Why Web Services ?

Overview

Component-based programming is more popular than ever. Almost no application is built today and does not involve the use of some form of the component, usually from a different vendor. As applications become more complex, the need to utilize components distributed across remote machines is growing.

An example of a component-based application is an end-to-end e-commerce solution. An e-commerce application residing on a web farm needs to submit an order to a back-end enterprise resource planning (ERP) application. In many cases, ERP applications reside on different hardware and may run on different operating systems.

The Microsoft Distributed Component Object Model (DCOM) is a distributed object infrastructure that allows applications to invoke Component Object Model (COM) components installed on another server and has been ported to many non-Windows platforms. But DCOM has never been widely recognized on these platforms and is rarely used to facilitate communication between Windows and non-Windows computers. ERP software vendors often create components for the Windows platform to communicate with back-end systems through proprietary protocols.

Some of the services utilized by e-commerce applications may not be in the data center at all. For example, if an e-commerce application accepts a credit card payment for a product purchased by a customer, it must take the merchant bank's service to process the customer's credit card information. But for all practical purposes, DCOM and related technologies (such as CORBA and Java RMI) are limited to applications and components installed in enterprise data centers. The two main reasons for doing this are that by default these technologies utilize proprietary protocols and that these protocols are essentially connection oriented.

Clients that communicate with servers over the Internet face many potential obstacles to communicating with servers. Security-aware network administrators around the world have implemented enterprise routers and firewalls that allow almost no type of communication over the Internet. It is often necessary for God's behavior to allow network administrators to open ports that are beyond the minimum.

If you are fortunate enough to have the network administrator open the appropriate port to support your service, your customers are probably not so lucky. Therefore, the proprietary protocols used by DCOM, CORBA, and Java RMI are not practical for Internet solutions.

As I said, another problem with using these technologies is that they are connection-oriented in nature and therefore cannot handle network interruption gracefully. Since the Internet is not under your direct control, you cannot make any assumptions about the quality or reliability of the connection. If a network outage occurs, the client's next call to the server may fail.

The connection-oriented nature of these technologies also makes it challenging to build a load-balanced infrastructure necessary to achieve high scalability. Once the connection between the client and server is broken, you cannot simply route the next request to another server.

Developers try to overcome these limitations by exploiting a model called stateless programming, but their success is limited because these techniques are quite cumbersome and make rebuilding connections to remote objects expensive.

Because the processing of customer credit cards is done by remote servers on the Internet, DCOM is not ideal for facilitating communication between e-commerce clients and credit card processing servers. As with ERP solutions, third-party components are typically installed in the client's data center (in this case, by a credit card processing solution provider). This component is only used as a proxy to facilitate communication between e-commerce software and merchant banks through proprietary protocols.

Do you see a pattern here? Due to the limitations of prior art in facilitating communication between computer systems, software vendors often employ their own infrastructure. This means that resources that can be used to add improved functionality to an ERP system or credit card processing system have been specifically written for proprietary network protocols.

To better support such Internet solutions, Microsoft initially adopted a strategy to enhance its existing technology, including COM Internet Services (CIS), which allows you to establish a DCOM connection between the client and remote components over port 80. The reason is that CIS is not widely accepted.

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