WEB SERVICES

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WEB SERVICES

• DAVIDE ZERBINO

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Summary

• Introduction
• Definition
• Web Service Model
• Web Service Architecture
• Web Service in action
• Advantages
• Web Service Development Lifecycle
• Tools
• References

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Introduction

• A Software Service is a something that accepts
  digital requests and returns digital responses
  e.g. C function, a Java Object

• 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

• Distributed applications will be assembled from a
  web of software services

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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
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The Web Services Model

• The Web service architecture is based upon the
  interactions between three roles

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The Web Services Model

• Others element are

Service
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The Web Services Model

• Others element are

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The Web Services Model

• The interactions involve the publish, find and
  bind operation

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The Web Service Stack
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The Network
Web services must be network-accessible

• HTTP is the standard network protocol for
  internet-available Web Services

• Others network protocols are SMTP, FTP and for
  intranet domain MQSeries, CORBA

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XML-based Messaging

• Represent the use of XML as the basis for the
  messaging protocol

• The current industry standard for XML messaging
  is SOAP

• IBM, Microsoft, Sun and others submitted SOAP to
  the W3C

• SOAP (Simple Object Access Protocol)
• Is a simple and lightweight XML-based mechanism
  for exchanging structured data beetween network
  applications

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SOAP

• Lightweight communication protocol
• For communication between applicationsone-way,
  request/response, multicast, etc..
• Designed to communicate via HTTP
• Not tied to any component technology
• Not tied to any programming language
• Based on XML
• Simple and extensible

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SOAP

• 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

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SOAP
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3
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Service DescriptionFrom XML to Web services

• Service provider comunicates all the
  specifications through service description

• The service description combined with SOAP
  infrastructure hides details as platform,
  programming language from the service
  requestrors application and the service
  providers Web Service

• Web service uses WSDL for base-level service
  description

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WSDL

• WSDL Web Service Definition Language

• is an XML-based language used to define Web
  Services and describe how to access them

• Industry standard W3C

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Discovery and PublicationUDDI

• Stands for Universal Description, Discovery and
  Integration
• Defines a way to publish and discover information
  about web services
• Collaboration between Microsoft, IBM, Ariba that
  resulted in the creation of web service registry
• Not standard

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UDDI

• Defines a data structure standard for
  representing service description information in
  XML
• 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

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UDDI

• 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

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WSFL Overview

• 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.

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WSFL Overview

• Composition of Service
• Flow Model execution sequence of activities
• Global Model Interactions of services
• Recursive Composition scalability
• It is layered on the top of Web Services
  Description Language(WSDL) that is used for
  description of service interface and their
  protocol bindings

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Web Service in Action B2B
Customer
Supplier
Credit Bureau
Warehouse
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Advantages

• Interoperability
• Any web services can interact with any other web
  service

• Ubiquity
• Web services communicate using HTTP and XML.

• Low Barrier to Entry
• The concepts behind web services are easy to
  understand and toolkits are frely available from
  many vendors

• Industry Support
• All the major vendor are supporting SOAP and the
  surrounding web services standards

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Web Services Development Lifecycle

• 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 network-accessible 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

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Tools

• Microsoft SOAP Toolkit 2.0
• Microsoft Visual Studio .NET and .NET Framework
• Apache SOAP Toolkit and AXIS
• IBM Web Services Toolkit
• SUN JavaTM 2 Platform, Enterprise Edition (J2EE)

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ExampleAirport Weather Service

• Interface
• getLocation()
• getWind()
• getTemperature()
• getSky()
• getPressure()
• getHumidity()
• getSummary()

Airport Weather

• More informations
• Web Interface
• http//live.capescience.com/AirportWeather/index.h
  tml

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References

• 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

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Other Papers

• 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
• Web Services Building Blocks for Distributed
  System -Graham Glass -

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The End
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Web Server in Action (2/2)
Interoperability
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XML

• XML eXtensible Markup Languages

• A version of HTML that allows any kind of data to
  be represented in a simple and portable way

Davide
Zerbino