Web Services

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Web Service Definitions

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UDDI Consortium definition:

Self-contained, modular business application that have open, Internet-oriented, standards-based interfaces

World Wide Web consortium (W3C)

Software application identified by a URI, whose interfaces and bindings are capable of being defined, described and discovered as XML artifacts. A Web Service supports direct interactions with other software agents using XML-based messages exchanged via Internet-based protocols.

The Challenge of B2B integration across Web

Middleware and EAI do not provide tools to automate business processes between companies Companies will have to agree to use the

same middleware platform, the same workflow solution, and a specific name and directory server

Not possible!

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B2B integration before Web Services

Ariba and CommerceOneProvide broking services that allow binding to

routing messages of different companies EDIFACT

Provides standard templates for messages and their contents

One EDIFCT implementation was in WalmartExtension to the CORBA ORB

GIOP (General Inter- ORB protocol) specified communication between ORBs

IIOP protocol (Internet Inter-ORB protocol) translated the GIOP calls into TCP/IP

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Service-oriented paradigm

Web services work on the paradigm that functionality made available by a company will be exposed as a service

Service is a procedure, method or object with a stable published interface that can be invoked by clients.

The invocation is made by a program

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A Web Service is a software application with a published and stable programming interface not a set of Web pages

How does this impact B2B integration?

Each company exposes its functionality as a Web Service

B2B integration can run on standard Web technologies

Web services act as the entry point into local information systems

Web Services can also be used within the enterprise system or even a LAN to integrate enterprise applications

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Web Services Technologies

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Service Description & Discovery

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Common base language

interfaces

business protocols

properties and semantics

Vertical standards

dire

ctorie

s

Common meta-language used as a basis to describe the different aspects of a service. XML is used

Interface definition in the absence of implicit context Web Services Description Language (WSDL)

Set of rules supported by service that govern the conversations between clients and Web services.Emerging standards are Web Services Conversation Language (WSCL & Business Process Execution Langauge for Web Services (BPEL)

Non functional properties (cost, quality), descriptions etc. associated with a service Universal Description Discovery and Integration (UDDI)

Define specific interfaces, protocols, properties and semantics that services offered in certain applications should support

Register services and Allow service users to search for & locate new services

Service Interactions

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transport

basic and secure messaging

protocol infrastructure (meta-protocols)

middleware (horizontal) protocols

Communication network is hidden behind a transport protocol HTTP is the most common

Format and package the information to be exchanged. Simple Object Access Protocol (SOAP)

Protocols which facilitate and coordinate the execution of business protocols WS-Coordination tries to standardize these protocols and the way WSDL and the way WSDL and SOAP should be used

Provides properties like reliability and transaction WS-Transaction implements transactional properties

Web Services Architecture: two views

Internal Architecture:Allows internal operations to be exposed thru

the Web Another tier on top of other tiers of an

enterprise system

External Architecture:Defines how Web Services discover and

interact with each other Requires cross-organizational interactions

across the Internet Relies on standards

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Service Composition

Basic Service:Web service implemented by accessing the

local system

Composite Service:Web service implemented by invoking other

Web Services

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Summary

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Web Services Definition: Software application identified by a URI, whose interfaces and

bindings are capable of being defined, described and discovered as XML artifacts. A Web Service supports direct interactions with other software agents using XML-based messages exchanged via Internet-based protocols.

Service definition:Service is a procedure, method or object with a stable published

interface that can be invoked by client programs. Two aspects of Web Services:

Allow Internal Operations to be exposed to the WebDefines how Web Services discover and interact with each other

Standards are emerging to describe services, register and search services, format messages.

(the material in this topic is based on Web Services: Concepts, Architectures and Applications by Alonso, Casati, Kuno, Machiraju)