The Validity Of Describing Web Services As A Poor Man'S Distributed Object Technology

Introduction:

Middleware has undergone an evolution, from being procedural to object oriented to component based. Emerging web services is considered to be a new evolution in middleware platforms because they are built on web standards that are extensively adapted to sharing information. Recently, however, web services middleware has been described as a poor man's distributed middleware because it provides a similar service to other middleware technologies with high degree of performance.

In this essay I will discuss the services offered by web services technology and compare them to other middleware services in order to present a clear validation for that claim.

The following discussion will begin with an overview of web services. This will include web services architecture roles and standards. Then I will concentrate on web services technology to compare it with other middleware .This will focus on: service description, service discovery and registry, WS* standards, interaction styles and separation interfaces and implementation. This will be followed by a look at service composition and interoperability. After that, I will examine the performance of middleware in order to determine the differences in performance between web services, CORBA, Java RMI and DCOM. Finally, I will conclude my discussion by summarizing the main aspects related to this claim in order to determine its validity.

1- Overview of web services:

With increasing interest from the web, web services have emerged to support software interactions over the Internet. Cerami [2002] states that web services architecture mainly depends on three major roles and is built on standards protocols that are widely adopted and play an important role in hiding the heterogeneity problems.

1.1 Web services roles:

In web services, interactions between services or applications demand three important roles: firstly, a service provider, which is responsible for transforming functionality to services in order to respond to local or external calls [Cerami, 2002]. Secondly, a service requester, that sends an invocation in XML (Extensible Markup Language) style to the service provider when it knows its address. The service requester could be another service or users or other applications that need service [Cerami, 2002].. Finally, a service registry is, as defined by Cerami [2002], a place where developers publish their services by storing WSDL files, then users or service requesters search for services to interact with after gaining their URL addresses.

1.2 Web services standards:

There are three important standards in web services, which are WSDL (Web Services Definition Language), SOAP (Simple Object Access Protocol) and UDDI (Universal Description, Discovery and Integration). These standards are developed to transport and transform business data more effectively over the Internet,