Web Services Architecture Overview

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NCCU Computer Center

May 6,2002

參考資料 [1]Don Box,“A brief History of SOAP” ,XML.COM, 2001 [2]Jakob Nielsen,”The End of Homemade Websites”,us

eit.com, Oct 2001 [3]Venu Vasudevan,” Web Services Primer”,XML.COM,

April 2001 [4]David Orchard,”Web Services Pitfalls”,Feb 2002 [5]Heather Kreger,” Web Services Technical Architectur

e”,Java ONE Conf 2002, 2002 [6]Scoot Seely,”SOAP : Cross Platform web service dev

elopment using XML”,Prentice Hall PTR,2002

參考資料 (2) [8]Patrick Cauldwell,Rajesh Chawla,Vivek Chopra,Gary

Damschen,Chris Dix ,Tony Hong,Francis Norton,Uche Ogbuji“Professional XML Web Services”,Wrox,2001

[9]Roger Wolter,”XML Web Services Basics”,Microsoft,Dec 2001

[10]David A.Chappell , Tyler Jewell,”Java Web Services”,Oreilly,March 2002

[11]James Goodwill ,”Using SOAP with Tomcat”,O’reilly Network,Feb 2002

[12] James Snell,”Web Services Interoperability”,XML.COM,Jan 2002

Web services is evolution not revolution

There is nothing new about Web services

Web Services will change everything--Heather Kreger

Java ONE Conference 2002

Emerging Technologies

Web Services Lead Architect

IBM

Presentation Agenda Introduction to Web Services Core Protocols :SOAP、WSDL and UDDI Implementations of Web Services Interoperability issues The Missing Part of Web Services

Introduction to Web Services A Web Services is an application component accessi

ble via standard web protocols. Web Services expose components for remote executi

on using the Web technology and infrastructure. Applications can call services implemented by diffe

rent language which are executed on different platforms.(theoretically…)

Web Services-Technical View Invocation:SOAP/XML Service Description:WSDL/XSD/RDF Service Discovery:UDDI

Web Services-Technical View

Image Source: Heather Kreger

How Web Services Work Client sends a HTTP request (for example)to Server Server recognizes which method should be invoked

by its requesting URL Server converts the types of inbound parameters pro

perly then invoke the method Server converts the type of return value then generat

e the response SOAP message Response message to the client.

How Web Services Work(2)

Vendor Implementations HP E-Speak Apache SOAP and AXIS Microsoft .NET Framework

A Successful Case Dollar Rent A Car Systems,Inc integrate its booking

system with Southwest Airlines Co. by web services technologies.

Dollar Rent A Car Systems:Sun Solaris Server Southwest Airlines:Compaq OpenVMS You can reserve Dollar’s car without leaving Southw

est’s site.

A Successful Case

A Successful Case

The Core Protocols SOAP WSDL UDDI

SOAP SOAP is never acronym of “Simple Object Access Protocol”

http://www-106.ibm.com/developerworks/library/ws-ref8.html One of the most externally visible decisions was about the nam

e of this protocol. It was decided that because the acronym "SOAP" had such large mind-share out in the industry, we did not want to change the name to something relatively unknown -- like XML Protocol. Once we decided to keep the name "SOAP," the question then became whether we wanted SOAP to continue to mean Simple Object Access Protocol. So we voted and decided that "SOAP" should no longer be an acronym and just be known as SOAP, with no meaning behind the letters

SOAP What were defined in SOAP

The unified XML-format of messages Encoding Style:How to encode the parameters and the ret

urn value. APRC Convention

SOAP is not always used in RPC The protocol transports SOAP messages doesn’t nee

d to be HTTP.

SOAP-RPC Model Defined in SOAP 1.1 Section 7 To Invoke a method call ,following informations are

needed URI of target object Method name Parameters (Optioinal) header data

The message body must be encoded according Section 5.

SOAP-Message Exchanging Model SOAP message supports multiple exchanging model

s One way Request/Response Broadcast Chain

SOAP-Message Exchanging Model

“End point” means the soap processing unit of message(ie: a webservice)

“Intermediaries” mean end points which play the roles of sender and receiver simultaneously .

SOAP-Message Exchanging Model

SOAP-Message Exchanging Model

End Point Behavior Examine the SOAP message to see if it contains any

information addressed to this end point Examine if the “mustUnderstand” attribute is “1”,if t

he attribute is 1 and end point didn’t know it then a fault code must return.

Remove and edit the “actor” attribute properly Process the message assigned to this end point Forward to next point (if current end point is not the

last one in the message chain)

An Example

An Example Shop Website to fillInId Service fillInId Service to placeOrder Service placeOrder Service to shipOrder Service

WSDL An XML Vocabulary (similar in purpose to IDL) Describes the interfaces for web services and h

owto invoke the services WSDL includes

Service Description Service Interface Definition WSDL provides all IDL capabilities

WSDLWSDL

UDDI Universal Description, Discovery, and Integratio

n Partnership among industry and business lead

ers Initiated by Ariba, IBM, and Microsoft Now over 300 UDDI community members

IBM UDDI Registry https://www-3.ibm.com/services/uddi/v2beta/protect/regis

try.html

UDDI

Interoperability issues This is What break the most beautiful dream of Web

Service. Versioning Problems

SOAP 1.2 didn’t backward compitiable with SOAP1.1. The SOAP servers support SOAP 1.2 will by default retur

n an fault SOAP message when encountered a SOAP 1.1 message is sent.

Interoperability issues(2) Vendor dependent:

Due to the incompleteness of SOAP 1.1 Spec or the vendors deliberately missunderstand of the spec.

Dispite some fixing by your own ,the Apache SOAP can’t work with services implemented by VS.NET.

There are solutions for interoperability of famous Vendors like Microsoft with Java.Fixing it need the detail knowledges of WSDL.

This is such a serious problem that there is a working orgnization called “SOAPBuilder” target at interoperability problems.

The Missing Part of WS Transactions

XAML、 XLANG(Microsoft， used in its biztalk framework)

Security XKMS(XML Key Management Specification) by Microso

ft/Verisign

Process/Flow pattern description XLANG，WSFL

Web Services Roadmap Web Services(RPC or Messaging) Web Agent (DAML) Semantic Web (RDF)

DEMO Java Web Services .NET Web Services Java Pet Store Microsoft Pet Store

Summary We are moving from a web composed of docum

ents to a web that also contains business services

Web services is a standards-based way to make applications discoverable and usable on the Internet (intranet)

The industry is focusing on UDDI, SOAP,and WSDL as the foundations of the Web services approach

Summary(2) Most people agree that Web Services provide t

he application models of the next generation but there are long way to go before public acceptance

Q & A