Logo F2FInterview

XML Interview Questions

Q   |   QA
‹‹ previous1234567891011

  • XML stands for EXtensible Markup Language
  • XML is a markup language much like HTML
  • XML was designed to carry data, not to display data
  • XML tags are not predefined. You must define your own tags
  • XML is designed to be self-descriptive
  • XML is a W3C Recommendation

Ans 1:

XML is not a replacement for HTML.

XML and HTML were designed with different goals:

  • XML was designed to transport and store data, with focus on what data is
  • HTML was designed to display data, with focus on how data looks

HTML is about displaying information, while XML is about carrying information.

Ans 2:

XMLHTML

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

XML is used in many aspects of web development, often to simplify data storage and sharing.

XML Separates Data from HTML

If you need to display dynamic data in your HTML document, it will take a lot of work to edit the HTML each time the data changes.

With XML, data can be stored in separate XML files. This way you can concentrate on using HTML for layout and display, and be sure that changes in the underlying data will not require any changes to the HTML.

With a few lines of JavaScript code, you can read an external XML file and update the data content of your web page.

XML Simplifies Data Sharing

In the real world, computer systems and databases contain data in incompatible formats.

XML data is stored in plain text format. This provides a software- and hardware-independent way of storing data.

This makes it much easier to create data that can be shared by different applications.

XML Simplifies Data Transport

One of the most time-consuming challenges for developers is to exchange data between incompatible systems over the Internet.

Exchanging data as XML greatly reduces this complexity, since the data can be read by different incompatible applications.

XML Simplifies Platform Changes

Upgrading to new systems (hardware or software platforms), is always time consuming. Large amounts of data must be converted and incompatible data is often lost.

XML data is stored in text format. This makes it easier to expand or upgrade to new operating systems, new applications, or new browsers, without losing data.

XML Makes Your Data More Available

Different applications can access your data, not only in HTML pages, but also from XML data sources.

With XML, your data can be available to all kinds of "reading machines" (Handheld computers, voice machines, news feeds, etc), and make it more available for blind people, or people with other disabilities.

XML is Used to Create New Internet Languages

A lot of new Internet languages are created with XML.

Here are some examples:

  • XHTML
  • WSDL for describing available web services
  • WAP and WML as markup languages for handheld devices
  • RSS languages for news feeds
  • RDF and OWL for describing resources and ontology
  • SMIL for describing multimedia for the web

If Developers Have Sense

If they DO have sense, future applications will exchange their data in XML.

The future might give us word processors, spreadsheet applications and databases that can read each other's data in XML format, without any conversion utilities in between.

XML is verbose and it can be 4-6 times larger in size compared to a csv or a tab delimited file. If your network lacked bandwidth and/or your content is too large and network throughput is vital to the application then you may consider using a csv or tab delimited format instead of an XML.

SAX parser

  • A SAX (Simple API for XML) parser does not create any internal structure. Instead, it takes the occurrences of components of an input document as events (i.e., event driven), and tells the client what it reads as it reads through the input document.
  • A SAX parser serves the client application always only with pieces of the document at any given time.
  • A SAX parser, however, is much more space efficient in case of a big input document (because it creates no internal structure). What’s more, it runs faster and is easier to learn than DOM parser because its API is really simple. But from the functionality point of view, it provides a fewer functions, which means that the users themselves have to take care of more, such as creating their own data structures.
  • Use SAX parser when

    • Input document is too big for available memory.
    • When only a part of the document is to be read and we create the data structures of our own.
    • If you use SAX, you are using much less memory and performing much less dynamic memory allocation.
  • SAX Parser example: Xerces, Crimson etc Use JAXP (Java API for XML Parsing) which enables applications to parse and transform XML documents independent of the particular XML parser. Code can be developed with one SAX parser in mind and later on can be changed to another SAX parser without changing the application code.

DOM parser

  • A DOM (Document Object Model) parser creates a tree structure in memory from an input document and then waits for requests from client.
  • A DOM parser always serves the client application with the entire document no matter how much is actually needed by the client.
  • A DOM parser is rich in functionality. It creates a DOM tree in memory and allows you to access any part of the document repeatedly and allows you to modify the DOM tree. But it is space inefficient when the document is huge, and it takes a little bit longer to learn how to work with it.
  • Use DOM when
    • Your application has to access various parts of the document and using your own structure is just as complicated as the DOM tree.
    • Your application has to change the tree very frequently and data has to be stored for a significant amount of time.
  • DOM Parser example: XercesDOM, SunDOM, OracleDOM etc. Use JAXP (Java API for XML Parsing) which enables applications to parse and transform XML documents independent of the particular XML parser. Code can be developed with one DOM parser in mind and later on can be changed to another DOM parser without changing the application code.

‹‹ previous1234567891011

In order to link this F2FInterview's page as Reference on your website or Blog, click on below text area and pres (CTRL-C) to copy the code in clipboard or right click then copy the following lines after that paste into your website or Blog.

Get Reference Link To This Page: (copy below code by (CTRL-C) and paste into your website or Blog)
HTML Rendering of above code: