XML for Computer Science and MCA students

What is XML? Explain its features.

• XML stands for Extensible Markup Language.
• It is a markup language like HTML.
• It was designed to store and transport data.
• It has no predefined tags like HTML.
• XML simplifies the data sharing, data transport, platform changes and data availability.
• It stores the data in a plain text.
• It provides a software and hardware way of storing, transporting and sharing data.

• It provides a software and hardware way of storing, transporting and sharing data.
• It separates data from HTML.
• It increases data availability.
• It can be used to create new Internet languages like XHTML, WSDL, WAP, WML etc.
• It is heavily used as a format for document storage and processing both online and offline.
• It does not allow references to external data entities.
• It does not allow empty comment declaration.
• It is extensible, because it only specifies the structural rules of tags. No specification on tags them self.

• XSL stands for Extensible Style Sheet Language.
• XSL is the future of XML display.
• It is a special declaration in XML for linking with the stylesheets.
• XSL is an XML-based languages for expressing the Style Sheets.
• You can make context-sensitive display decisions using with XSL.
• For example, you could automatically display the document one way in a Web browser and another on a PDA.
• XSL can also transform XML into HTML, so that older browsers can view XML documents.

• It is a language which transforms XML documents into XHTML documents or to other XML documents.
• XSLT stands for Extensible Stylesheet Language Transformations.
• It uses XPATH to navigate in XML documents.
• XSLT uses XPATH to identify subsets of the source document tree and perform calculations.
• XSLT language is used for transforming XML documents into XHTML documents.
• It also transforms XML into another XML document.
• It specifies a language definition for XML data presentation and data transformations.
• It is used to describe how to transform the source tree or data structure of an XML document into the result tree for a new XML document.
It has two attributes:
1. Type: It indicates the type of file being linked to. It will be using the value 'text/xsl' to specify XSLT.
2. href: It indicates the location of the file. If you saved your XSLT and XML file in the same directory, you can simply use the XSLT filename.

• It is a mechanism to avoid name conflicts by differentiating elements or attributes within an element XML document.
• It is used to avoid element name conflict in an XML document.
• It is declared using the reserved XML attribute.
• This attribute name must be started with 'xmlns'.

• In the above example, Namespace Prefix is 'cont' and Namespace Identifiers is 'www.careerride.com'.
• It specifies that the element name and attribute names with 'cont' prefix belongs to 'www.careerride.com' namespace.
• The elements name are defined by the developer so there is a chance to conflict in name of the elements.
• To avoid these types of confliction, XML namespace is used.
• XML namespace provides a method to avoid element name conflict.

Give difference between DTD and XML schema.

• It is a set of markup declarations which define a document type for the markup language, such as SGML, XML, HTML.
• DTD stands for Document Type Definition.
It supports two types of data:
1. PCDATA (Parsed Character Data): XML parsers normally parse all the text in an XML document.
2. CDATA (Character Data): It is used about text data that should not be parsed by the XML parser.
• It defines the elements, attributes, ordering and nesting elements.
• DTD lacks strong typing capabilities and it has no way of validating the content to data types.
• It does not define the order for child elements.
• It does not support data types.

• It is the structure of an XML document.
• It supports numeric, Boolean and String data types.
• It is suitable for applications that developed in a programming language.
• Schema supports custom data types.
• It supports encapsulation and inheritance concepts.
• Schema supports for WEB services, XSLT.
• It defines order for child elements.

Explain DOM parser.

• It is a cross-platform and language independent.
• DOM is an open standard.
• It is an official recommendation of the World Wide Web Consortium (W3C).
• The HTML DOM API specializes and adds the functionality to relate to HTML documents and elements.
• It addresses the issues of backwards compatibility with the Level 0 of DOM.

• It provides mechanisms for common and frequent operations on HTML documents.
• It is a programming interface for HTML and XML documents.
• The DOM provides a structured representation of the document.
• It provides a representation of the document as a structured group of nodes and objects which have properties and methods.
• DOM defines a way that the structure can be accessed from programs so that they can change the document structure, style and content.
• It provides interfaces on components of a tree which is a DOM document.
• It creates a tree structure in memory from the input document and then waits for requests from the client.
• It always serves the client application with the entire document no matter how much is actually needed by the client.
• The XML file is arranged in a tree fashion.
• DOM supports random access to the data of an XML file.

Explain DTD in detail with its example.

• It is a set of markup declarations which define a document type for the markup language, such as SGML, XML, HTML.
• DTD stands for Document Type Definition.
It supports two types of data:
1. PCDATA
2. CDATA

1. PCDATA (Parsed Character Data): XML parsers normally parse all the text in an XML document.
2. CDATA (Character Data): It is used about text data that should not be parsed by the XML parser.
• It defines the elements, attributes, ordering and nesting elements.
• DTD lacks strong typing capabilities and it has no way of validating the content to data types.
• It does not define the order for child elements.
• It does not support data types.

Explain SOAP.

• XML Web Service is a unit of code that can be accessed independent of platforms and systems.
• These services are the web application components.
• They are used to interchange data between different systems in different machines for interoperability using HTTP protocols.
• Requests are made and responses are returned in the form of XML as XML is a language and platform independent.
• It exposes useful functionality to web users through a standard web protocol.
• It provides a way to describe their interfaces in enough detail to allow a user to build a client application to talk to them.
• These services are registered so that potential users can find them easily.

• SOAP stands for Simple Object Access Protocol.
• It is a communication protocol that communicates between applications.
• It is a platform and language independent.
• It can run on any operating system.
• It describes how to encode an HTTP header and an XML file for making communication between two computers.
• SOAP is an XML-based protocol that enables two components to communicate each other.
• It has the rules to translate platform specific data into the XML format.

• It defines its own security which is known as Web Service Security.
• It has a benefit to allow server firewalls.
• It can be written in any programming language and executed on any platform.
• Web services are based on SOAP protocol in order to expose their functionality to disparate application and platform.

• It consumes more bandwidth and resource.
• It is slow.
• It does not have any other mechanism to discover the service.