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Introduction

CSIE, Da-Yeh University

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History of Software Development Traditional Programming Paradigm

Behind schedule, costly, and unreliable. Structured Programming (1970’s)

Systematical analysis of the problems. Does not mirror the real world entities.

Object Oriented Programming (1980’s – 1990’s) Object technique is a packaging scheme to create

software units. Use classes to represent the real world entities. Web service take advantages of the OO technology.

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Component-based Development A component is a piece of software that satisfies

It must be deployable on its own It must publish and adhere to a programming interface.

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Component-based Development The limitation of using components

It takes a lot more effort to develop components that is reusable.

It is difficult to find the right components. It is hard to coordinate the releases of new components.

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Client Server Design

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Internet Design

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Application Server Architecture

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Distributed Computing The computing tasks are distributed over networks. Components extended at different computers must be

able to communicate with each other. Interface and response Security

Client

ClientInfrastructure

Proxy Proxy

Application

internet

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Distributed Computing Different technology

Object Management Group (OMG) – Common Object Request Broker Architecture (CORBA)

Microsoft – Distributive Component Object Model (DCOM)

IBM – Distributive System Object Model (DSOM) Sun Micro – Remote Method Invocation (RMI)

Components from different technology communicate with each other through a bridge. COM/CORBA bridge Poor interoperability

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Distributed Computing Infrastructure Microsoft’s DCOM

Shipped with versions of Windows NT beginning with version 4.0 and including Windows 2000.

Provide both local and remote COM capabilities. It is now an inherent part of Win32-based platforms.

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N-tier Web-based Application The client-tier uses browsers as the user interface. The middle-tier provides all the business logic and

processes. The information-tier is the information tier.

Client-tier Middle-tier Information-tier

data data

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Alternative to Web Service Screen Scraping: retrieving data from other HTML

documents. What are the disadvantages of using screen scraping?

HTMLHTMLWeb page

Middle Tier DatabaseApplication

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Web Service Technology Address the issue of poor interoperability. Use open standard. Easy to debug.

Web services use text-based protocols. Use XML as the standard for exchanging

information.

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Definition of Web Service Web services are software programs that use XML to

exchange information with other software via internet protocol.

Characteristics of web service Web services are programmable. Web services are based on XML. Web services are self-describing (WSDL). Web services are discoverable (UDDI).

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Web Service Architecture Protocols The core principles drive the design and

implementation of WS architecture protocols Message orientation Protocol composability Autonomous services Managed transparency Protocol-based integration

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Benefits over Distributed Computing Companies can expose and access web services using

technology already in place. Web service is more interoperable. Nearly all major software vendors have agreed to use

the same core standards.

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Challenge of the Web Service SOAP, WSDL, UDDI are still in draft. Royalty fees may required for some standards. Lack of standard security procedure. Defining and guaranteeing QoS.

Slow response time Infrequent update Inability to handle large number of requests

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Web Service Architecture

UDDIRegistry

WSDLDocument

client Web Service

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① Query Registry to locate service② Refer to WSDL documents③ Access WSDL documents④ Provide data to interact with web

service⑤ Send SOAP message request⑥ Send SOAP message response

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Web Service Terminology - SOAP SOAP (Simple Object Access Protocol)

A common way to package messages that are exchanged between two processes.

A common set of serialization techniques for the data that is exchanged.

A mechanism that allows Remote Procedure Calls (RPC) to be made across a heterogeneous set of platforms.

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Web Service Terminology – XSDL XSDL (XML Schema Definition Language)

XSDL defines the layout of and the constraints on an XML document.

XSDL supplants a previous standard known as Data Type Definition (DTD).

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Web Service Terminology - UDDI UDDI (Universal Description, Discovery, and

Integration) registry The most commonly known method of discovering

Web services. UDDI registry’s structure is similar to the phone book

White page: list contact information and descriptions of companies.

Yellow page: provide classification information about companies and details on companies’ electronic capability.

Green page: list technical data regarding services.

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Web Service Terminology - WSDL WSDL (Web Service Description Language)

It provides details about the functionality that is implemented, which messages are used to request the service, and the sequence in which the messages are exchanged.

It is XML-based format. Similar to the documentation to the ActiveX

components.

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Web Service Terminology - others XML ( eXtended Markup Language)

The main language used in Web service. GXA (Global XML Architecture)

A set of protocols defined by Microsoft and others. It provides an infrastructure that supports the most

commonly requested demands for commercial Web service: security and routing.

WS-Security It allows authentication established by one system to be

accepted by others (federated identity).

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Web Service Terminology - others WS-Routing

The typical mode for WS-Routing is to create a one-way path that the SOAP message must take.

WS-Referral A protocol directly related to WS-Routing. It allows for changes to the routing of a SOAP message

to be made dynamically.

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Delivering Web Service Service-oriented Architecture

Created by IBM. Service provider

A server or system makes a Web service available over network.

Provides a service interface, that enables other applications to access the service.

Service broker Service provider publishes its service to service broker. Service broker communicates with requesters and directs them

to the appropriate provider.

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Delivering Web Service Service requester

A networked server or system that access or employed a Web service.

Serviceprovider

Servicebroker

Servicerequester

bindpublish

find

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Web Service Life-cycle Stages

Creation Design, development, documentation, testing and distribution.

Publication Web service hosting and maintenance.

Promotion Directory services, value-added services and accreditation.

Sale Auditing and accounts management.

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ASP .Net Web Service Architecture

BrowserVB

ApplicationOffice

DocumentsOther Web

Service

Classic ASP

.ASP

ASP .Net

.ASPX

XML WebServices

.ASMX

Document-Style

Listener WSDL

Wrapper Classes

RPC-Style

Listener WSDL

BusinessObjects

DatabaseServer

SOAP Messages