

–Details in WSDL files (data types, operations, binding details, access location) are used for service invocation

Messaging:(SOAP)– XML based messaging protocol

Network:(HTTP)– Network protocol

1 [Kreger]

Web Service Conceptual Stack1

Publication:(UDDI)– To make service descriptions available for search

Discovery:(UDDI)

– To locate service descriptions Publication

Discovery

Description

Messaging

Network

Flow

Flow:(BPEL4WS, WSCI etc.)– To compose web services to form a composite web service / process

1 [Kreger]

BIG Challenges

• Machine understandable descriptions

• Dynamic discovery and service selection

• Scalability in discovery mechanisms

Hypothesis: Semantics is the most important enabler

METEOR-S at LSDIS lab

• Adding semantics to different layers of Web services conceptual stack

• Applying* semantic Web techniques to industry accepted Web services standards for better Web service description – to solve the problems of scalability and heterogeneity in Web

service discovery, selection and composition

* Use of ontologies to provide underpinning for information sharing and semantic interoperability

Semantics at Different Layers

Publication

Discovery

Description

Messaging

Network

Flow

Description Layer: Why: • Reason about the functionality of the services and the

semantics of the operational data

How: • Using Ontologies to semantically annotate WSDL

constructs (conforming to extensibility allowed in WSDL specification version 1.2) to sufficiently explicate the semantics of the – data types used in the service description and– functionality of the service

Present scenario: • WSDL descriptions are mainly syntactic (provides

operational information and not functional information)

• Semantic matchmaking is not possible

Semantics at Different Layers (contd..)

Publication

Discovery

Description

Messaging

Network

Flow

Publication and Discovery Layers: Why: • Enable scalable, efficient and dynamic publication and

discovery (machine processability / automation)

How: • Use of ontology to categorize registries based on domains

and characterize them by maintaining the1. properties of each registry2. relationships between the registries

• Capturing the WSDL annotations in UDDI

Present scenario:

• Suitable for simple searches ( like services offered by a provider, services that implement an interface, services that have a common technical fingerprint etc.)

• Categories are too broad

• Automated service discovery (based on functionality) and selecting the best suited service is not possible

Semantics at Different Layers (contd..)

Publication

Discovery

Description

Messaging

Network

Flow

Flow Layer: Why: • Design (composition), analysis (verification), validation

(simulation) and execution (exception handling) of the process models

• To employ mediator architectures for automated composition, control flow and data flow based on requirements

How: • Using

– Functionality/preconditions/effects of the participating services

– Knowledge of conversation patterns supported by the service– Formal mathematical models like process algebra– Simulation techniques

Present Scenario: • Composition of Web services is static.• Dynamic service discovery, run-time binding, analysis and

simulation are not supported directly

Semantics in METEOR-S

Publication

Discovery

Description

Messaging

Network

Flow

MWSDI: Scalable Infrastructure of Registries for Semantic publication and discovery of Web Services

MWSDI: Semantic Annotation of WSDL (WSDL-S)

MWSCF: Semantic Web Process Composition Framework

Scope of Semantic Web with respect to Web Services

Gen. Purpose,Broad Based

Scope of AgreementTask/ App

Domain Industry

CommonSense

Degre

e o

f Ag

reem

en

t

Info

rmal

Sem

i-Form

al

Form

al

Agreement About

Data/Info.

Function

Execution

Qos

Oth

er d

ime

nsio

ns:

how

ag

reem

ents

are

re

ach

ed

,…

Current Semantic Web Focus

Semantic Web Processes

Lots of Useful

SemanticTechnology

(interoperability,Integration)

Semantics for Web Services

• Data/Information Semantics– Formal definition of data in input and output messages of a web service– for discovery and interoperability– by annotating input/output data of web services using ontologies

• Functional/Operational Semantics– Formally representing capabilities of web service– for discovery and composition of Web Services– by annotating operations of Web Services as well as provide preconditions and effects; Annotating

TPA/SLA

• Execution Semantics– Formally representing the execution or flow of a services in a process or operations in a service– for analysis (verification), validation (simulation) and execution (exception handling) of the process

models– using State Machines, Petri nets, activity diagrams etc.

• QoS Semantics– Formally describing operational metrics of a web service/process– To select the most suitable service to carry out an activity in a process– using QoS model [Cardoso and Sheth, 2002] for web services

Data/ Information

Semantics

Development/ Description/ Annotation WSDL, WSEL

DAML-S

Meteor-S (WSDL Annotation)

Publication/ Discovery

UDDI

WSIL, DAML-S

METEOR-S (P2P model of registries)

Composition

BPEL, BPML, WSCI, WSCL,

DAML-S, METEOR-S

(SCET,SPTB)

Execution

BPWS4J, Commercial BPEL Execution Engines,

Intalio n3, HP eFlow

Semantics for Web Service usage life cycle

Data/ Information

Semantics


WSDL, WSEL

DAML-S


UDDI

WSIL, DAML-S




Development/ Description/ Annotation

Composition

Execution


DAML-S, METEOR-S

(SCET,SPTB)


Functional/ Operational

Semantics


WSDL, WSEL

DAML-S


UDDI

WSIL, DAML-S





Composition

Execution


DAML-S, METEOR-S

(SCET,SPTB)


QoSSemantics


WSDL, WSEL

DAML-S


UDDI

WSIL, DAML-S





Composition

Execution


DAML-S, METEOR-S

(SCET,SPTB)


ExecutionSemantics


WSDL, WSEL

DAML-S


UDDI

WSIL, DAML-S





Composition

Execution


DAML-S, METEOR-S

(SCET,SPTB)



WSDL, WSEL

DAML-S


UDDI

WSIL, DAML-S




Semantics Required for Web Processes

ExecutionSemantics

QoSSemantics

Functional/ Operational

Semantics

Data/ Information

Semantics


Composition

Execution


DAML-S, METEOR-S

(SCET, SPTB)


METEOR-S components for Semantic Web Services

• Discovery Infrastructure (MWSDI)– Semantic Annotation of Web Services 1

– Semantic Peer-to-Peer network of Web Services Registries 2

• Composer– SCET: Service Composition and Execution Tool 3

– Semantics process template builder and Process generator 4

– QoS Management• Specify, compute, monitor and control QoS (SWR algorithm) 5

• Orchestrator (Under development)

– Analysis and Simulation 6

– Execution

– Monitoring 6

1 [Sivashanmugam et al.-1], 2 [Verma et al.], 3 [Chandrasekaran et al.], 4 [Sivashanmugam et al.-2], 5 [Cardoso et al.], 6 [Silver et al.]

Search for services to book air ticket (using categories)*

• unspsc-org: unspsc:3-1

– Travel, Food, Lodging and Entertainment Services • Travel facilitation

– Travel agents

» Travel agencies

• Services: 3 records found.– AirFares

Returns air fares from netviagens.com travel agent

– Hotel reservationsReservations for hotels in Asia, Australia and New Zealand

– Your Vacation SpecialistsWeb enabled vacation information

• Providers: 2 records found.

* Search carried out in one of the Universal Business Registries

Search for services to book air ticket (using keywords)*

• air ticket– 1 record with name air tickets booking

• airticket, ticketbooking, airtravel, air travel, travel agent, airticketbooking, air ticket booking, travel agency, travelagency

– 0 records were returned

• travelagent– 1 record with name travelagent test

• 4 services: BookFlight, cancelFlightBooking etc.• Descriptions say that both these services are “XML based Web services”• No URL for WSDL

• Travel– 15 records. Purpose/functionality understood from descriptions

• 2 services : TravelBooks• 4 services : TravelInformation• 2 services : Reservation and cancallation of travel tickets• 1 service : Emergency Services for travellers• 1 service : Travel documentation and itinerary• 5 services : Description is ambiguous/not present

* Search carried out in one of the Universal Business Registries

Semantic Discovery: Overview

• Annotation and Publication– WSDL file is annotated using ontologies and the annotations are captured

in UDDI

• Discovery– Requirements are captured as templates that are constructed using

ontologies and semantic matching is done against UDDI entries• Functionality of the template, its inputs, outputs, preconditions and effects are

represented using ontologies

• Use of ontologies – brings service provider and service requestor to a common conceptual

space– helps in semantic matching of requirements and specifications

Use of ontologies enables shared understanding between the service provider and service requestor

Semantic Publication and Discovery

WSDL

<Operation>

<Input1>

<Output1>

Service Template

Operation:buyTicket

Input1:TravelDetails

Output1:Confirmation

Annotations

Publish

Search

UDDI

Class

TravelServices

Class

DataClass

Operations

subClassOf subClassOf

subClassOfsubClassOf subClassOf subClassOf

ClassTicket

Information

ClassTicket

Booking

ClassTicket

Cancellation

ClassConfirmation

Message

Operation:cancelTicket

Input1:TravelDetails

Output1:Confirmation

For simplicity of depicting, the ontology is shown with classes for both operation and data

WSDL-S (WSDL with Semantic Annotation)

• Mapping Input and Output Message Parts to Ontology– XML Schema elements used in Input/Output messages do not reflect the semantics of the data involved

in Web Service operation– Use of ontologies or standard vocabulary* brings service provider and requestor to common conceptual

space providing well defined semantics for operational data

• Mapping Operations to Ontology– Service selection involves discovering appropriate WSDL description and locating an operation to

invoke– Operations with same signature could have different functionalities– Ontology or vocabulary depicting functionality is used for annotation

• Additional tags to represent pre-conditions and effects of each operation– Preconditions and effects are added for each operation– Can be optionally used for service discovery and selection

* RosettaNet Business/Technical dictionary or ebXML Core Component catalog/dictionary

The focus of our work is not in developing ontologies for representing functionality/preconditions/effects but to use such ontologies for semantic annotation

Annotation Syntax*

• Each Operation in WSDL is annotated using an fully qualified attribute name-value pair in the operation element under portType element. The attribute name is operation-concept

• Each Message part is annotated using a fully qualified attribute name-value pair in the part element under message element. The attribute name is onto-concept

• Preconditions and effects are respectively represented using fully qualified additional tags with the names precondition and effect. These elements have two attributes name (optional) and precondition-concept (or effect-concept). Each operation can have multiple precondition and effect elements.

* conforms to extensibility support in WSDL version 1.2

WSDL Annotation Example

<?xml version="1.0" encoding="UTF-8"?><wsdl:definitions xmlns:LSDISOnt=lsdis.cs.uga.edu//METEORS/TravelServiceOntology.daml ….. > <wsdl:message name="OperationRequest"> <wsdl:part name="in0" type="tns:TravelDetails" LSDISExt:ontoconcept= "LSDISOnt:TicketInformation"/> </wsdl:message> <wsdl:portType name="TravelArragement"> <wsdl:operation name="buyTicket" parameterOrder="in0" LSDISExt:operation-concept="LSDISOnt:TicketBooking"> <wsdl:input message="intf:OperationRequest" name="buyTicketRequest"/> <wsdl:output message="intf:OperationResponse" name="buyTicketResponse"/> <LSDISExt:precondition name="ValidCreditCard" LSDISExt:precondition-concept="LSDISOnt:ValidCreditCard"/> </wsdl:operation></wsdl:definitions>

Semantics in UDDI

• tModels are used to categorize and characterize service entries in UDDI (limited form of semantics)

• Our approach uses categorizes* (using metadata constructs tModels and CategoryBags) the services in UDDI based on the semantic annotations

* similar to [Paolucci et al.]

Semantic Categorization of Services in UDDI*

Service

KeyedReferenceGroup(SemanticGroupTModelKey)


CategoryBag TmodelKey:OperationalTModelKey, Value:TicketBooking, Name:buyTicket

TmodelKey:InputTModelKey, Value:TicketInformation

TmodelKey:OutputTModel, Value:ConfirmationMessage

* conforming to UDDI Version 3 spec [UDDI-v3]

TmodelKey:OperationalTModelKey, Value:TicketCancellation, Name:cancelTicket

TmodelKey:InputTModelKey, Value:TicketInformation

TmodelKey:OutputTModel, Value:ConfirmationMessage

For the example discussed earlier: Travel Arrangement Service with two operations buyTicket and cancelTicket


Service



CategoryBag TmodelKey:OperationalTModelKey, Value:TravelOnto:TicketBooking, Name:buyTicket

TmodelKey:InputTModelKey, Value:TravelOnto:TicketInformation

TmodelKey:OutputTModelKey, Value:GeneralTradeOnto:ConfirmationMessage

TmodelKey:OperationalTModelKey, Value: TravelOnto:TicketCancellation, Name:cancelTicket

TmodelKey:InputTModelKey, Value: TravelOnto:TicketInformation

TmodelKey:OutputTModelKey, Value: GeneralTradeOnto: ConfirmationMessage

Operation-ontology mapping in WSDL for buyTicket operation

<operation name=“buyTicket” operation-concept=“TravelOnto:TicketBooking”>



Service





TmodelKey:OutputTModelKey, Value: GeneralTradeOnto:ConfirmationMessage

TmodelKey:OperationalTModelKey, Value:TravelOnto:TicketCancellation, Name:cancelTicket

TmodelKey:InputTModelKey, Value: GeneralTradeOnto:TicketInformation

TmodelKey:OutputTModel, Value: GeneralTradeOnto:ConfirmationMessage

Input Message part-ontology mapping in WSDL for buyTicket operation

<part name=“input1” type=“tns:TravelDetails” onto-concept=“TravelOnto:TicketInformation”>



Service





TmodelKey:OutputTModelKey, Value: GeneralTradeOnto:ConfirmationMessage

TmodelKey:OperationalTModelKey, Value:TravelOnto:TicketCancellation, Name:cancelTicket

TmodelKey:InputTModelKey, Value: GeneralTradeOnto:TicketInformation

TmodelKey:OutputTModel, Value: GeneralTradeOnto:ConfirmationMessage

Output Message part-ontology mapping in WSDL for buyTicket operation

<part name=“output” type=“xsd:String” onto-concept=“GeneralTradeOnto:ConfirmationMessage”>


Service

KeyedReferenceGroup(SemanticGroupTModel)



CategoryBag

TmodelKey:OperationalTModel, Value:OperationConcept, Name:OperationName

TmodelKey:InputTModel, Value:Input_Concept_W

TmodelKey:InputTModel, Value:Input_Concept1_Y

…….

TmodelKey:OutputTModel, Value:Output_Concept_X

TmodelKey:OutputTModel, Value:Output_Concept1_Z

…….

Same for all UDDIentries

OperationalTModelInputTModel

OutputTModelSemanticGroupTModel

* conforming to UDDI Version 3 spec


Discovery using UDDI API

• Services are matched if their CategoryBags are a subset of the CategoryBag used in search (find_service)

• According to UDDI version 3 specification CategoryBags can be constructed using KeyedReferenceGroups. So groups can be constructed using the semantics of operation, inputs, outputs, preconditions and effects and search can be carried out.

Discovery using UDDI API• Our implementation used UDDI Version 1 API

– KeyedReferenceGroups are not supported– Each operation is grouped with its operation-concept, input and output onto-

concepts each as a keyedReference in the keyedReferenceVector as

tModelKey = “OpTModel” KeyValue = “operation-concept” KeyName = “OpName” tModelKey = “InTModel” KeyValue = “onto-concept” KeyName = “OpName”

tModelKey = “OutTModel” KeyValue = “onto-concept” KeyName = “OpName”

OpTModel: Key for the tModel representing functional semantics of the operation named “OpName” in a WSDL file linked to the UDDI entry

InTModel: Key for the tModel representing semantics of the inputs of the operation named “OpName” in the WSDL

OutTModel: Key for the tModel representing semantics of the outputs of the operation named “OpName” in the WSDL

operation-concept: Fully qualified Id of a class in a functional ontology represented by OpTModel

onto-concept: Fully qualfied Id of a class in a ontology that is used to annotate inputs (or outputs) represented by InTModel (or OutTModel)

Summary of Steps in Discovery

1. Services selection based on the functional requirements• Using operation-ontology mapping

2. Ranking based on semantic similarity based on input/output semantics of candidate services and requirement template

• Using message part-ontology mapping

3. Optional step includes semantic similarity based on semantics of preconditions/effects of the candidate services and requirement template

• Using precondition and effect tags

Conclusions

• Semantics is the enabler to address the problems of scalability, heterogeneity (syntactic and semantic), machine understandability faced by Web services

• Semantics can be applied to different layers of Web Services conceptual stack

• Semantics for Web Services can be categorized into atleast 4 different dimensions namely Data, Functional, Execution and Quality.

References

• [Kreger] http://www-3.ibm.com/software/solutions/webservices/pdf/WSCA.pdf

• [Sivashanmugam et al.-1] Adding Semantics to Web Services Standards

• [Sivashanmugam et al.-2] Framework for Semantic Web Process Composition

• [Verma et al.] MWSDI: A Scalable Infrastructure of Registries for Semantic Publication and Discovery of Web Services

• [Chandrasekaran et al.] Performance Analysis and Simulation of Composite Web Services

• [Cardoso et al.] Modeling Quality of Service for Workflows and Web Service Processes

• [Silver et al.] Modeling and Simulation of Quality of Service for Composition of Web Services

• [Paolucci et al.] Importing Semantic Web in UDDI• [UDDI-v3] http://uddi.org/pubs/uddi-v3.00-published-20020719.htm

Thank you

adding semantics to web services standards kaarthik sivashanmugam, kunal verma, amit shethamit sheth...

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