Lecture E-Commerce - Chapter 19: eXtensible Markup Language (XML) (part II). In this chapter students will be able to: XML elements are extensible, XML attributes, XML namespaces, XML encoding, viewing XML files.
CSC 330 E-Commerce Teacher Ahmed Mumtaz Mustehsan GM-IT CIIT Islamabad Virtual Campus, CIIT COMSATS Institute of Information Technology T2-Lecture-4 eXtensible Markup Language (XML) Part - II For Lecture Material/Slides Thanks to: www.w3schools.com Objectives XML Elements are extensible XML Attributes XML Namespaces XML Encoding Viewing T2-Lecture-4 XML Files Ahmed Mumtaz Mustehsan www.w3schools.com XML Elements are Extensible XML elements can be extended to carry more information Look at the following XML example: ◦ mumtaz tariq Don't forget to attend party on weekend! Let's imagine that we created an application that extracted the , , and elements from the XML document to produce this output: Message To: Mumtaz From: Tariq Don't forget to attend party on weekend! T2-Lecture-3 Ahmed Mumtaz Mustehsan www.w3schools.com XML Elements are Extensible… Imagine that the author of the XML document added some extra information to it: Message To: Mumtaz From: Tariq 2008-01-10 Don't forget to attend party on Mumtaz weekend! Tariq Reminder Don't forget to attend party on weekend! Should the application break or crash? No The application should still be able to find the , , and elements in the XML document and produce the same output One of the beauty of XML, is that it can be extended without breaking applications T2-Lecture-3 Ahmed Mumtaz Mustehsan www.w3schools.com XML Attributes XML Attributes In HTML, attributes provide additional information about elements: XML elements can have attributes, just like HTML Attributes often provide information that is not a part of the data but it is information about data Example computer.gif The file type is irrelevant to the data, but can be important to the software that wants to manipulate the element: T2-Lecture-4 Ahmed Mumtaz Mustehsan www.w3schools.com XML Attributes Must be Quoted Attribute values must always be quoted Either single or double quotes can be used Example: For a person's sex, the person element can be written like this: or like this: T2-Lecture-4 Ahmed Mumtaz Mustehsan www.w3schools.com XML Attributes Must be Quoted If the attribute value itself contains double quotes we can use single quotes Example: Amna Atif Example-2: female Amna Atif 10 T2-Lecture-4 Ahmed Mumtaz Mustehsan www.w3schools.com XML Encoding The first line in an XML document is called the prolog: The prolog is optional Normally it contains the XML version number It can also contain information about the encoding used in the document This prolog specifies UTF-8 encoding: The XML standard states that all XML software must understand both UTF-8 and UTF-16 UTF-8 is the default for documents without encoding information In addition, most XML software systems understand encodings like ISO-8859-1, Windows-1252, and ASCII 31 T2-Lecture-4 Ahmed Mumtaz Mustehsan www.w3schools.com XML Errors Most often, ◦XML documents are created on one computer ◦uploaded to a server on a second computer, ◦displayed by a browser on a third computer If the encoding is not correctly interpreted by all the three computers, the browser might display meaningless text, or you might get an error message Example: “This XML file does not appear to have any style information associated with it.” 32 T2-Lecture-4 Ahmed Mumtaz Mustehsan www.w3schools.com Conclusion When you write an XML document: Use an XML editor that supports encoding Make sure you know what encoding the editor uses Describe the encoding in the encoding attribute UTF-8 is the safest encoding to use which is a web standard 33 T2-Lecture-4 Ahmed Mumtaz Mustehsan www.w3schools.com Viewing XML Files Viewing XML Files Raw XML files can be viewed in all major browsers Don't expect XML files to be displayed as HTML pages - mumtaz tariq Reminder Don't forget me this weekend! The XML document will be displayed with color-coded root and child elements A plus (+) or minus sign (-) to the left of the elements can be clicked to expand or collapse the element structure To view the raw XML source (without the + and signs), select "View Page Source" or "View Source" from the browser menu Note: In Safari, only the element text will be displayed To view the raw XML, you must right click the page and select "View Source" 35 T2-Lecture-4 Ahmed Mumtaz Mustehsan www.w3schools.com Viewing an Invalid XML File If an erroneous XML file is opened, some browsers might report the error, some may display it incorrectly Try 36 to open this XML file in different browsers: T2-Lecture-4 Ahmed Mumtaz Mustehsan www.w3schools.com Why Does XML Display Like This? XML documents not carry information about how to display the data Since XML tags are "invented" by the author of the XML document, browsers not know if a tag like describes an HTML table or a dining table Without any information about how to display the data, most browsers will just display the XML document as it is 37 T2-Lecture-4 Ahmed Mumtaz Mustehsan www.w3schools.com A Section of the XML file The second line links the XML file to the CSS file: Empire Burlesque Bob Dylan USA Columbia 10.90 1985 Hide your heart Bonnie Tyler UK CBS Records 9.90 1988 38 T2-Lecture-4 Ahmed Mumtaz Mustehsan www.w3schools.com Displaying your XML Files with CSS It is possible to use CSS to format an XML document Below is an example of how to use a CSS style sheet to format an XML document: Take a look at this XML file: The CD catalog Then look at this style sheet: The CSS file Finally, view: The CD catalog formatted with the CSS file 39 T2-Lecture-4 Ahmed Mumtaz Mustehsan www.w3schools.com XML Technologies Some XML Technologies: •XML XSLT •XML Xpath •XML Xlink •XML Xpointer •XML Xquery •Recommended by W3C 40 T2-Lecture-4 Ahmed Mumtaz Mustehsan www.w3schools.com XML - XSLT Displaying XML with XSLT XSLT (eXtensible Stylesheet Language Transformations) is the recommended style sheet language for XML XSLT is far more sophisticated than CSS Elements and attributes can be added/removed Elements can also be rearranged and sorted, perform tests and make decisions about which elements to hide and display, etc XSLT uses XPath to find information in an XML document 41 T2-Lecture-4 Ahmed Mumtaz Mustehsan www.w3schools.com XML - Xpath XPath is Used in XSLT XPath is a syntax for defining parts of an XML document XPath uses path expressions to navigate in XML documents XPath contains a library of standard functions XPath is a major element in XSLT XPath is also used in XQuery, XPointer and XLink 42 T2-Lecture-4 Ahmed Mumtaz Mustehsan www.w3schools.com XML - XLink XLink is used to create hyperlinks within XML documents Any element in an XML document can behave as a link XLink supports simple links (like HTML) and extended links (for linking multiple resources together) With XLink, the links can be defined outside the linked files XLink is a W3C Recommendation 43 T2-Lecture-4 Ahmed Mumtaz Mustehsan www.w3schools.com XML - XPointer XPointer allows the links to point to specific parts of an XML document XPointer uses XPath expressions to navigate in the XML document XPointer is a W3C Recommendation 44 T2-Lecture-4 Ahmed Mumtaz Mustehsan www.w3schools.com The End XML Part-II T2-Lecture-4 Thank You T2-Lecture-4 Ahmed Mumtaz Mustehsan www.w3schools.com 45 ... T2 -Lecture- 4 Ahmed Mumtaz Mustehsan www.w3schools.com UTF-8 - The Web Standard UTF-8 is the standard character encoding on the web It (UTF-8) is the default character encoding for: HTML-5,.. .eXtensible Markup Language (XML) Part - II For Lecture Material/Slides Thanks to: www.w3schools.com Objectives XML Elements are extensible XML Attributes XML... information In addition, most XML software systems understand encodings like ISO-885 9-1 , Windows-1252, and ASCII 31 T2 -Lecture- 4 Ahmed Mumtaz Mustehsan www.w3schools.com