Web Services DescriptionWeb Services DescriptionLanguage (WSDL)Language (WSDL)

Wanasanan Thongsongkrit

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WSDL DevelopmentHistory at W3C WSDL 1.1

was submitted as a W3C Note by Ariba, IBM andMicrosoft

• March 2001• Merging 3 previous proposals:

• Microsoft’s SOAP Contract Language (SCL)• Service Description Language• IBM’s Network Accessible Service Specification

Language (NASSL)

WSDL 2.0 March 2006

not yet a W3C standard

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What WSDL is for

When you create a service, you typically do itbecause you want other people to use it.

In order for them to do that, they need to knowwhat information to send to the service, whatinformation the service is going to send back, andwhere to find the service in the first place.

It is much more helpful to have a standard,preferably human- and machine-readable, formatfor this information.

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What is WSDL?

is an XML document used to describe Web services: specifies

the location of the service the operations (or methods) the service

exposes

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WSDL Data Structure

WSDL does not presume that exchangeswill take place using a particular form ofcommunication Different services could combine

different interfaces using differentbinding, and could make them available atdifferent addresses

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The WSDLDocumentStructure

Abstract part : describes the messages it sends and

receives the operation associates a

message exchange patternwith one or more messages

Concrete part : specifies transport and wire format

details for one or moreinterfaces

a port (an endpoint) associatesa network address with abinding

a service which groupstogether endpoints thatimplement a common interface

WSDL specification

abstract part

types

messages

operations

port types

concrete part

bindings

services andports

Copyright Springer Verlag Berlin Heidelberg 2004

port andservice

binding

operation andport type

messages

abstractpart

concretepart

Copyright Springer Verlag Berlin Heidelberg 2004

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The WSDL DocumentStructure

definition of types........

definition of a message....

definition of a port.......

definition of a binding....

definition of a service

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Definitions

The definitions element defines namespaces. xmlna:xxx defines the aliases or prefixes for

namespaces of the actual elements that make upthe WSDL

targetNamespace, defines the namespace to whichthe items defined by the WSDL belong

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Abstract part

The data elements of anoperation

The data types used by theweb service (XML Schemasyntax used in general)

The operations performedby the web service and themessages that are involved.

DefinesElementabstract part

types

messages

operations

port types

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Abstract part

Message element Parts : name + type/element

PortType (Interface) element defines operations, whichare made up of messages Operations : One-way/Request-response/ Solicit-response /

Notification

operation andport type

messages

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Operation Types

The operation can send a messagebut will not wait for a responseNotification

The operation can send a request andwill wait for a responseSolicit-response

The operation can receive a requestand will return a responseRequest-response

The operation can receive a messagebut will not return a responseOne-way

DefinitionType

A service can proactively initiate the interaction (unlike IDLs) – operationcan invoke thus a service can also behave like a client

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Concrete part

port andservice

binding

concrete part

bindings

services andports

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InterfaceBinding

binding attributes are name (any name) type (points to the port type defined in the abstract part)

soap:binding attributes are style("rpc“ / "document”) Transport(Communication protocol : SOAP, Transport protocol : HTTP/SMTP)

operation element defines each operation that the port exposes. must also specify how the input and output are encoded

(literal(for document)/SOAP(for rpc))

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Port and Service

A service may have more than one endpoint,with each one defined by its own portelement.

The port element corresponds to a particularbinding, and includes information on how toaccess it (URI).

Different ports represent different bindings forthe same port type – allows the samefunctionality to be accessible via multipletransport protocols and interaction styles

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Reusability

abstract interfaces: reusable WSDL documents may import other WSDL

documents Some documents define abstract

interfaces, while other documents importthose definitions and make them concreteby defining bindings and addresses

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Using WSDL WSDL document

can be generatedfrom APIs.

service providerservice requestor

application object(client)

application object(service provider)

stub skeleton

WSDL ofservice provider

WSDL compiler(server side)

WSDL compiler(client side)

SOAP-basedmiddleware

SOAP-basedmiddlewareSOAP messages

WSDLgenerator

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Copyright Springer Verlag Berlin Heidelberg 2004

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WSDL and OtherStandards Generic service description language – WSDL Specific standards

Electronic Data Exchange (EDI) used in manufacturing SWIFT used in financial world

Possibility Hybrid : other standards + WSDL Independent WSDL as a wrapper for these standards so that the

systems that support them become Web enabled and canuse generic tools for Web access.

WSDL may not describe the entire service but only theinterface and protocol bindings. The details of theoperations will be hidden under a description that uses aspecification other than WSDL.

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WSDL 2.0

inherited most of the WSDL 1.1architectural principles, including layersof description, flexible authoring style ormodularization capability, andextensibility. Abstract Interface: Protocol Binding Service Endpoints

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WSDL 1.1 vs. WSDL 2.0

Flexible Authoring Styles

for WSDL definitions with a differentnamespace

for WSDL definitions with the samenamespace.

WSDL2.0

enables importing WSDL definitions definedin separate files with the same or differentnamespaces

WSDL 1.1

WSDL 2.0 Component Model

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WSDL 1.1 vs. WSDL 2.0

Namespace

http://www.w3.org/2004/08/wsdlWSDL2.0

http://schemas.xmlsoap.org/wsdl/WSDL 1.1

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WSDL 1.1 vs. WSDL 2.0 Message Exchange Patterns (MEPs)

Out-OnlyRobust Out-OnlyOut-InOut-Optional-In

Out-bound

In-OnlyRobust In-OnlyIn-OutIn-Optional-Out

In-bound

WSDL2.0

One-wayRequest-responseSolicit-responseNotification

WSDL 1.1

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Example : Messageexchange patterns

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WSDL 1.1 vs. WSDL 2.0

Supported Schema

supports also other schemas,such as RELAX NG andSchematron

WSDL 2.0

supports XML schemaWSDL 1.1

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Example: Amazon WSDL

http://www.awszone.com/

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More details

Understanding Web services https://www6.software.ibm.com/developerworks/educatio

n/ws-understand-web-services2/index.html First Look at WSDL 2.0

https://www.sdn.sap.com/irj/servlet/prt/portal/prtroot/docs/library/uuid/74bae690-0201-0010-71a5-9da49f4a53e2

Web Services Description Language (WSDL) Version2.0 Part 1: Core Language http://www.w3.org/TR/wsdl20/#intro