Question 361 – What is a WSDL?

• WSDL is an XML-based language for describing Web services and how to access them.
• WSDL stands for Web Services Description Language
• WSDL is written in XML
• WSDL is an XML document
• WSDL is used to describe Web services
• WSDL is also used to locate Web services
• WSDL is a W3C recommendation
• A .wsdl file is an XML document written in an XML grammar.
• It defines how an XML Web service behaves and instructs clients as to how to interact with service.

Question 362 – What are the elements of WSDL?

Below are the elements that are mainly used in WSDL.

<types>    The data types used by the web service
<message>    The messages used by the web service
<portType>    The operations performed by the web service
<binding>    The communication protocols used by the web service

Question 363 – What is a DISCO?

• DISCO is Discovery of Web Services
• It’s a document, which typically resides at the root of the web server.
• Contains references to the location of available web services. 
• It allows the discovery of services at a known URL.
• It can define a document format along with an interrogation algorithm, making it possible to discover the Web Services exposed on a given server.
• It is the discovery file which gives path to the Webservices
• It contains WSDL When one searches for Web Services, it will go to the DISCO which gives actual info
  Disco.exe – The Web Services Discovery tool discovers URLs of XML Web services located on a Web server and saves documents related to each XML web service on local disk. Syntax – disco [options] URL

Question 364 – What is a VSDISCO?

• VSDISCO files are DISCO files that support dynamic discovery of Web services.
• ASP.NET links the VSDISCO to a HTTP handler that scans the host directory and subdirectories for ASMX and DISCO files and returns a dynamically generated DISCO document.
• A client who requests a VSDISCO file gets back what appears to be a static DISCO document.
• Microsoft is actively discouraging the use of VSDISCO files because they could represent a threat to Web server security.
• VSDISCO files are disabled in the release version of ASP.NET. We can reenable them by uncommenting the line in the <httpHandlers> section of Machine.config

Question 365 – What are the different Protocols in webservice?

• 3 Different protocols can be used such as Http-Get, Http-Post, and SOAP.
• These protocols are included in the WSDL file that is automatically generated in .NET application.
• It is preferable to use Http-Get and Http-Post only when name/value pairs of data is available

Question 366 – What are the component we get while Deploying Webservice?

• Web application directory
• web.config file
• .asmx files
• .disco files
• Bin folder( containing dlls)
• Keep alive ( for load balancing)

Question 367 – What is a Webservice protocol stack?

• It is a set of protocols used to define, discover, and implement WS.
• The protocol stack consists of 4 layers as follows
• Service Transport: This layer is responsible for transferring messages between different applications. It includes HTTP, SMTP, FTP, and newer protocols such as Blocks Extensible Exchange Protocol (BEEP).
• XML Messaging: This layer is responsible for encoding messages in a common XML format so that messages can be understand at either end. It includes XML-RPC and SOAP.
• Service Description: This layer is responsible for describing the public interface to a specific Web service. This service description is handled via the WSDL.
• Service Discovery: This layer is responsible for centralizing services into a common registry, and providing easy functionality. This service discovery is handled via the UDDI.

Question 368 – What is a XML-RPC?

• It is a protocol that uses XML messages to perform Remote Procedure Calls.
• Requests are encoded in XML and sent via HTTP POST;
• XML responses are embedded in the body of the HTTP response.
• XML-RPC = HTTP + XML + Remote Procedure Calls.
• It is platform independent, so diverse applications can communicate with one another.
• For example, a Java client can speak XML-RPC to a Perl server.

Question 369 – What is a Secure Webservices?

• If we need to encrypt the data exchange, you use Secure Sockets Layer (SSL) or a Virtual Private Network to keep the bits secure.
• For authentication, use HTTP Basic or Digest authentication with Microsoft® Windows® integration to figure out who the caller is.

Question 370 – Checklist for Webservice Performance

• Reduce round trips.
• Prefer message-based programming over remote procedure call (RPC) style.
• Use primitive types for Web service parameters.
• Avoid server state between calls.
• Provide input validation for costly Web methods.
• Check the caching options.
• Check for bulk data transfer and attachments.
• Avoid calling local Web Services.
• Use asynchronous Web methods for I/O operations.
• Do not use asynchronous Web methods when you depend on worker threads.
• Consider calling Web services asynchronously when you have additional parallel work.
• Use asynchronous invocation to call multiple unrelated Web services.
• Call Web services asynchronously for UI responsiveness.
• Set your proxy timeout appropriately.
• Set your ASP.NET timeout greater than your Web service timeout.
• Enable session state only for Web methods that need it.
• Reduce serialization with XmlIgnore.
• Reduce round trips.
• Consider XML compression.

Disclaimer – F5debug Interview Questions & Answers Series:

You may recopy extracts from these pages ("the material") to individual third party websites or to any intranet websites, but only if:
You acknowledge www.f5debug.net as the source of the material. Such acknowledgment should include reference to www.f5debug.net in the copy of the material and should also include “© Karthikeyan Anbarasan, www.f5debug.net ". You inform the third party that these conditions apply to him/her and that he/she must comply with them.