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Dive into the world of XML with this comprehensive guide by Eric Taylor. Understand the basics of XML, its importance, language details, incorporation into business applications, and practical examples. Learn about XML syntax, structure, validation, and transformation using XSLT. Discover the power of XML in simplifying data sharing and extending legacy systems. Perfect for beginners and experienced developers alike.
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XML: The new standard -Eric Taylor
Overview • What is XML? • Why use XML? • Details of the language • Incorporating XML • Business Application • Small Assignment
What is XML? • eXtensible Markup Language • Markup language like HTML • Designed to carry data, not display it • W3C recommended • World Wide Web Consortium
What is XML? • Plain text. • What does it do? • Not an independent language. • The Design: • Compatibility • Straightforward • Fast • Wide support
Why use XML? • Simplifies HTML changes based on data changes. • Standardized data sharing. • Too many possibilities without it. • Incompatible applications not affected. • Hardware/Software independent • Minor exceptions
Language Details • Tag based. • Unlike HTML, all tags are user-defined. • <random_tag_name> data_to_be_stored </random_tag_name> • Data stored between tags, or within tags as attributes. • Attributes are normally used for information that describes the tag itself, not necessarily the information you want to store. • Ex: <book internal_id=“11421” />
Language Details • Tree structure • <library> • <book internal_id=“11421”> • <name> A Game of Thrones </name> • <isbn> 123456789 </isbn> • … • </book> • <book internal_id=“11422”> • <name> A Clash of Kings </name> • <isbn> 123456788 </isbn> • … • </book> • </library>
Language Details Example 2: From w3schools.com
Language Details • Syntax Details: • Case sensitive tags. • Defined values • Quoted values • Nesting: bold, italic, etc… • Naming rules
Language Details • Namespaces: • Think of <include> statements. • Allows reference to different types of data with similar names. • Allows reference to custom data-types. • Integer, decimal, string fields, etc, with restrictions and/or patterns.
Language Details <root> <h:table xmlns:h="http://www.w3.org/TR/html4/"> <h:tr> <h:td>Apples</h:td> <h:td>Bananas</h:td> </h:tr> </h:table> <f:table xmlns:f="http://www.w3schools.com/furniture"> <f:name>African Coffee Table</f:name> <f:width>80</f:width> <f:length>120</f:length> </f:table> </root>
Language Details • Validation: • How do we know an XML document is correct? • How do we know we are getting the information we want? • “Well formed” • Adheres to syntax rules • Easily done with XML software and processing code. • Validity: • Answers the “are we getting what we want?” question. • Follows the given XML schema (known as an XSD).
Language Details • What is a schema (XSD)? • XML file with the extension .xsd • Dictates the allowed structure of a corresponding XML file. • Defines possible fields, field values, etc. • Used in process of ‘Schema Validations’. • Pass or fail check if the corresponding XML file contains the appropriate information. • Structure and data types, NOT content (elements vs. their value).
Language Details XML File: <note> <to>Tove</to> <from>Jani</from> <heading>Reminder</heading> <body>Don't forget me this weekend!</body> </note> XSD File: <xs:element name="note"> <xs:complexType> <xs:sequence> <xs:element name="to" type="xs:string"/> <xs:element name="from" type="xs:string"/> <xs:element name="heading" type="xs:string"/> <xs:element name="body" type="xs:string"/> </xs:sequence> </xs:complexType> </xs:element>
Incorporating XML • Parsing XML to use it: • DOM (Document Object Model). • Standard way for accessing and manipulating XML documents. • xmlDoc - the XML document created by the parser. • getElementsByTagName(“tag_name")[0] - the first <tag_name> element • childNodes[0] - the first child of the <tag_name> element (the text node) • nodeValue - the value of the node (the text itself) • some_variable=xmlDoc.getElementsByTagName(“book”)[0].childNodes[0].nodeValue;
Incorporating XML • Parsing commonly done via JavaScript in web applications. • Java can import libraries to use the standard DOM for parsing.
Incorporating XML From w3schools.com
Incorporating XML • XSLT used to display and format XML. • Basically “transforming XML to HTML before it is displayed by the browser”.
XML in Practice • Allows for extension to legacy systems. • Create a new ‘front end’ process to make the data match to legacy. • Things to consider: • Use similar XML software to eliminate small differences. • Establish a common schema • Schema validations on both ends of transmission. • Business logic to process the data.
Small Assignment: • Download the 30 day free trial of XML Spy. (very quick installation) • Go through the ‘getting started’ tutorial. • Create a sample schema based on some of the previous examples. • Create an XML document based on the schema, and validate. • Load the XML file into an HTML document and display the values. • Use Tomcat, or any IDE with a preview function.
References http://www.tizag.com/xmlTutorial/ www.w3schools.com Amiano, Mitch, Conrad D'cruz, Kay Ethier, and Michael D. Thomas. XML Problem-Design-Solution. Indianapolis: Wiley Inc, 2006.
