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1 Lecture 15: Working with Extensible Markup Language (XML) The main Topics in this lecture are: - Brief introduction to XML - Some advantages of XML - XML Structure: elements, attributes, entities - What is DTD and XSL? - How you can Read and Write XML file in ASP.Net? - Using XSL with XML Introduction: The World Wide Web Consortium (W3C) is an international consortium where Member organizations, a full-time staff, and the public work together to develop Web standards. W3C was created by Tim Berners-Lee in 1994 who also invented the World Wide Web in In 1998 W3C introduced XML 1.0. XML is a cross-platform, hardware and software independent, text based markup language, which enables you to store data in a structured format by using meaningful tags. XML stores structured data in XML documents that are similar to databases. Notice that unlike Databases, XML documents store data in the form of plain text, which can be used across platforms. In XML document, you specify the structure of the data by creating a DTD or an XML schema. When you include a DTD in an XML document, the software checks the structure of the XML document against the DTD. This process of checking the structure of the XML document is called validating. The software performing the task of validating is called a validating parser. Some advantages of XML are: It is a platform independent language. It is as easy as HTML. 1

2 XML is fully compatible with applications like JAVA, and it can be combined with any application which is capable of processing XML irrespective of the platform it is being used on. XML is an extremely portable language to the extent that it can be used on large networks with multiple platforms like the internet, and it can be used on handhelds or palmtops or PDAs. XML is an extendable language, meaning that you can create your own tags, or use the tags which have already been created. It can be deployed on any network if it is amicable for usage with the application in use. If the application can work along with XML, then XML can work on any platform and has no boundaries. It is also vendor independent and system independent. While data is being exchanged using XML, there will be no loss of data even between systems that use totally different formats. XML Structure: The following code defines the structure of an XML document that will store data related to books: <?xml version="1.0"?> <Books> <Book bid="b001"> <Title> Understanding XML </Title> <Price> $30 </Price> <author> <FirstName> Lily </FirstName> <LastName> Hicks <LastName> </author> </Book> <Book bid="b002"> <Title>.NET Framework </Title> <Price> $45 </Price> <author> <FirstName> Jasmine </FirstName> <LastName> Williams <LastName> </author> </Book> <!-- Add Other Books here- -> </Books> XML Declaration (Processing Instruction) Attribute Element Content Element s Comments 2

3 XML - Elements, Attributes, Entities: tutorial you will learn about Elements, Anatomy of tags, Tag naming rules, Invalid tags, Valid tags, Root and child elements, Attributes, When Do I use Attributes? Entities, Character data sections, Comments and Processing instructions. Elements: Ex: < student > Ali Hammed < /student > An Element consists of three parts 1. Opening Tag < student > 2. Description Ali Hammed 3. Closing Tag < /student > Anatomy of tags All elements must have a beginning and ending tag. The opening tag of an element is written between (< ) less than and ( >)greater than sign example, < student >. The ending tag is written between (< ) less than followed by a (/) forward slash and the ( >)greater than sign example, < /student >. Data between the opening and closing tags of an element are its contents. For example, < student >Mohammed Abas< /student > Here Mohammed Abas is the content of the element. Most of the browsers ignore white spaces between the tags < student > Mohammed Abas < /student > 3

4 Root and child elements The root Element is the first element in a document and it contains all other elements. In the following example student is the root element and all other elements are contained within it (name, roll-number) are child elements. <student> <name> Ali </name> <id> 44 </id> </student> Attributes Attributes give the information about the elements. They can be specified only in the element start tag and their values are enclosed strictly in double quotation-mark. This is unlike HTML where attributes could be in single, double or without quotations. Syntax: < tag attribute = value >description < /tag > Example: < problem size= huge cause= unknown solution= run away > When Do I use Attributes? Unfortunately there is no definite answer to this question. There are many contrarian views on the use of attributes. It is widely accepted belief that attributes are metadata i.e. data about data. In such scenarios use of attributes is recommended. For example, the lang attribute describing the language of the content of the element. Entities: & &amp < < 4

> > ' ' " " Processing instructions Processing instructions are used to pass information to applications which use this information to execute special task. Syntax : <?? > Example <?

5 > > ' ' " " Processing instructions Processing instructions are used to pass information to applications which use this information to execute special task. Syntax : <?? > Example <?xml version= 1.0 encoding= ISO ? > NOTE: Here the version attribute specifies the version of XML being used while encoding gives the encoding format for parsers. XML Technology: Figure 1 illustrates the Technology of XML file. Fig 1: XML Technology XSD - XML Schema Definition DTD - Document Type Definition. XSL - Extensible Stylesheet Language. 5

6 Document Type Definition (DTD): The purpose of a DTD (Document Type Definition) is to define the legal building blocks of an XML document. A DTD defines the document structure with a list of legal elements and attributes. For example, while we haven't gone over the structure of a DTD yet, here is part of a simple one. It states that there is a root element called "family" that has two possible elements within it: "parent" and "child": <!DOCTYPE family [ <!ELEMENT parent (#PCDATA)> <!ELEMENT child (#PCDATA)> ]> If you were to write an XML document based upon that DTD, you could write: <?xml version="1.0" standalone="yes"?> <!DOCTYPE family [ <!ELEMENT parent (#PCDATA)> <!ELEMENT child (#PCDATA)> ]> < family> < parent>judy</parent> < parent>layard</parent> < child>jennifer</child> < child>brendan</child> < /family> This would be a valid XML document. But if I added extra text outside of the < parent> or <child> tags, the document would be invalid until I changed the DTD: < family> This is my family: < parent>judy</parent> < parent>layard</parent> < child>jennifer</child> < child>brendan</child> < /family> 6

7 Extensible Style Sheet Language (XSL): XSL stands for Extensible Stylesheet Language. The World Wide Web Consortium (W3C) started to develop XSL because there was a need for an XML-based Stylesheet Language. XSL = Style Sheets for XML XML does not use predefined tags (we can use any tag-names we like), and therefore the meaning of each tag is not well understood. A< table> tag could mean an HTML table, piece of furniture, or something else - and a browser does not know how to display it. XSL describes how the XML document should be displayed! XSLT Browsers: All major browsers have support for XML and XSLT. Mozilla Firefox: Firefox supports XML, XSLT, and XPath from version 3. Internet Explorer: Internet Explorer supports XML, XSLT, and XPath from version 6. Internet Explorer 5 is NOT compatible with the official W3C XSL Recommendation. Google Chrome: Chrome supports XML, XSLT, and XPath from version 1. Opera: Opera supports XML, XSLT, and XPath from version 9. Opera 8 supports only XML + CSS. Apple Safari: Safari supports XML and XSLT from version 3. Example: <?xml version="1.0" encoding="utf-8"?> <xsl:stylesheet version="1.0" xmlns:xsl=" xmlns:msxsl="urn:schemas-microsoft-com:xslt" exclude-resultprefixes="msxsl"> <xsl:output method="xml" indent="yes"/> <xsl:template match="/"> <html> <body> <h3>customers Information</h3> <table border="1" width="100%"> <tr bgcolor="yellow"> <td>id</td> <td>first Name</td> Name of XML <td>last Name</td> file Root </tr> <xsl:for-each select="newdataset/data"> 7 Name of Child

8 <tr> <td> <xsl:value-of select="id"/> </td> <td> <xsl:value-of select="fname"/> </td> <td> <xsl:value-of select="last_x0020_name"/> </td> </tr> </xsl:for-each> </table> <br/> </body> </html> </xsl:template> </xsl:stylesheet> In V S we have XML Control, you can use it to display your XML file with XSL Name of XML File <asp:xml ID="Xml1" runat="server" DocumentSource="~/data.xml" TransformSource="~/XSLTFile.xslt"></asp:Xml> Name of XSLT File Reading and Writing XML Documents: The.NET Framework provides a class called XmlReader that provides read-only access to XML documents in a forward-only fashion. The XmlReader class allows you to iterate through the document and access the required content rather than raising events. The XmlReader class does not load the entire document in memory, resulting in a small memory footprint. Because it is read-only, it is faster too. Just as XmlReader allows you to read XML documents, a class called XmlWriter allows you to write XML documents. Like XmlReader, it offers write-only functionality. 8

9 DataSet XML IO Methods: ReadXML: to read from file. DataSet ds = new DataSet(); ds.readxml (Server.MapPath ("data.xml")); Example: Consider that you want to represent "books.xml", with a DataSet. For this you can read the "books.xml" file into a DataSet and bind the XML document control to the DataGrid control by adding the following code to the Load event of the page in the.aspx page. protected void btnread_click(object sender, EventArgs e) { DataSet ds = new DataSet(); ds.readxml(mappath("books.xml")); GridView1.DataSource = ds; GridView1.DataBind(); } WriteXML: to write to file. DataSet ds = new DataSet(); SqlDataAdapter da = new SqlDataAdapter("select * from Costumer", con); da.fill(ds,"data"); ds.writexml(server.mappath ("data.xml")); protected void btnwritexml_click(object sender, EventArgs e) { SqlConnection con=new SqlConnection (@"Data Source=.\SQLEXPRESS;AttachDbFilename= DataDirectory \Database.mdf;Integ rated Security=True;User Instance=True"); con.open(); DataSet ds = new DataSet(); SqlDataAdapter da = new SqlDataAdapter("select * from Costumer", con); da.fill(ds,"data"); ds.writexml(server.mappath ("data.xml")); } 9

XSL Languages. Adding styles to HTML elements are simple. Telling a browser to display an element in a special font or color, is easy with CSS.

XSL Languages. Adding styles to HTML elements are simple. Telling a browser to display an element in a special font or color, is easy with CSS. XSL Languages It started with XSL and ended up with XSLT, XPath, and XSL-FO. It Started with XSL XSL stands for EXtensible Stylesheet Language. The World Wide Web Consortium (W3C) started to develop XSL