WEB SERVICES
DAVIDE ZERBINO
Summary:
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Introduction
Definition
Web Service Model
Web Service Architecture
Web Service in action
Advantages
Web Service Development Lifecycle
Tools
References
Introduction
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A Software Service is a something that accepts
digital requests and returns digital responses e.g. C
function, a Java Object
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A computer application can be thought of
as a well-orchestrated set of services
Web Services are a new breed of software component
that is a language, platform, and location indipendent
Is accessible over the web
Web services are an abbrevation for Web of Services
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Distributed applications will be assembled
from a web of software services
Web Service
Is registred and can be located through
a Web service registry.
 Communicate using XML message over
standard Web protocols.
 Support loosely-coupled connections
between systems.
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Definition of Web Service
“A Web service is an interface that
describes a collection of operations that
are network-accessibile through
standardized XML messaging.”
Heather Kreger
IBM Software Group
The Web Services Model
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The Web service architecture is based upon the interactions
between three roles:
application that is looking for and invoking an interaction
Service
with a service
Registry owner of the services
Service
Service publish
searchable
registry where service provider
Requestor
Provider
their service descriptions and where service find service
The Web Services Model
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Others element are:
Service
Description
Service
Registry
Service
Description
Service
Requestor
Service
Provider
Service
The Web Services Model
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Others element are:
Service
Description
Contains details of the interface and
implementation of the service
Service
Description
It is a software module deployed on the
network-accessible platforms provided by
the service provider
Service
The Web Services Model
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The interactions involve the publish, find and bind operation
Service
Registry
Publish
Find
Service
Requestor
Bind
Service
Provider
The Web Service Stack
UDDI
Service
Discovery
UDDI
Service
publication
WSDL
Service
Description
SOAP
XML-Based
Messaging
HTTP, FTP, email, MQ, etc
Network
Quality of services
Service Flow
Management
WSFL
Requirements
Security
Standard Tecnologies
The Network
Web services must be network-accessible
For its ubiquity
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HTTP is the standard network protocol for internetavailable Web Services
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Others network protocols are SMTP, FTP and for intranet
domain: MQSeries, CORBA
XML-based Messaging
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Represent the use of XML as the basis for the messaging
protocol
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The current industry standard for XML messaging is
SOAP
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IBM, Microsoft, Sun and others submitted SOAP to the
W3C
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SOAP (Simple Object Access Protocol)
 Is a simple and lightweight XML-based mechanism for
exchanging structured data beetween network
applications
SOAP
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Lightweight communication protocol
For communication between applications
one-way, request/response, multicast, etc..
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Designed to communicate via HTTP
Not tied to any component technology
Not tied to any programming language
Based on XML
Simple and extensible
SOAP
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SOAP consists of three parts:
 An envelope that defines a framework for describing
what is in a message
 A set of encoding rules for expressing istances of
application-defined data types
 A convention for representing remote procedure calls
and responses
SOAP
Application
web service
Application
1
4
3
2
SOAP
SOAP
Network protocol
Network protocol
Request/Response
Service Description:
From XML to Web services
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Service provider comunicates all the specifications
through service description
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The service description combined with SOAP
infrastructure hides details as platform, programming
language from the service requestror’s application
and the service provider’s Web Service
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Web service uses WSDL for base-level service
description
WSDL
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WSDL: Web Service Definition Language
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is an XML-based language used to define Web
Services and describe how to access them
Industry standard W3C
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Service
Implementation
Definition
Service
Port
Service
Interface
Definition
Binding
PortType
Message
Type
Discovery and Publication:
UDDI
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Stands for Universal Description, Discovery and
Integration
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Defines a way to publish and discover information
about web services
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Collaboration between Microsoft, IBM, Ariba that
resulted in the creation of web service registry
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Not standard
UDDI
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Defines a data structure standard for representing
service description information in XML
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The core component of the UDDI project is the UDDI
business registration, an XML file used to describe a
business entity and its Web services
UDDI
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The UDDI Business Registry can be used at a business
level
– To check whether a given partner has particular Web
service interfaces.
– To find companies in a given industry with a given
type of services.
– To locate information about how a partner or intended
partner has exposed a Web service in order to learn
the technical details required to interact with that
service
WSFL Overview
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Web Service Flow Language (WSFL) is an XML language
for the description of Web Services Composition
It is possible to produce web services by composing web
services
 Intra-enterprise web services might collaborate to
present a single Web Service Interface to the public
 Web services from different eneterprises might
collaborate to perform business to business transactions
Service Flow described how service-to-service
communications, collaborations and flows are performed.
Web Service in Action: B2B
Customer
Supplier
Warehouse
Credit Bureau
Check validity
Service
Account Service
Advantages
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Interoperability:
 Any web services can interact with any other web
service
Ubiquity:
 Web services communicate using HTTP and XML.
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Low Barrier to Entry:
 The concepts behind web services are easy to
understand and toolkits are frely available from
many vendors
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Industry Support:
 All the major vendor are supporting SOAP and the
surrounding web services standards
Web Services Development
Lifecycle
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The development lifecycle can have four phase:
– BUILD :
» development and testing of the web service implementation
» definition of the services interface description
» definition of the service implementation description
– DEPLOY :
» publication of the services interface and service implementation
– RUN :
» The web service is available for invocation
» The web service is fully deployed, operational and networkaccessible from the services provider
» Now the service requestor can perform the find and bind
operations
– MANAGE :
» Covers ongoing management and administration of the web
services application
Tools
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Microsoft SOAP Toolkit 2.0
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Microsoft Visual Studio .NET and .NET Framework
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Apache SOAP Toolkit and AXIS
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IBM Web Services Toolkit
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SUN JavaTM 2 Platform, Enterprise Edition (J2EE)
Example:
Airport Weather Service
Airport Weather
Interface:
getLocation()
getWind()
getTemperature()
getSky()
getPressure()
getHumidity()
getSummary()
More informations:
Web Interface:
http://live.capescience.com/AirportWeather/index.html
References
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About SOAP :
http://www.w3c.org/TR/soap
About WSDL :
http://www.w3c.org/TR/wsdl
About UDDI :
http://www.uddi.org
About WSFL :
http://www.ibm.com/software/webservices
Other Papers
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About Web service Architecture:
 Web Services Conceptual Architecture (WSCA
1.0) -Heather Kreger - IBM SW Group
About Web service development lifecycle:
 Web Services Development Concepts (WSDC
1.0) -Peter Brittenham- IBM SW Group
About Web service model:
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Web Services : Building Blocks for Distributed
System -Graham Glass -
The End
Web Server in Action (2/2)
Application
WSDL
SOAP
HTTP
Interoperability
XML
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XML: eXtensible Markup Languages
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A version of HTML that allows any kind of data to be
represented in a simple and portable way
<giocatore id = 212>
<nome> Davide <\nome>
<cognome> Zerbino <\cognome>
<\giocatore>