XML Interview Questions and Answers

Below is the list of latest and updated XML interview questions and their answers for fresher’s as well as experienced users. These interview question covers basic and latest version of XML. These XML interview questions will help you to prepare for the interviews, for quick revision and provide strength to your technical skills. XML is the Extensible Markup Language. It improves the functionality of the Web by letting you identify your information in a more accurate, flexible, and adaptable way. It is extensible because it is not a fixed format like HTML (which is a single, predefined markup language).

Best XML Interview Questions and Answers

Here you can find top best XML Interview Questions and Answers for beginners and professionals,XML is actually a metalanguage—a language for describing other languages— which lets you design your own markup languages for limitless different types of documents. XML can do this because it’s written in SGML, the international standard metalanguage for text document markup (ISO 8879).

What is a markup language?

A markup language is a set of words and symbols for describing the identity of pieces of a document (for example ‘this is a paragraph’, ‘this is a heading’, ‘this is a list’, ‘this is the caption of this figure’, etc). Programs can use this with a style sheet to create output for screen, print, audio, video, Braille, etc. Some markup languages (e.g. those used in word processors) only describe appearances (‘this is italics’, ‘this is bold’), but this method can only be used for display, and is not normally re-usable for anything else.

Where should I use XML?

Its goal is to enable generic SGML to be served, received, and processed on the Web in the way that is now possible with HTML. XML has been designed for ease of implementation and for interoperability with both SGML and HTML. Despite early attempts, browsers never allowed other SGML, only HTML (although there were plugins), and they allowed it (even encouraged it) to be corrupted or broken, which held development back for over a decade by making it impossible to program for it reliably.

Who is responsible for XML?

XML is a project of the World Wide Web Consortium (W3C), and the development of the specification is supervised by an XML Working Group. A Special Interest Group of co-opted contributors and experts from various fields contributed comments and reviews by email.

Give few examples of types of applications that can benefit from using XML.

There are literally thousands of applications that can benefit from XML technologies. The point of this question is not to have the candidate rattle off a laundry list of projects that they have worked on, but, rather, to allow the candidate to explain the rationale for choosing XML by citing a few real world examples. For instance, one appropriate answer is that XML allows content management systems to store documents independently of their format, which thereby reduces data redundancy.

What is DOM and how does it relate to XML?

The Document Object Model (DOM) is an interface specification maintained by the W3C DOM Workgroup that defines an application independent mechanism to access, parse, or update XML data. In simple terms it is a hierarchical model that allows developers to manipulate XML documents easily Any developer that has worked extensively with XML should be able to discuss the concept and use of DOM objects freely.

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.

Why not just carry on extending HTML?

HTML was already overburdened with dozens of interesting but incompatible inventions from different manufacturers, because it provides only one way of describing your information. XML allows groups of people or organizations to question C.13, create their own customized markup applications for exchanging information in their domain (music, chemistry, electronics, hill-walking, finance, surfing, petroleum geology, linguistics, cooking, knitting, stellar cartography, history, engineering, rabbit-keeping, question C.19, mathematics, genealogy, etc).

Can you walk us through the steps necessary to parse XML documents?

Superficially, this is a fairly basic question. However, the point is not to determine whether candidates understand the concept of a parser but rather have them walk through the process of parsing XML documents step-by-step. Determining whether a non-validating or validating parser is needed, choosing the appropriate parser, and handling errors are all important aspects to this process that should be included in the candidate’s response.

Give some examples of XML DTDs or schemas that you have worked with.

Although XML does not require data to be validated against a DTD, many of the benefits of using the technology are derived from being able to validate XML documents against business or technical architecture rules. Polling for the list of DTDs that developers have worked with provides insight to their general exposure to the technology.

How would you build a search engine for large volumes of XML data?

The way candidates answer this question may provide insight into their view of XML data. For those who view XML primarily as a way to denote structure for text files, a common answer is to build a full-text search and handle the data similarly to the way Internet portals handle HTML pages. Others consider XML as a standard way of transferring structured data between disparate systems.

Does XML replace HTML?

No. XML itself does not replace HTML. Instead, it provides an alternative which allows you to define your own set of markup elements. HTML is expected to remain in common use for some time to come, and the current version of HTML is in XML syntax. XML is designed to make the writing of DTDs much simpler than with full SGML.

How does XML handle white-space in my documents?

All white-space, including line breaks, TAB characters, and normal spaces, even between ‘structural’ elements where no text can ever appear, is passed by the parser unchanged to the application (browser, formatter, viewer, converter, etc), identifying the context in which the white-space was found (element content, data content, or mixed content, if this information is available to the parser, eg from a DTD or Schema).

How can I make my existing HTML files work in XML?

Either convert them to conform to some new document type (with or without a DTD or Schema) and write a stylesheet to go with them; or edit them to conform to XHTML. It is necessary to convert existing HTML files because XML does not permit end-tag minimisation (missing, etc), unquoted attribute values, and a number of other SGML shortcuts which have been normal in most HTML DTDs.

Is there an XML version of HTML?

Yes, the W3C recommends using XHTML which is ‘a reformulation of HTML 4 in XML 1.0’. This specification defines HTML as an XML application, and provides three DTDs corresponding to the ones defined by HTML 4.* (Strict, Transitional, and Frameset).

What’s a Document Type Definition (DTD) and where do I get one?

A DTD is a description in XML Declaration Syntax of a particular type or class of document. It sets out what names are to be used for the different types of element, where they may occur, and how they all fit together. (A question C.16, Schema does the same thing in XML Document Syntax, and allows more extensive data-checking.)

Does XML let me make up my own tags?

No, it lets you make up names for your own element types. If you think tags and elements are the same thing you are already in considerable trouble: read the rest of this question carefully.

How do I create my own document type?

Document types usually need a formal description, either a DTD or a Schema. Whilst it is possible to process well-formed XML documents without any such description, trying to create them without one is asking for trouble. A DTD or Schema is used with an XML editor or API interface to guide and control the construction of the document, making sure the right elements go in the right places.

How do I get XML into or out of a database?

Ask your database manufacturer: they all provide XML import and export modules to connect XML applications with databases. In some trivial cases there will be a 1:1 match between field names in the database table and element type names in the XML Schema or DTD, but in most cases some programming will be required to establish the desired match.

How will XML affect my document links?

The linking abilities of XML systems are potentially much more powerful than those of HTML, so you’ll be able to do much more with them. Existing href-style links will remain usable, but the new linking technology is based on the lessons learned in the development of other standards involving hypertext, such as TEI and HyTime, which let you manage bidirectional and multi-way links, as well as links to a whole element or span of text (within your own or other documents) rather than to a single point.

How does XML handle metadata?

Because XML lets you define your own markup languages, you can make full use of the extended hypertext features of XML (see the question on Links) to store or link to metadata in any format (eg using ISO 11179, as a Topic Maps Published Subject, with Dublin Core, Warwick Framework, or with Resource Description Framework (RDF), or even Platform for Internet Content Selection (PICS)).

Can I use JavaScript, ActiveX, etc in XML files?

This will depend on what facilities your users’ browsers implement. XML is about describing information; scripting languages and languages for embedded functionality are software which enables the information to be manipulated at the user’s end, so these languages do not normally have any place in an XML file itself, but in stylesheets like XSL and CSS where they can be added to generated HTML.

How do I use graphics in XML?

Graphics have traditionally just been links which happen to have a picture file at the end rather than another piece of text. They can therefore be implemented in any way supported by the XLink and XPointer specifications (see question C.18, ‘How will XML affect my document links?’), including using similar syntax to existing HTML images.

When should I use a CDATA Marked Section?

You should almost never need to use CDATA Sections. The CDATA mechanism was designed to let an author quote fragments of text containing markup characters (the open-angle-bracket and the ampersand), for example when documenting XML (this FAQ uses CDATA Sections quite a lot, for obvious reasons).

What are the special characters in XML?

For normal text (not markup), there are no special characters: just make sure your document refers to the correct encoding scheme for the language and/or writing system you want to use, and that your computer correctly stores the file using that encoding scheme. See the question on non-Latin characters for a longer explanation.

Who can create an XML namespace?

Anybody can create an XML namespace — all you need to do is assign a URI as its name and decide what element type and attribute names are in it. The URI must be under your control and should not be being used to identify a different XML namespace, such as by a coworker.

What is the relationship between XML namespaces and the XML 1.0 recommendation?

Although the XML 1.0 recommendation anticipated the need for XML namespaces by noting that element type and attribute names should not include colons, it did not actually support XML namespaces. Thus, XML namespaces are layered on top of XML 1.0. In particular, any XML document that uses XML namespaces is a legal XML 1.0 document and can be interpreted as such in the absence of XML namespaces.

How do I undeclare the default XML namespace?

To “undeclare” the default XML namespace, you declare a default XML namespace with an empty (zero-length) name (URI). Within the scope of this declaration, unprefixed element type names do not belong to any XML namespace.

Why are special attributes used to declare XML namespaces?

I don’t know the answer to this question, but the likely reason is that the hope that they would simplify the process of moving fragments from one document to another document. An early draft of the XML namespaces recommendation proposed using processing instructions to declare XML namespaces.

How can I validate an XML document that uses XML namespaces?

When people ask this question, they usually assume that validity is different for documents that use XML namespaces and documents that don’t. In fact, it isn’t — it’s the same for both. Thus, there is no difference between validating a document that uses XML namespaces and validating one that doesn’t.

How are universal names represented?

There is no standard way to represent a universal name. However, three representations are common. The first representation keeps the XML namespace name (URI) and the local name separate. For example, many DOM level 1 implementations have different methods for returning the XML namespace name (URI) and the local name of an element or attribute node.