- Interview 4 All

Q – 1 Explain SOAP?

Ans- SOAP is an XML-based protocol for exchanging information between computers. Although SOAP can be used in a variety of messaging systems and can be delivered via a variety of transport protocols, the main focus of SOAP is Remote Procedure Calls (RPC) transported via HTTP.

Like XML-RPC, SOAP is platform independent, and therefore enables diverse applications to communicate with one another.

Q – 2 What is UDDI?

Ans- UDDI (Universal Description, Discovery, and Integration) currently represents the discovery layer within the Web services protocol stack.

UDDI was originally created by Microsoft, IBM, and Ariba, and represents a technical specification for publishing and finding businesses and Web services.

At its core, UDDI consists of two parts.

UDDI is a technical specification for building a distributed directory of businesses and Web services. Data is stored within a specific XML format, and the UDDI specification includes API details for searching existing data and publishing new data.

Q – 3 Explain WSDL?

Ans- The Web Services Description Language (WSDL) currently represents the service description layer within the Web service protocol stack.

In a nutshell, WSDL is an XML grammar for specifying a public interface for a Web service.

This public interface can include the following:

Information on all publicly available functions.
Data type information for all XML messages.
Binding information about the specific transport protocol to be used.
Address information for locating the specified service.
WSDL is not necessarily tied to a specific XML messaging system, but it does include built-in extensions for describing SOAP services.

Q – 4 What knowledge needed for Web services client development?

Ans-

HTML: None, Web Services do not use HTML.
HTTP: How to type in a URL.
SOAP: None to minimal.
WSDL: None to minimal.
XML: None to considerable.

Q – 5 What knowledge needed for Web services publishing?

Ans-

HTML: None, Web Services do not use HTML.
HTTP: How to turn on the 4th Dimension Web server.
SOAP: How to activate 4th Dimension Web Services.
WSDL: None to minimal.
XML: None.

Q – 6 Are Web services new?

Ans- Yes and no. The SOAP and WSDL standards are relatively new, but the idea of sending messages between programs over a network has been around for decades.

Past efforts to create network-oriented distributed object frameworks like CORBA, DCOM, and Java RMI haven’t gone to waste. While creating these tools, the computer science and application development communities discovered and learned important information about how to build widely distributed systems. In the words of Tim Bray, co-editor of the XML 1.0 spec:

SOAP has the advantages that it’s simpler and easier to implement than any existing alternative, and makes better use of the pervasive Web infrastructure. The effect is that you can pull a system together using SOAP in weeks, not quarters.

Obviously, the alternatives offer richer feature sets, particularly in the area of transaction semantics, security, and so on, but at a dramatically higher cost. SOAP will not sweep all before it; but it will be very widely deployed across the Internet and the intranets of this world.

Q – 7 Why are Web services so fashionable?

Ans- Today’s variety of computer platforms, operating systems, programming languages, and development environments shows no signs of diminishing. Heterogeneity is the norm in the IT world, has always been so, and will remain so for the foreseeable future.

Getting diverse systems to communicate and cooperate is an ongoing challenge for many organizations. Past efforts to create an overall framework for network-oriented program integration, such as DCOM and CORBA, are complex, proprietary, and expensive to implement.

Reducing the cost and complexity of integration projects is a driving force behind Web Services standardization and adoption. While current Web Service systems have fewer features than a system like CORBA, today’s Web Services offer more features than developers actually need.

Fortunately, the largest software vendors in the world, including- Microsoft, IBM, Sun, and Oracle-are cooperating on the core Web Service standards. 4th Dimension’s Web Services features enable developers to quickly and easily publish and subscribe to Web Services.

Q – 8 Explain XML-RPC?

Ans- XML-RPC 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.

More succinctly, XML-RPC = HTTP + XML + Remote Procedure Calls.
Because XML-RPC is platform independent, diverse applications can communicate with one another. For example, a Java client can speak XML-RPC to a Perl server.
To get a quick sense of XML-RPC, here is a sample XML-RPC request to a weather service (with the HTTP Headers omitted):
weather.getWeather
10016
The request consists of a simple element, which specifies the method name (getWeather) and any method parameters (zip code).

Here is a sample XML-RPC response from the weather service:

The response consists of a single element, which specifies the return value (the current temperature). In this case, the return value is specified as an integer.
In many ways, XML-RPC is much simpler than SOAP, and therefore represents the easiest way to get started with Web services.
The official XML-RPC specification is available at XML-RPC.com. Dozens of XML-RPC implementations are available in Perl, Python, Java, and Ruby. See the XML-RPC home page for a complete list of implementations.

Q – 9 What is service discovery Web service protocol stack layer?

Ans- This layer is responsible for centralizing services into a common registry, and providing easy publish/find functionality. Currently, service discovery is handled via the UDDI.

Beyond the essentials of XML-RPC, SOAP, WSDL, and UDDI, the Web service protocol stack includes a whole zoo of newer, evolving protocols. These include WSFL (Web Services Flow Language), SOAP-DSIG (SOAP Security Extensions: Digital Signature), and USML (UDDI Search Markup Language). For an overview of these protocols.

Q – 10 What is service description Web service protocol stack layer?

Ans- This layer is responsible for describing the public interface to a specific Web service. Currently, service description is handled via the WSDL.

Q – 11 What is XML messaging Web service protocol stack layer?

Ans- This layer is responsible for encoding messages in a common XML format so that messages can be understood at either end. Currently, this includes XML-RPC and SOAP.

Q – 12 What is service transport Web service protocol stack layer?

Ans- This layer is responsible for transporting messages between applications. Currently, this includes HTTP, SMTP, FTP, and newer protocols, such as Blocks Extensible Exchange Protocol (BEEP).

Q – 13 Define Web service protocol stack?

Ans- The Web service protocol stack is an evolving set of protocols used to define, discover, and implement Web services.

The core protocol stack consists of four layers:

★ Service Transport
★ XML Messaging
★ Service Discovery
★ Service Description

Q – 14 What is new about Web services?

Ans- People have been using Remote Procedure Calls (RPC) for some time now, and they long ago discovered how to send such calls over HTTP.
So, what is really new about Web services? The answer is XML.

XML lies at the core of Web services, and provides a common language for describing Remote Procedure Calls, Web services, and Web service directories.

Prior to XML, one could share data among different applications, but XML makes this so much easier to do. In the same vein, one can share services and code without Web services, but XML makes it easier to do these as well.

By standardizing on XML, different applications can more easily talk to one another, and this makes software a whole lot more interesting.

Q – 15 Define Web services?

Ans- Many people and companies have debated the exact definition of Web services. At a minimum, however, a Web service is any piece of software that makes itself available over the Internet and uses a standardized XML messaging system.

First, a Web service can have a public interface, defined in a common XML grammar. The interface describes all the methods available to clients and specifies the signature for each method. Currently, interface definition is accomplished via the Web Service Description Language (WSDL).

XML is used to encode all communications to a Web service. For example, a client invokes a Web service by sending an XML message, then waits for a corresponding XML response. Because all communication is in XML, Web services are not tied to any one operating system or programming language-Java can talk with Perl; Windows applications can talk with Unix applications.

Second, if you create a Web service, there should be some relatively simple mechanism for you to publish this fact. Likewise, there should be some simple mechanism for interested parties to locate the service and locate its public interface. The most prominent directory of Web services is currently available via UDDI, or Universal Description, Discovery, and Integration.

Q – 16 Tell me which tool installs DLL on local computer and installs the Windows service in transactional manner?

Ans- The Installutil.exe tool.

Q – 17 Tell me which namespace must be included in a code that enables XML Web service to write events in an event log file?

Ans- The System.Diagnostics is the namespace, which must be included in a code to enable a Web service for writing events in an event log file.

Q – 18 What is the name of the directory where it is necessary to locate the proxy file to use a Web service?

Ans- The proxy file must be stored in the /bin directory. This directory is situated under the root directory of the application.

Q – 19 Tell me does a Web service have state?

Ans- The Web services do not have any technique to maintain state. However, it can access ASP.NET objects, such as application and session if they extend from the WebService base class.

Q – 20 Describe the use of a .disco file?

Ans- A client application uses a .disco file to locate or discover the documents that contain the description of a Web service. The .disco file contains links to other resources, which describe essential features, such as capabilities of a Web service. The links contained in a .disco file can refer to other discovery documents or XSD schemas.

The description about the services and capabilities of a Web service is written in Web services Description Language (WSDL). A .disco file can also contain the information about other XML Web services that reside on the same or a different Web server.

Q – 21 Explain SOAP encoding?

Ans- The Serialization of the types, such as integers and strings, inside a SOAP message is called encoding. The SOAP objects use XML elements and attributes to serialized data, for example, encodingStyle is an attribute of the Envelop element, which is used to specify the encoding rules for a SOAP object.

Q – 22 Listed the names of public properties defined in the WebService class?

Ans- There are many properties defined in the WebServices class:

★ Application – Obtains the application object for the current HTTP request
★ Context – Obtains the HttpContext object for the current request, which encapsulates all HTTP-specific context used by the HTTP server to process Web requests
★ Server – Obtains the HttpServerUtility object for the current request
★ Session – Obtains the HttpSessionState object for the current request
★ SoapVersion – Obtains the version of the SOAP protocol used to make the SOAP request to a Web service
★ User – Obtains the Server User Object. This property can be used to authenticate whether a user is authorized to execute the request.

Q – 23 Tell me which property of the WebMethod attribute allows you to maintain the state of objects across sessions in a Web method?

Ans- The WebMethod attribute’s EnableSession property enables you to enable session state for a Web method.

Q – 24 Tell me which step is necessary to perform before a Web service can be consumed?

Ans- It is necessary to build a proxy class by using the wsdl.exe utility before a Web service can be consumed.

Q – 25 Tell me which two methods are used to discover the URL of Web services?

Ans- The two methods to discover the URL of Web services are:

★ Web service discovery tool (Disco.exe)
★ UDDI.

Q – 26 Described about DISCO?

Ans- DISCO is a technology developed by Microsoft to publish and discover Web services. It discovers URLs of all XML Web services located on a Web server and creates a list of these Web services in a file called as a DISCO file.

Q – 27 What portType element of a WSDL document contain?

Ans- The portType element contains the operations exposed by the Web service, and the messages involved in the communication between the Web service and its consumers.

Q – 28 What namespace is must import in code to build a Web service?

Ans- System.Web.Services is the elementary namespace, which must be imported to develop code of a Web service.

Q – 29 List the advantages that Web services have over COM (Component Object Model)and DCOM (Distributed Component Object Model)?

Ans- The advantages of Web services over COM and DCOM are as follows:

★ Web services are simple to use and can be implemented on varied platforms.
★ Web services are loosely coupled; as a result, their interfaces and methods can be extended.
★ Web services do not carry any state information with them so that multiple requests can be processed simultaneously.

Q – 30 Define the concept of Web services briefly?

Ans- A Web service may be defined as an independent and self-sustained unit of a software application that is hosted on the Web and implement specific functionalities to execute the business logic.

A Web service provides so many functionalities, such as generating pay slips for employees, computing tax, broadcasting weather report, and providing updated news. The Web service allows application to share information or exchange data with other applications across different operating systems and hardware.

Therefore, the work of a Web service is to unite software by exchanging data irrespective of their operating systems, supported hardware, and programming language used in their development.

The Web services transfer data in the XML format and use Simple Object Access Protocol (SOAP) to communicate. It is an XML based protocol. The Web services use Web Services Description Language (WSDL) and Universal Description, Discovery, and Integration (UDDI) to describe itself.

Q – 31 How to prevent Web services from unauthorized access?

Ans- The following are the ways to prevent your Web service from unauthorized access:

★ Using encryption and message-based security.
★ Using authentication and access controls for the Web service.

Q – 32 Explain EventLog class?

Ans- The EventLog class is used to access the Windows event logs from Windows services. Using EventLog, you can also customize Windows event logs that record information about important software and hardware events, such as the events of the .NET controls, keyboard, or other hardware devices.

The EventLog class allows you to read or write to event logs, delete logs, and create as well as delete event sources. You can use the EventLog class to create event logs while creating an event source. An event source can be used to write to only one event log at a particular time. However, it is possible to associate one event log to multiple sources.

Q – 33 How to ensure that only authorized users access web service?

Ans- You should use the element to ensure that only authorized users access your Web service. This element allows or denies access to your Web service according to their role.

Q – 34 Describe the advantage that UDDI has over DISCO?

Ans- The UDDI directory has an advantage over a DISCO file, as it provides a single location where a client can find the Web services offered by different organizations.

Q – 35 What elements are contained in the WSDL document?

Ans-

★ Types – Describe the variations of data types that are used to exchange messages between the user and the provider.
★ Message – Describes the actual message or method call.
★ PortType – Describes the set of operations and each related message.
★ Binding – Describes the protocol details.
★ Service – Used to make groups a set of related ports together.

Q – 36 Define WSDL?

Ans- WSDL is a short form for Web Services Description Language, which is used to describe a Web service in terms of the messages that it creates and accepts. The WSDL document is an XML file that contains the interface schema for the Web service. It identifies the methods that are used during the exchange between a Web service consumer and a Web service provider.

Q – 37 What is the use of the mustUnderstand attribute in the Header element of a SOAP message?

Ans- The mustUnderstand attribute indicates that a header entry is either required or optional for the recipient to process further.

Q – 38 What is the file extension for a Web service?

Ans- A Web service file extension is .asm file. For example, service1.asmx is a Web service file.

Q – 39 Define the services that UDDI provides to Web applications?

Ans- UDDI provides the following types of services to a Web application:

★ XML Schema for business descriptions – Includes information about the service publisher (contact name, address, and so on) and specifications on the Web service
★ Web registry of Web services – Includes business, service, and binding information for the Web service

Q – 40 Explain windows services?

Ans- Windows services are previously known as NT services, are applications that are installed on the system as system services. In other words, Windows services are applications that run in the background with the Windows operating system.

The primary use of Windows services is to reduce the consumption of memory required for performing backend operations. Let’s take an example to understand this easily. Suppose you want to perform a variety of functions, such as monitor the performance of your computer or application, check the status of an application, and manage various devices, such as printers.

In such a case, you can use Windows services to reduce memory consumption. In addition, Windows services can run on your system even if you have not logged on to your computer. In addition, these services do not have any user interface.

Q – 41 Can we share a process between windows services?

Ans- Yes, you can share a process between Windows services.

Q – 42 Which is the parent class to create all windows services in .NET?

Ans- The ServiceBase class is the parent class to create all Windows services.

Q – 43 Tell me what class in .NET is used to install a Windows service?

Ans- The ServiceInstaller class, also known as the project installer class, is used to install a Windows service.

Q – 44 What class in .NET is used to install a Windows service?

Ans- The ServiceInstaller class, also known as the project installer class, is used to install a Windows service.

Q – 45 Is it true that while installing a Windows service, an EventLogInstaller class is automatically created to install the event log related to the particular service?

Ans- Yes, it’s true.

Q – 46 Tell me which property of the ServiceBase class can be used to specify whether a service can be paused and resumed?

Ans- The CanPauseAndContinue property provides such type of service.

Q – 47 Does the W3C support any Web service standards?

Ans- The World Wide Web Consortium (W3C) is actively pursuing standardization of Web service protocols. In September 2000, the W3C established an XML Protocol Activity. The goal of the group is to establish a formal standard for SOAP. A draft version of SOAP 1.2 is currently under review, and progressing through the official W3C recommendation process.

On January 25, 2002, the W3C also announced the formation of a Web Service Activity. This new activity will include the current SOAP work as well as two new groups.

The first new group is the Web Services Description Working Group, which will take up work on WSDL. The second new group is the Web Services Architecture Working Group, which will attempt to create a cohesive framework for Web service protocols.

Q – 48 How do I get started with Web Services?

Ans- The easiest way to get started with Web services is to learn XML-RPC. Check out the XML-RPC specification or read my book, Web Services Essentials. O’Reilly has also recently released a book on Programming Web Services with XML-RPC by Simon St.Laurent, Joe Johnston, and Edd Dumbill.

Once you have learned the basics of XML-RPC, move onto SOAP, WSDL, and UDDI. These topics are also covered in Web Services Essentials. For a comprehensive treatment of SOAP, check out O’Reilly’s Programming Web Services with SOAP, by Doug Tidwell, James Snell, and Pavel Kulchenko.

Q – 49 What is UDDI?

Ans- UDDI (Universal Description, Discovery, and Integration) currently represents the discovery layer within the Web services protocol stack.

UDDI was originally created by Microsoft, IBM, and Ariba, and represents a technical specification for publishing and finding businesses and Web services.

At its core, UDDI consists of two parts.
First, UDDI is a technical specification for building a distributed directory of businesses and Web services. Data is stored within a specific XML format, and the UDDI specification includes API details for searching existing data and publishing new data.

Second, the UDDI Business Registry is a fully operational implementation of the UDDI specification. Launched in May 2001 by Microsoft and IBM, the UDDI registry now enables anyone to search existing UDDI data. It also enables any company to register themselves and their services.

The data captured within UDDI is divided into three main categories:

White Pages:

This includes general information about a specific company. For example, business name, business description, and address.

Yellow Pages:

This includes general classification data for either the company or the service offered. For example, this data may include industry, product, or geographic codes based on standard taxonomies.

Q – 50 What is WSDL?

Ans- The Web Services Description Language (WSDL) currently represents the service description layer within the Web service protocol stack.

In a nutshell, WSDL is an XML grammar for specifying a public interface for a Web service.

This public interface can include the following:

WSDL is not necessarily tied to a specific XML messaging system, but it does include built-in extensions for describing SOAP services.

Below is a sample WSDL file. This file describes the public interface for the weather service used in the SOAP example above. Obviously, there are many details to understanding the example. For now, just consider two points.

First, the elements specify the individual XML messages that are transferred between computers. In this case, we have a getWeatherRequest and a getWeatherResponse. Second, the element specifies that the service is available via SOAP and is available at a specific URL.

Q – 51 What is SOAP?

To get a quick sense of SOAP, here is a sample SOAP request to a weather service (with the HTTP Headers omitted):

<ns1:getWeather
xmlns:ns1=”urn:examples:weatherservice”
SOAP-ENV:encodingStyle=” http://www.w3.org/2001/09/soap-encoding
10016

Q – 52 What is XML-RPC?

Because XML-RPC is platform independent, diverse applications can communicate with one another. For example, a Java client can speak XML-RPC to a Perl server.

To get a quick sense of XML-RPC, here is a sample XML-RPC request to a weather service (with the HTTP Headers omitted):

weather.getWeather
10016
The request consists of a simple element, which specifies the method name (getWeather) and any method parameters (zip code).

Q – 53 What is the Web service protocol stack?

Ans- The Web service protocol stack is an evolving set of protocols used to define, discover, and implement Web services. The core protocol stack consists of four layers:

Service Transport:

This layer is responsible for transporting messages between applications. Currently, this 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 understood at either end. Currently, this includes XML-RPC and SOAP.

Service Description:

This layer is responsible for describing the public interface to a specific Web service. Currently, service description is handled via the WSDL.

Service Discovery:

This layer is responsible for centralizing services into a common registry, and providing easy publish/find functionality. Currently, service discovery is handled via the UDDI.

Q – 54 I keep reading about Web services, but I have never actually seen one. Can you show me a real Web service in action?

Ans- If you want a more intuitive feel for Web services, try out the IBM Web Services Browser, available on the IBM Alphaworks site. The browser provides a series of Web services demonstrations. Behind the scenes, it ties together SOAP, WSDL, and UDDI to provide a simple plug-and-play interface for finding and invoking Web services.

For example, you can find a stock-quote service, a traffic-report service, and a weather service. Each service is independent, and you can stack services like building blocks. You can, therefore, create a single page that displays multiple services–where the end result looks like a stripped-down version of my.yahoo or my.excite.

Q – 55 What is new about Web services?

XML lies at the core of Web services, and provides a common language for describing Remote Procedure Calls, Web services, and Web service directories.

By standardizing on XML, different applications can more easily talk to one another, and this makes software a whole lot more interesting.

Q – 56 What is a Web service?

XML is used to encode all communications to a Web service. For example, a client invokes a Web service by sending an XML message, then waits for a corresponding XML response. Because all communication is in XML, Web services are not tied to any one operating system or programming language–Java can talk with Perl; Windows applications can talk with Unix applications.

Beyond this basic definition, a Web service may also have two additional (and desirable) properties:

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