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Introduction to XML
ISYS 573
HTML vs XML
• HTML is a language specifically designed for displaying information in browser. It doesn’t carry information about the structure of the content held within its page.
• XML (Extensible MarkUp Language) is a language used to represent data in a form that does not rely on any particular proprietary technology. It uses user-defined tags to give meaningful names to data elements. With XML, we separate the data content from the data presentation.
HTML
<body>
<h1>My Favorite Book</h1>
<h1>ISBN - 1-34567-04-01</h1>
<H1>Authors:</H1>
<h3>John Smith</h1>
<h3>Peter Chen</h1>
<h1>Price: $45.00</h1>
<h1>Description: This is a grerat book</h1>
</body>
XML<?xml version="1.0" ?>
<Books>
<Book>
<ISBN>1-34567-04-01</ISBN>
<Authors>
<AuthorName>John Smith</AuthorName>
<AuthorName>Peter Chen</AuthorName>
<AuthorName>David Chao</AuthorName>
</Authors>
<Price> $45.00</Price>
<Description>This is a grerat book</Description>
</Book>
<Book>
<ISBN>1-34567-04-02</ISBN>
<Authors>Adam Smith</Authors>
<Price> $25.00</Price>
<Description>This is a second great book</Description>
</Book>
</Books>
XML Document
• Well-formed documents:– Documents comply with the rules of XML
syntax.
• Valid documents:– Documents that are well-formed and comply
with a XML schema or Document Type Definition (DTD is a file containing the rules used to define the document).
Well-Formed Documents
• There is only one root node.• All elements must have a start tag and an end tag
(except for an empty element, see example below) Elements must be nested correctly.
• If an element has an attribute, the attribute value must be quoted.– An empty element with an attribute:
• <price US=“$49” />
• Note: XML is case sensitive.
XML Documents• The XML declaration:
– <?xml version=“1.0” ?>– Note: xml should be in lower case.
• Namespaces– Define a namespace: xmlns:”uri” where the Uniform
Resource Identifier is a unique identifier and is often a URL.– Use a namespace to make a tag unique:
• <namespace: TagName>
• Elements: – Each start-tag/end-tag pair, with the data that lies between
them, is an element.– Ex. <AuthorName>John Smith</AuthorName>– The start and end tag must be in the same case.
• Attributes: Elements can have attributes. These are values that are passed to the application, but not constitute part of the content of the element. Attributes are included as part of the element’s start tag, and values must be enclosed in quote marks.– <Food healthy=“yes”>Spinach</Food>
– <Food healthy=“yes” tasty=“no”>Carrot</Food>
• Comments:– <!--This is a comment -->
• Processing instructions: These allow documents to contain instructions for applications using XML data.– <?NameOfTargetApplication Instructions for
application?>
Tree View of XML
Books
Book
ISBN Authors Price Description
Book
ISBN Authors Price Description
Author Author Author
Valid Documents
• Well-formed documents that conform to an XML schema or DTD.
• XML parsers are programs that are able to validate an XML document against schema or DTD.
• XML parsers are included in IE5 and Netscapt 6 and onwards.
XML SchemaDefinition of an XML Document
• Namespaces: Allow element names to be qualified to avoid name collisions.
• Complex and simple types:– Elements that contains other elements are complex type.
• Cardinality: – minOccurs: 0 for optional element.– maxOccurs: specified number or unbounded
• Compositor:– Sequence: defines an ordered sequence of subelements.– Choice: defines a choice between several possible elements.
• Constraints:– Uniqueness contraint
VS.Net Tools for XML Document and Schema
• Dataset schema
• XML Schema
• XML Document
Style Sheets
• XSL: Extensible Stylesheet Language
• Tell the browser how to display the XML document.
• With a style sheet, all of the style rules are kept in one file and the source document simply links to this file.
• File extension: .CSS
Benefits of Using Style Sheets
• Improve document clarity: No tags such as <font> in an XML document.
• Allow you to modify the presentation of several pages by altering just one file.
• Allow you to present the same data in different ways for different purposes.
• Reduce download time by caching the style sheet on the client.
• Browser screen structure:– Page
• Area– Block Flow Object: Taking up the whole line.
– In-Line Flow Object: Several in-line objects may be on the same line.
<?xml version="1.0" ?>
<?xml:stylesheet href="books.css" type="text/css" ?><Books><Book><btitle>My Favorite Book</btitle><ISBN>1-34567-04-01</ISBN>
<Authors><AuthorName>John Smith</AuthorName><AuthorName>Peter Chen</AuthorName>
</Authors><Price> $45.00</Price><Description>This is a grerat book</Description>
</Book><Book><btitle>My Second Favorite Book</btitle><ISBN>1-34567-04-02</ISBN>
<Authors>Adam Smith</Authors><Price> $25.00</Price><Description>This is a second great book</Description>
</Book></Books>
btitle {display:block;font-family: Aerial, Helvetica;font-weight: bold;font-size: 20pt;color: #9370db;text-align: center;}
ISBN {display:block;font-family: Aerial, Helvetica;font-weight: bold;font-size: 12pt;color: #c71585;text-align: left;}
Authors {display:inline;font-family: Aerial, Helvetica;font-style: italic;font-size: 10pt;color: #9370db;text-align: left;}
Price {
display:block;
font-family: Aerial, Helvetica;
font-size: 12pt;
color: #ff1010;
text-align: left;
}
Description {
display:block;
font-family: Aerial, Helvetica;
font-size: 12pt;
color: #ff1010;
text-align: left;
}
Styling XML with XSLT
• XSLT: Extensible Stylesheet Language Transforms
• XSLT provides a means of transforming one XML document into HTML or another XML document.
Creating XML From DataSet
• DataSet object:– WriteXML(xml file path and name)– WriteXMLSchema(xml schema path and name)
• Demo:ASPNet/XMLWrite.ASPX
dim strConn as string ="Provider=Microsoft.Jet.OLEDB.4.0;Data Source = c:\sales2k.mdb"
dim objConn as new OledbConnection(strConn)
dim strSQL as string = "select * from customer;"
dim objDataSet as new Dataset()
dim objAdapter as new OledbDataAdapter(strSQL, objConn)
objAdapter.Fill(objDataSet, "Cust")
dim objDataView as new DataView(objDataSet.tables("Cust"))
dgCustomer.Datasource=objDataView
dgCustomer.DataBind()
objDataSet.writeXML("c:\inetpub\wwwroot\testWriteXML.XML")
Reading Data into a DataSet from an XML File
• Dataset object:– ReadXMLSchema(file path and name)– ReadXML(file path and name)
• Demo: ASPNet/XMLRead.aspx
dim objDataSet as new Dataset()
objDataSet.ReadXML("c:\inetpub\wwwroot\testWriteXML.XML")
dim objDataView as new DataView(objDataSet.tables("Cust"))
dgCustomer.Datasource=objDataView
dgCustomer.DataBind()
end sub
