What are Web Services?

Web services are client and server applications that communicate over the Hyper Text Transfer Protocol (HTTP). As described by W3C, web services provide a standard means of interoperating between software applications running on a variety of platforms and frameworks. Web services are characterized by their great interoperability and extensibility as well as their machine-processable descriptions. Web services can be combined in a loosely coupled way to achieve complex operations. Programs providing simple services can interact with each other to deliver sophisticated added-value services.

A key feature of web services is that applications can be written in various languages and are still able to communicate by exchanging data with one another via a web service between clients and servers. A client summons a web service by sending a request via XML over HTTP, and the service then responds with an XML response. Web services are also often associated with SOA (Service-Oriented Architecture).

A web service supports communication among numerous apps with HTML, XML, WSDL, SOAP, and other open standards. XML tags the data, SOAP (Simple Object Access Protocol) transfers the message, and WSDL (Web Services Description Language) describes the service’s accessibility.

Ability to support Remote Procedure Calls (RPCs) — Web services enable clients to invoke procedures, functions, and methods on remote objects using an XML-based protocol. Remote procedures expose input and output parameters that a web service must support.

Synchronous or Asynchronous functionality- Synchronicity refers to the binding of the client to the execution of the service. In synchronous operations, the client will wait for the web service to complete an operation. An example of this is probably a scenario wherein a database read and write operation are being performed. If data is read from one database and subsequently written to another, then the operations have to be done in a sequential manner. Asynchronous operations allow a client to invoke a service and then execute other functions in parallel. This is one of the common and probably the most preferred techniques for ensuring that other services are not stopped when a particular operation is being carried out.