XML Interview Questions and Answers

What is XSL?
XSL (the extensible Style sheet Language) is used to transform XML document to some other document. So its transformation document which can convert XML to some other document. For instance you can apply XSL to XML and convert it to HTML document or probably CSV files.
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What is XML?
XML stands for extensible markup language much like as a HTML. XML was designed to carry data, not to display data. XML loosely couples disparate applications or systems utilizing JMS, Web services etc. XML uses the same building blocks that HTML does: elements attributes and values. XML tags are not predefined. You must define your own tags.
Why is XML important?

Scalable: Since XML is not in a binary format you can create and edit files with anything and it's also easy to debug. XML can be used to efficiently store small amounts of data like configuration files (web.xml, application.xml, strutsconfig. xml etc) to large company wide data with the help of XML stored in the database. 
Fast Access: XML documents benefit from their hierarchical structure. Hierarchical structures are generally faster to access because you can drill down to the section you are interested in. 
Easy to identify and use: XML not only displays the data but also tells you what kind of data you have. The mark up tags identifies and groups the information so that different information can be identified by different application. 
Style ability: XML is style-free and whenever different styles of output are required the same XML can be used with different style-sheets (XSL) to produce output in XHTML, PDF, TEXT, another XML format etc. 
Linkability, in-line usability, universally accepted standard with free/inexpensive tools

Describe the differences between XML and HTML?

XML HTML
designed to transport and store data, with focus on what data is designed to display data, with focus on how data looks
User definable tags Defined set of tags designed for web display
Content driven Format driven
End tags required for well formed documents End tags not required
Quotes required around attributes values Quotes not required
Slash required in empty tags Slash not required

 

Is XML meant to replace HTML?

No, they both go together one is for describing data while other is for displaying data.

What is CDATA section in XML?

All data is normally parsed in XML but if you want to exclude some elements you will need to put those elements in CDATA.

Is XML case sensitive?
XML tags are case sensitive. The tag is different from the tag .

What is DOM?
A DOM (Document Object Model) defines a standard way for accessing and manipulating documents. The XML DOM defines a standard way for accessing and manipulating XML documents. The XML DOM views an XML document as a tree-structure. All elements can be accessed through the DOM tree. Their content (text and attributes) can be modified or deleted, and new elements can be created. The elements, their text, and their attributes are all known as nodes.
Define DTD (Document Type definition)?
DTD - Document Type Definition defines the legal building blocks of an XML document. It defines the document structure with a list of legal elements and attributes. XML DTD is a rule book that an XML document follows. Once DTD is ready, you can create number of XML documents following the same rules specified in the DTD. DTD can be internal or external DTD. The internal DTD is included in the XML document, while external DTD exists outside the content of the documents.
Explain DTD and schema?

A DTD provides a list of the elements, attributes, comments, notes, and entities contained in an XML or HTML document and indicate their relationship with each other. 

DTD supports two types of data - CDATA and PCDATA.
Schema means the organization and the structure of a database. Schema supports numeric, Boolean and String data types and suitable for applications that developed in a programming language. Schema supports custom data types. Schema supports encapsulation and inheritance concepts. Schema supports for WEB services, XSLT.

E.g.: An XML schema is a description of XML document. It is expressed in terms of constraints on the structure and content of documents.

What are the standard ways of parsing XML document? or What is a XML parser?

XML parser sits in between the XML document and the application who want to use the XML document. Parser exposes set of well defined interfaces which can be used by the application for adding, modifying and deleting the XML document contents. 

There are two standard specifications which are very common and should be followed by a XML parser:- 

DOM: - Document Object Model.
IT is an open standard. The XML file is arranged in a tree fashion. DOM supports random access to the data of XML file. 
DOM is a W3C recommended way for treating XML documents. In DOM we load entire XML document into memory and allows us to manipulate the structure and data of XML document. 

SAX: - Simple API for XML. 
SAX is event driven way for processing XML documents. In DOM we load the whole XML document in to memory and then application manipulates the XML document. But this is not always the best way to process large XML documents which have huge data elements. For instance you only want one element from the whole XML document or you only want to see if the XML is proper which means loading the whole XML in memory will be quiet resource intensive. SAX parsers parse the XML document sequentially and emit events like start and end of the document, elements, text content etc. So applications who are interested in processing these events can register implementations of callback interfaces. 
SAX parser then only sends those event messages which the application has demanded. 

In What scenarios will you use a DOM parser and SAX parser?

If we do not need all the data from the XML file then SAX approach is much preferred than DOM as DOM can quiet memory intensive. In short if you need large portion of the XML document its better to have DOM. 
With SAX parser you have to write more code than DOM. 
If we want to write the XML in to a file DOM is the efficient way to do it. 
Some time you only need to validate the XML structure and do not want to retrieve any Data for those instances SAX is the right approach. 

Define XPATH and what is XSLT?

XPATH is an XML query language to select specific parts of an XML document. Using XPATH we can address or filter elements and text in a XML document. For instance a simple XPATH expression like "book/price" states find "price" node which are children of "Invoice" node. XSLT is a rule based language used to transform XML documents in to other file formats. XSLT are nothing but generic transformation rules which can be applied to transform XML document to HTML, CS, Rich text etc.

What is SOAP and how does it relate to XML?
The Simple Object Access Protocol (SOAP) uses XML to define a protocol for the exchange of information in distributed computing environments. SOAP consists of three components: an envelope, a set of encoding rules, and a convention for representing remote procedure calls. Unless experience with SOAP is a direct requirement for the open position, knowing the specifics of the protocol, or how it can be used in conjunction with HTTP, is not as important as identifying it as a natural application of XML.

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Pipes and Cistern

Two pipes A and B can fill a tank in 6 hours and 4 hours respectively. If they are opened on alternate hours and if pipe A s opened first, in how many hours, the tank shall be full?

A large tanker can be filled by two pipes A and B in 60 min and 40 min respectively. How many minutes will it take to fill the tanker from empty state if B is used for first half of the time, and A and B fill it together for the other half?

A tank is filled by 3 pipes with uniform flow. The first two pipes operating simultaneously fill the tank in the same time during which the tank is filled by the third pipe alone. The 2nd pipe fills the tank 5 hours faster than first pipe and 4 hours slower than third pipe. The time required by first pipe is?

Two pipes A and B together can fill a cistern in 4 hours. Had they been opened separately, then B would have taken 6 hours more than A to fill the cistern. How much time will be taken by A to fill the cistern separately?

Two pipes A and B can fill a tank in 24 min and 32 min respectively. If both the pipes are opened simultaneously, after how much time B should be closed so that the tank is full in 18 min?

Two pipes A and B can fill a tank in 36 min and 45 min respectively. A water pipe C can empty the tank in 30 min. First A and B are opened. after 7 min, C is also opened. In how much time, the tank is full?

Two pipes can fill a cistern in 14 hours and 16 hours respectively. The pipes are opened simultaneously and it is found that due to leakage in the bottom it took 32 min more to fill the cistern. When the cistern is full, in what time will the leak empty it?

Bucket P has thrice the capacity as Bucket Q. It takes 60 turns for Bucket P to fill the empty drum. How many turns it will take for both the buckets P and Q, having each turn together to fill the empty drum?

Probability

In a class , 30 % of the students offered English, 20 % offered Hindi and 10 % offered Both.If a student is offered at random, what is the probability that he has offered English or Hindi?

In a lottery ,there are 10 prizes and 25 blanks.A lottery is drawn at random. what is the probability of getting a prize ?

Two dice are thrown simultaneously .what is the probability of getting two numbers whose product is even?

Two diced are tossed the probability that the total score is a prime number?

Two cards are drawn at random from a pack of 52 cards What is the probability that either both are black or both are queens?

Two dice are thrown together .What is the probability that the sum of the number on the two faces is divisible by 4 or 6?

A bag contains 6 white and 4 black balls .Two balls are drawn at random .Find the probability that they are of the same colour?

In a simultaneous throw of a pair of dice,find the probability of getting a total more than 7?

An unbiased die is tossed.Find the probability of getting a multiple of 3?

Problems on Ages

My brother is 3 years elder to me. My father was 28 years of age when my sister was born while my mother was 26 years of age when i was born. If my sister was 4 years of age when my brother was born,then what was the age my father and mother respectively when my brother was born?

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