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Web Services Overview

This chapter provides an overview of Web Services. Chapter 2, "Oracle9iAS Web Services" describes the Oracle9iAS Web Services features, architecture, and implementation.

This chapter covers the following topics:

• What Are Web Services?

• Overview of Web Services Standards

• Scenario: Web Services with a Currency Converter Application

What Are Web Services?

Web Services consist of a set of messaging protocols, programming standards, and network registration and discovery facilities that expose business functions to authorized parties over the Internet from any web-connected device.

This section covers the following topics:

• Understanding Web Services

• Benefits of Web Services

• About the Web Services e-Business Transformation

Understanding Web Services

A Web Service is a discrete business process that does the following:

• Exposes and describes itself - A Web Service defines its functionality and attributes so that other applications can understand it. A Web Service makes this functionality available to other applications.

• Allows other services to locate it on the web - A Web Service can be registered in an electronic Yellow Pages, so that applications can easily locate it.

• Can be invoked - Once a Web Service has been located and examined, the remote application can invoke the service using an Internet standard protocol.

• Returns a response - When a Web Service is invoked, the results are passed back to the requesting application over the same Internet standard protocol that is used to invoke the service.

Web Services provide a standards based infrastructure through which any business can do the following:

• Offer appropriate internal business processes as value-added services that can be used by other organizations.

• Integrate its internal business processes and dynamically link them with those of its business partners.

Benefits of Web Services

The benefits for enterprises seeking to develop and use Web Services to streamline their business processes include the following:

• Support for open Internet standards. Oracle supports SOAP, WSDL, and UDDI as the primary standards to develop Web Services. Web Services developed with Oracle's products can inter-operate with those developed to Microsoft's .NET architecture.

• Simple and productive development facilities. Oracle provides developers with an easy-to-use and productive environment for developing Web Services using a programming model that is identical to that for J2EE applications.

• Mission critical deployment facilities. Oracle provides a mission-critical platform to deploy Web Services by unifying the Web Services and J2EE runtime infrastructure. Oracle9iAS Web Services provide optimizations to speed up Web Services responses, to scale Web Services on single CPUs or multiple CPUs, and to provide high availability through fault tolerant design and clustering.

  See Also: "Overview of Web Services Standards"

About the Web Services e-Business Transformation

The move to transform businesses to e-Businesses has driven organizations around the world to begin to use the Internet to manage corporate business processes. Despite this transformation, business on the Internet still functions as a set of local nodes, or Web sites, with point-to-point communications between them. As more business moves online, the Internet should no longer be used in such a static manner, but rather should be used as a universal business network through which services can flow freely, and over which applications can interact and negotiate among themselves.

To enable this transformation, the Internet needs to support a standards-based infrastructure that enables companies and their enterprise applications to communicate with other companies and their applications more efficiently. These standards should allow discrete business processes to expose and describe themselves on the Internet, allow other services to locate them, to invoke them once they have been located, and to provide a predictable response.

Web Services drive this transformation by promising a fundamental change in the way businesses function and enterprise applications are developed and deployed.

This e-Business transformation is occurring in the following two areas:

• Business Transformation with Web Services

• Technology Transformation with Web Services

About Business Transformation with Web Services

Web Services enables the next-generation of e-business, a customer-centric, agile enterprise that does the following:

• Expands Markets - Offers business processes to existing and new customers as services over the Internet, opening new global channels and capturing new revenue opportunities.

• Improves Efficiencies - Streamlines business processes across the entire enterprise and with business partners, taking action in real-time with up-to-date information.

• Reaches Suppliers and Partners - Creates and maintains pre-defined, systematic, contractually negotiated relationships and dynamic, spot partnerships with business partners who are tightly linked within supply chains.

About Technology Transformation with Web Services

Web Services enables enterprise applications with the following technology transformations:

• Development and Deployment - Web Services can be developed and deployed quickly and productively.

• Locating Services - Web Services allow applications to be aggregated and discovered within Internet portals, enterprise portals, or service registries which serve as Internet Yellow Pages.

• Integrating Services - Web Services allow applications to locate and electronically communicate with other applications within an enterprise and outside the enterprise boundaries.

• Inter-Operating Services - Web Services allow applications to inter-operate with applications that are developed using different programming languages and following different component paradigms.

Overview of Web Services Standards

This section describes the Internet standards that comprise Web Services, including:

• Simple Object Access Protocol (SOAP)

• Web Services Description Language (WSDL)

• Universal Description, Discovery, and Integration (UDDI)

Figure 1-1 shows a conceptual architecture for Web Services using these standards.

Figure 1-1 Web Services Standards

Text description of the illustration aswsv002.gif

Simple Object Access Protocol (SOAP)

The Simple Object Access Protocol (SOAP) is a lightweight, XML-based protocol for exchanging information in a decentralized, distributed environment. SOAP supports different styles of information exchange, including: Remote Procedure Call style (RPC) and Message-oriented exchange. RPC style information exchange allows for request-response processing, where an endpoint receives a procedure oriented message and replies with a correlated response message. Message-oriented information exchange supports organizations and applications that need to exchange business or other types of documents where a message is sent but the sender may not expect or wait for an immediate response.

SOAP has the following features:

• Protocol independence

• Language independence

• Platform and operating system independence

• Support for SOAP XML messages incorporating attachments (using the multipart MIME structure)

Web Services Description Language (WSDL)

The Web Services Description Language (WSDL) is an XML format for describing network services containing RPC-oriented and message-oriented information. Programmers or automated development tools can create WSDL files to describe a service and can make the description available over the Internet. Client-side programmers and development tools can use published WSDL descriptions to obtain information about available Web Services and to build and create proxies or program templates that access available services.

Universal Description, Discovery, and Integration (UDDI)

The Universal Description, Discovery, and Integration (UDDI) specification is an online electronic registry that serves as electronic Yellow Pages, providing an information structure where various business entities register themselves and the services they offer through their WSDL definitions.

There are two types of UDDI registries, public UDDI registries that serve as aggregation points for a variety of businesses to publish their services, and private UDDI registries that serve a similar role within organizations.

See Also: http://www.uddi.org for information on Universal Description, Discovery and Integration specifications.

Scenario: Web Services with a Currency Converter Application

To understand how Web Services work, consider a currency translation service that provides businesses with up-to-the-instant currency conversion information. Figure 1-2 shows the characteristics of such a Web Service.

A business has a financial management application which needs to check the conversion rate from one currency to another currency before completing a transaction. The financial management application sends a request to the currency conversion Web Service, it is processed, and a response is returned in real-time.

Using Web Services, there are two roles to consider, the role of the publisher that develops the currency conversion Web Service, and the role of the caller, the financial management application that uses the Web Service.

Figure 1-2 Currency Conversion Web Service

Text description of the illustration aswsv003.gif

Understanding the Publisher's Role

The publisher develops the currency conversion Web Service; the publisher's role includes the following:

• Develop the application - The currency conversion company develops a currency conversion application. The currency conversion application is developed in Java/J2EE or any other programming language.

• Publish the application interfaces - The currency conversion application has a set of formalized interfaces. These interfaces are published in WSDL.

• Register with a Web Service registry - The currency conversion company registers itself as a business entity and publishes its WSDL interface in a UDDI registry.

Understanding the Caller's Role

The caller is the financial management application that uses the currency conversion Web Service; the caller's role includes the following:

• Search UDDI Registry - The Web Service caller, the invoking business' enterprise application, searches the UDDI registry and locates the currency conversion service.

• Invoke the Currency Conversion Service - The invoking business invokes the currency conversion service using the information stored in the UDDI registry. This includes the URL for the service to locate the currency conversion service, and the WSDL interface to define the available methods in the currency conversion service.

• Communicate the Response - The caller and the Web Service communicate following a simple request/response pattern.