Web Services Interview Questions – Set 03

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What is WSDL?

The WSDL stands for Web Services Description Language. It is an XML document containing information about web services such as method name, method parameter. The Client needs a data dictionary which contains information about all the web services with methods names and parameters list to invoke them for the web services. The Web Service Description Language bridge up this gap, by providing all necessary information to the client.

Some Important elements used in Web Services Description language are as follows:

  • <message>: The message element in WSDL is used to define all different data elements for each operation performed by the web service.
  • <portType>: The port type element is used to determine the operation which can be performed by the web service. This operation can have two messages one is input and the second one is the output message.
  • <binding>: This element contains the used protocol.

Explain web service architecture?

The web service framework includes three different layers.

The roles of these layers are:

  • Service Provider: Role of Service provider is to make the web service which makes it accessible to the client applications over the Web.
  • Service Requestor: Service requestor refers to any consumer of web service like any client application. Client applications are written in any language contact web service for any functionality by sending XML request over the available network connection.
  • Service Registry: Service Registry is the centralized directory System which helps to locate the web services for client applications. Used to find the existing web services, as well as developers, can also create the brand new one web service also.
    The Service Provider uses the interface named as ?Publish? interface of Service Registry to make the existing web services available to client applications. With all the information provided by the service registry, service requestor able to find or invoke services.

What is the usage of WSDL in a web service?

WSDL is used in web service to describe the availability of service.

What is Interoperability in Web services?

The Web services facilitate various applications to communicate with each other and share data and services among themselves. Other applications can also use the web services. For example, a VB or .NET application can communicate with a Java web services and vice versa. Web services are used to make the application platform and technology independent.

How many Communication protocols can be used to implement a SOAP message? Is SOAP messages are tied to any protocol?

Communication protocol refers to the protocols which were used to transmit information over the web. By using Transport protocols, applications from the different background can quickly communicate with each other without knowing the inside functioning of the various systems. HTTP (Hyper-Text Transfer Protocol) can be used to implement a SOAP message whereas FTP (File Transfer Protocol) can be used as the reliable transport mechanism. SMTP and BEEP can also be used for transport mechanism.

SOAP message is not tied to any protocol. It can use any of the open Transport protocol.

What are the main features of web services?

Following is a list of main features of web services:

  • It is available over the Internet or private (intranet) networks.
  • It uses a standardized XML messaging system.
  • It is not tied to any one operating system or programming language.
  • It is self-describing via a common XML grammar.
  • It is discoverable via a simple find mechanism.

What is the usage of Service Discovery layer in Web Service Protocol Stack?

The Service Discovery layer is used for centralizing services into a universal registry and providing easy publish/find functionality.

Currently, service discovery is handled via Universal Description, Discovery, and Integration (UDDI).

What is UDDI?

The UDDI stands for Universal Description, Discovery and Integration. It is a XML based framework for describing, discovering and integrating web services. It contains a list of available web services. WSDL is the part of UDDI. More details..

What is XML-RPC?

The RPC is Remote Procedure Call. It is the method used for calling a procedure or function available on any remote computer on the web.

XML-RPC refers to a simple protocol used to perform RPCs by using XML messaging. It is an excellent tool for connecting different environments and also establishing connections between wide varieties of computers.

Explain the loosely coupled architecture of web services.

A consumer of a web service is not tied to that web service directly. The web service interface can change over time without compromising the client’s ability to interact with the service. A tightly coupled system implies that the client and server logic are closely tied to one another, implying that if one interface changes, the other must be updated. Adopting a loosely coupled architecture tends to make software systems more manageable and facilitates simpler integration between different systems.