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Distributed Technology:

Distributed technology is the concept of maintaining logic scattered on different systems. You can create applications, known as distributed applications, which can contain processing logic, such as accessing data from database server, using this technology.

these applications contain operations/functionalities/methods which encapsulates that logic and these methods are exposed in the internet so that other applications built using different technologies can even call those methods across machine boundary and receive desired data.

This concept provides 1) Reusability. 2) Better maintenance. 3) Security for certaion resources.

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•CORBA (Common Object Request Broker), APPC (Advanced Program-to-ProgramCommunications), RMI, DCOM, EDI were various technologies used in distributedapplications, but in all these technologies client and server are tightly coupled.

•With the advent of Web Services it was possible for applications which are looselycoupled and running on different platforms and written in different programmingcould integrate with each other.

Protocols – Language or medium of communication

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CORBA – Common Object Request Broker

RPC – Remote method calls

RMI – Remote Method Invocation

Vendor Specific – means the client or server had to follow the contract set by the technology

Eg : - IDL (Interface Definition Language) had to be used for communication in CORBA which left the Interface definition to the client who wanted to use a server

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Note: There are many Web services implementations that are not a service-oriented architecture. For example, the use of Web services to connect two heterogeneous systems directly together is not an SOA.

SOA are often associated with Web services and sometimes, SOA are even confusedwith Web services, but, SOA does not specifically mean Web services. Instead, Webservices can be seen as a specialized SOA implementation that incorporates the coreaspects of a service-oriented approach to architecture.

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•The Service Broker can be either public or private.

•Public Brokers are available all over the Internet.

•Private Brokers are available to limited audience (ex; users of a company wideIntranet)

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SOAP, WSDL and UDDI are XML based.

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The whole point of Web services is to enable applications developed in various platform and language work together, thereby increasing the overall performance of the organization.

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SOAP is independent of actual Web services implementation, thus it easily facilitatesinteroperability between Web services implementations on different platforms

SOAP is used for finding a service, publishing a service and binding to a service

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Web Services uses HTTP and SOAP to make business data available on the Web. It exposes the business objects (COM objects, Java Beans, etc.) to SOAP calls over HTTP and executes remote function calls. The Web Service consumers are able to invoke method calls on remote objects by using SOAP and HTTP over the Web.

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• WSDL provides a description for network services offered.

• WSDL is used to generate SOAP messages to access these service

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UDDI (Universal Description, Discovery and Integration) is an industry effort started in September 2000 by Ariba, IBM, Microsoft, and 33 other companies. Today, UDDI has over 200 community members.

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This slide demonstrates design-time usage:

1. .NET Developer builds and deploys a pricing web service

2. .NET Developer registers and categorizes the web service

3. Office VBA user queries UDDI for “pricing” services

4. Office VBA user determines the most appropriate “pricing” service

5. Office VBA user builds a solution that directly consumes the web service data

Note that once the Office VBA developer finds the service, UDDI is out of the picture. In this scenario, UDDI acts as a “match maker” and once the match is made, UDDI is no longer part of the client/server interaction.

Key Message(s):

Service-Oriented Architectures (SOAs) are composed of loosely coupled software services or components.

SOAs provide component isolation on a level where even the implementation language is hidden from service users, and focus on providing functionality as services.

SOAs utilize existing definitions for creating platform and implementation independent, inter-operative service networks.

SOA services can be interconnected through various technologies, although Web Services is the most common solution.

In Accenture, SOA has been identified as a significant architecture approach.

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Key Message(s):

SOAs leverage loosely coupled interfaces:

Traditional application integration design depends upon a tight interconnection of subsidiary elements, for example:

Programming language

Application server

Object model, and so forth

The complexity of these connections means that developers must thoroughly understand and have control over both ends of the connection. Once established, it is exceedingly difficult to extract one element and replace it with another.

Loosely coupled systems, on the other hand, require a much simpler level of coordination and allow for more flexible reconfiguration, which in turn allows an organization to quickly adapt to IT system changes.

SOAs use vendor-independent standards:

The development of generally open and accepted standards is a key strength of the coalitions that have been building Web Services infrastructure.

Most previous efforts at distributed computing, for example, Common Object Request Broker Architecture (CORBA), Distributed Component Object Model (DCOM), and Remote Method Invocation (RMI), were difficult to implement because they were dependent upon a particular vendor's product offering, were highly specified, or were programmatically complex; usually they were all three.

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Reference

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