Web Services 101Introduction to Web

Services

2110472 Computer Networks

Natawut Nupairoj, Ph.D.

Department of Computer Engineering

Chulalongkorn University

Outline

What is web service ? Any why ? Service-Oriented Architecture. Web Services Products. Existed and Future Applications. Trends and Future.

What is web service ?

“Next-generation service-oriented Internet applications.”

“Component-based software architecture.”

“A concept of a programmable Internet.”

OK, what really is web service ?

Well…nobody really knows for sure. Everyone has its own definition. Something in common

Software components with well-defined interfaces.

Communicating through XML-based messaging. Connecting via HTTP-based protocol.

Why then ?

Everybody is doing it !!!

No…that’s not a good answer!!!

Web Services Model

Driving Forces

E-business trends Flexible architecture. From RPC to messaging-centric model.

Business needs EAI – Enterprise Application Integration. B2B / G2G.

The Ultimate Goals

Web service is Platform independent. Implementation independent. Software Components.

Features Described using a service description language. Published to a registry of services. Discovered through a standard mechanism. Invoked through a declared API over a network. Composed with other services.

Service Oriented Architecture

Publish – Find – Bind.

ServiceRegistry

ServiceProvider

ServiceRequestor

Publish

Bind

Find

UDDI

SOAP

WSDL

Web Services Interoperability Stacks

Proposed to W3C by IBM and Microsoft in March 2001 Wire stack. Description stack. Discovery stack.

Wire Stack

Determine how a message is sent from the service requestor to the service provider.

Components HTTP (SMTP, FTP, RMI/IIOP, MQSeries). XML. SOAP.

“XML-based RPC over HTTP”

SOAP RPC Request

POST /bws/inventory.jws HTTP/1.0…

<?xml version=“1.0” encoding=“UTF-8”?><SOAP-ENV:Envelope

SOAP-ENV:encodingStyle=http://schemas.xmlsoap.org/soap/encoding/xmlns:xsd=http://www.w3.org/2001/XMLSchemaxmlns:SOAP-ENV=http://schemas.xmlsoap.org/soap/envelope/xmlns:xsi=http://www.w3.org/2001/XMLSchema-instance><SOAP-ENV:Body>

<doCheck><arg0 xsi:type=“xsd:string”>947-TI</arg0><arg1 xsi:type=“xsd:int”>1</arg1>

</doCheck></SOAP-ENV:Body>

</SOAP-ENV:Envelope>

SOAP RPC Response

HTTP/1.0 200 OK

…

<?xml version=“1.0” encoding=“UTF-8”?>

<SOAP-ENV:Envelope

SOAP-ENV:encodingStyle=http://schemas.xmlsoap.org/soap/encoding/

xmlns:xsd=http://www.w3.org/2001/XMLSchema

xmlns:SOAP-ENV=http://schemas.xmlsoap.org/soap/envelope/

xmlns:xsi=http://www.w3.org/2001/XMLSchema-instance>

<SOAP-ENV:Body>

<doCheckResponse>

<doCheckResult xsi:type=“xsd:boolean”>true</doCheckResult>

</doCheckResponse>

</SOAP-ENV:Body>

</SOAP-ENV:Envelope>

SOAP Messaging

<?xml version=“1.0” encoding=“UTF-8”?><SOAP-ENV:Envelope

SOAP-ENV:encodingStyle=http://schemas.xmlsoap.org/soap/encoding/xmlns:xsd=http://www.w3.org/2001/XMLSchemaxmlns:SOAP-ENV=http://schemas.xmlsoap.org/soap/envelope/xmlns:xsi=http://www.w3.org/2001/XMLSchema-instance><SOAP-ENV:Body>

<po xmlns=http://www.skatestown.com/ns/poid=“503383” submitted=“2001-12-06”><billTo>

<company>The Skateboard Warehouse</company><street>One Warehouse Park</street>…

</billTo>…

</po></SOAP-ENV:Body>

</SOAP-ENV:Envelope>

Description Stack

Describe the details of the service What a service does (provided methods). How a service is accessed (data format &

protocol). Where a service is located (e.g. URL).

WSDL / WSEL XML-based format. Service implementation and interface. Endpoint description.UDDI.

Discovery Stack

Provide service discovery mechanism. There are 2 levels

Inspection – discovering the service description given that service identifier (URL) is known. IBM’s ADS and Microsoft’s DISCO.

Directory – capabilities-based lookup. UDDI.

What are in the market ?

J2EE BEA – WebLogic Server. IBM – WebSphere SOAP toolkit. Sun – SunOne. Iona – XMLBus Macromadia – JRun 3.1 / JRun 4.0. Apache – Axis (SOAP API). University of Indiana – SOAP-RMI. Mind Electric – GLUE.

Microsoft’s .NET

Any existing applications ?

Yes…there are some… Dealersphere

National Auto Dealer Association. Car dealers to communicate with other

companies via ebXML and SOAP. Features?

Handling credit checks. Getting the exact color and car options. Locating the car at another dealer.

Any existing applications ?

Public eService Infrastructure (PSi) iDA Singapore. Integrate over 600 online services from several

government agencies. Ex:

Request for a new driver’s license. Service provided by Land Transport Authority of Singapore. However, citizen information is needed from Citizen

Department. And payment must be made online. Other services also need these information.

Future applications ?

Authentication services Microsoft’s Passport. Liberty Alliance.

Agent-based shopping. Internet syndication.

Conclusion

Web services is still unclear Open areas. Or just a hype!

Publish + find + bind = WSDL + UDDI + Soap

References

S. Graham et. al, “Building Web Services with Java”, SAMS Publishing, 2002.

http://www.webservices.org And others…

Questions ?