Page 175 - Data Science class 11
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• It has a heading 'Reminder'.

               • It has a message body.
            But still, the XML above does not do anything. XML is just information wrapped in tags.
            Someone must write a piece of software to send, receive, store, or display it:

            The XML language has no predefined tags. The tags in the example above (like <to> and <from>) are not defined in
            any XML standard. These tags are 'invented' by the author of the XML document.

            4.7.1 is XML a programming Language?
            A programming language consists of grammar rules and its own vocabulary which is used to create computer programs.
            These programs instruct the computer to perform specific tasks. XML does not qualify to be a programming language
            as it does not perform any computation or algorithms. It is usually stored in a simple text file and is processed by
            special software that is capable of interpreting XML.

            4.7.2 Characteristic features of XML

            Following are the characteristic features of XML:
               • It stands for Extensible Markup Language. It is a markup language similar to HTML.
               • It is not a replacement for HTML.

               • It was designed to store and transport data.
               • It is designed to be self-descriptive.
               • This language is a W3C recommendation.
            W3C is an acronym for World Wide Web Consortium. More than 500 companies and institutions are W3C Members.
            Tim Berners-Lee (inventor of the WWW, including HTML, HTTP, and URIs), is the Director of the W3C since 1994.


            4.7.3 Merits and Demerits of using XML
            Following are the advantages that XML provides:

               • Technology agnostic: Being plain text, XML is technology independent. It can be used by any technology for data
              storage and transmission purpose.

               • Human readable: XML uses simple text format. It is human readable and understandable.
               • Extensible: in XML, custom tags can be created and used very easily.
               • Allow Validation: Using XSD, DTD and XML structure can be validated easily.
            Following are the disadvantages of XML usage:

               • Redundant Syntax: Normally, XML file contains a lot of repetitive terms.
               • Verbose: Being a verbose language, XML file size increases the transmission and storage costs.

            4.7.4 Difference Between XML and HtML

            Before we proceed any further, let us understand the key differences between XML and HTML.
               • XML was designed to carry data, i.e. it focuses on what data is whereas HTML was designed to display data, i.e. it
              focuses on appearance of data and the designing of the data presentation.
               • XML tags are not predefined like HTML tags are. Every page on Internet is made up by HTML. The difference in XML
              and HTML is that HTML works with predefined tags like <p>, <h1>, <table>, etc.
            With XML, the author must define both the tags and the document structure.




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