Why do we need .Net Web Services?

We have a number of heterogeneous technologies available on internet. The demand for reusable components across platforms and programming languages are high. Most of the components have the limitation that they can't share or exchange data across different platforms, they are mostly language specific or platform specific. The technologies like COM, RMI, CORBA etc. contributed best to fulfill requirements to some extent, but components result from these said technologies are mostly either language specific or platform specific.

To avoid above problem, we need to have web services. Through web services we have overcome the problem of interoperability between languages and platforms. Web services uses SOAP as transport protocol which uses a text based messaging model, i.e. XML to communicate between disparate systems.

Deploying a Web Service

Deploying the .Net Web Services is as simple as any ASP.NET application. Similar to ASP.NET applications, you need to copy or upload the .ASMX file and the .DISCO files to the appropriate directories, and that's it.

Explain in brief different distributed technologies.

The need of distributed technologies arises with the requirement of distributed computing applications. The distributed computing allows partitioning of application logic into units and spreading the unit over different computers of a network or across different networks. This helps in spreading out loads over many computers. The components once developed can be reuse by other applications. There are many technologies developed to allow the distribution and reuse of application logic.

Advantages of the distributed components:

• The key benefit of having distributed components is that they spread out the load over different machines.
• The components can be upgraded without disturbing the clients' code.
• The distributed application improves security. For example, a company who has many agents wouldn’t like those agents to have direct access to its database. Instead, these agents can be granted access to the components running on the corporate server which can be controlled and restricted.

Web services vs. CORBA and DCOM.

Web services
Web services use HTTP protocol for sending and receiving messages between the applications.
The data encoding in web services is based on XML.
Web services are defined using WSDL (Web Services Description Language).

• Web services are discovered using UDDI (Universal Description, Discovery and Integration).
• Web services are firewalls friendly.
• Web services supports interoperability i.e. cross platform integration is possible.

CORBA and DCOM

• These technologies use non-standard protocol, i.e. CORBA uses IIOP (Inter Internet Object Protocol), and DCOM uses RPC (Remote Procedure Calls)
• CORBA components are defined using CORBA Interface Description Language; DCOM components are defined using Microsoft Interface definition languages
• CORBA components are discovered using the CORBA registry, DCOM using the Registry.
• DCOM is a proprietary protocol that does not support interoperability and has firewall problems as DCOM transfers data in binary format and it uses many ports to call remote functions.
• CORBA uses the IIOP protocol, which is non-Internet friendly.
• CORBA and DCOM are fine for building enterprise applications that runs on the same platform and not good enough for applications that span platforms and languages.